Jasmine's Biology Blog

Thursday, May 29, 2014

Standards 1-9

Standard 1

SP 1/1: I can ask questions that arise from careful observation of phenomena, or unexpected results, to clarify and/or seek additional information.

SP 1/2: I can ask questions to determine relationships, including quantitative relationships, between independent and dependent variables.

SP 1/3: I can evaluate a question to determine if it is testable, relevant, and the interpretation of a data set.

Projects/Labs:

Semester 1:

Milk in Motion:

http://nothingyouneedtoknownows.tumblr.com/post/79140032361/milk-in-motion

pGlo Lab:

http://nothingyouneedtoknownows.tumblr.com/post/69851975882/pglo-lab

Semester 2:

Enzyme Lab:

http://nothingyouneedtoknownows.blogspot.com/2014/05/enzyme-lab_26.html

Cell Respiration Lab:

http://nothingyouneedtoknownows.blogspot.com/2014/05/cell-respiration-lab.html

In the Enzyme Lab and the Cell Respiration Lab I was able to ask questions and predict what was going to happen in our experiments. We used our knowledge on enzymes and cell respiration to conduct two hypothesis. For the enzyme lab, we think that different fresh fruit is going to have a different reaction with the collagen because they have different kinds of enzymes. For the yeast lab, we think that the heating plate will create the most carbon dioxide.

Standard 2

SP 2/1: I can develop, revise, and/or use a model based on evidence to illustrate and/or predict the relationships between systems or between components of a system

SP 2/2: I can develop and/or use a model (including mathematical and computational) to generate data to support explanations, predict phenomena, analyze systems, and/or solve problems.

Projects/Labs:

Semester 1:

Protein Synthesis Blog:

http://nothingyouneedtoknownows.blogspot.com/2013/12/protein-synthesis.html

Oral Cancer Project:

https://docs.google.com/document/d/1X3y6zyUxJ2gWPuj-ECteZlnH6m3oUWqbVHc3T8KTm0I/edit

Semester 2:

Forensics Quiz:

http://nothingyouneedtoknownows.blogspot.com/2014/02/forensics-quiz.html

The Forensics Quiz demonstrates this standard because using the muscular and skeletal models I found, I visualized the situation more clearly and understood the external and internal part of the body. I also applied these skills to find different scenarios. Using the model and drawings, I was able to see more clearly how the organs could have been affected and what damages could they lead to. Then I was able to hypothesize three possibilities of the victim’s death.

Standard 3

SP 3/1: I can plan an investigation or test a design individually and collaboratively to produce data to serve as the basis for evidence as part of building and revising models, supporting explanations for phenomena, or testing solutions to problems. Consider possible confounding variables or effects and evaluate the investigation’s design to ensure variables are controlled.

SP 3/2: I can plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.

SP 3/3: I can make directional hypotheses that specify what happens to a dependent variable when an independent variable is manipulated.

Projects/Labs:

Semester 1:

Milk in Motion Lab:

http://nothingyouneedtoknownows.tumblr.com/post/79140032361/milk-in-motion

pGlo Lab:

http://nothingyouneedtoknownows.tumblr.com/post/69851975882/pglo-lab

Semester 2:

Enzyme Lab:

http://nothingyouneedtoknownows.blogspot.com/2014/05/enzyme-lab_26.html

Cell Respiration Lab:

http://nothingyouneedtoknownows.blogspot.com/2014/05/cell-respiration-lab.html

In the Enzyme Lab and Cell Respiration Lab, we understood how both labs worked, conducted our own hypothesis, and tested them out. We planned out what kind of materials we were going to use and what kind of method we were going to use to test it. In the Enzyme Lab, we used different fruits as materials, with the regular jello as a control. In the Cell Respiration Lab, we used a number of different materials, and planned out the experiment accordingly.

Standard 4

SP 4/1: I can analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution.

SP 4/2: I can apply concepts of statistics and probability (including determining function fits to data, slope, intercept, and correlation coefficient for linear fits) to scientific questions and problems, using digital tools when feasible.

SP 4/3: I can compare and contrast various types of data sets (e.g., self generated, archival) to examine consistency of measurements and observations.

Projects/Labs:

Semester 1:

Oral Cancer Project:

https://docs.google.com/document/d/1X3y6zyUxJ2gWPuj-ECteZlnH6m3oUWqbVHc3T8KTm0I/edit

Semester 2:

Transpiration Lab:

http://nothingyouneedtoknownows.blogspot.com/2014/05/transpiration-lab.html

In the transpiration lab, we were able to interpret results from the data we collected. There were different results from different plants and conditions. With the experiment stimulation, we were able to see how different plants reacted to different temperature, light and air using a photometer. The amount of water vapor collected varies in different kinds of plants. According to the data, we know that wind has the greatest effect on the amount of water during transpiration. With a higher level of wind, the transpiration increases because the wind blows away water vapor from the plant causing a higher rate for transpiration. At last, we could interpret from the data that different species of plants transpire at different rate because their leaves and pores differ in size.

Standard 5

SP 5/1: I can use mathematical, computational, and/or algorithmic representations of phenomena or design solutions to describe and/or support claims and/or explanations.

SP 5/2: I can apply ratios, rates, percentages, and unit conversions in the context of complicated measurement problems involving quantities with derived or compound units (such as mg/mL, kg/m3, acre-feet, etc.).

Semester 2:

Forensics Quiz:

http://nothingyouneedtoknownows.blogspot.com/2014/02/forensics-quiz.html

In the Forensics Quiz I was able to determine which organs were damaged by using mathematical measures for the entrance wound. With these measurements I was able to eliminate some organs and figure out the cause of death. Then I was able to accurately demonstrate the passage of the bullet, and hypothesized 3 scenarios of how the death could have taken place.

Standard 6

SP 6/1: I can make a quantitative and/or qualitative claim regarding the relationship between dependent and independent variables.

SP 6/2: I can apply scientific ideas, principles, and/or evidence to provide an explanation of phenomena and solve design problems, taking into account possible unanticipated effects.

Projects/Labs:

Semester 1:

Milk in Motion Lab: (SP 6/1)

http://nothingyouneedtoknownows.tumblr.com/post/79140032361/milk-in-motion

pGlo Lab: (SP 6/2)

http://nothingyouneedtoknownows.tumblr.com/post/69851975882/pglo-lab

Semester 2:

Animal Behavior Lab:

http://nothingyouneedtoknownows.blogspot.com/2014/05/animal-behavior-lab.html

In the Animal Behavior Lab, we were able to show the ability to construct explanations from the experiment we designed. The goal of the experiment was to test the pill bug’s behavior in different environments. My partner and I decided to test them according to the moisture and darkness of the environment. We designed the experiments by having 2 chambers, one with a wet filter paper and one chamber with a dry filter paper. We then put 10 Pill Bugs and recorded their activity every 30 seconds. In the second experiment, we replaced the filter papers with a brown paper and a white paper, and also recorded their activity every 30 seconds. We constructed a data table for the the results and we found out that the pill bugs had no preference for color but favored the wet side more The reason is because those environments are most similar to their original environmental conditions and such animal behavior is called a taxis response.

Standard 7

SP 7/1: I can evaluate the claims, evidence, and/or reasoning behind currently accepted explanations or solutions to determine the merits of arguments.

SP 7/2: I can make and defend a claim based on evidence about the natural world or the effectiveness of a design solution that reflects scientific knowledge and student-generated evidence.

Projects/Labs:

Semester 2:

Oral Cancer Project:

https://docs.google.com/document/d/1X3y6zyUxJ2gWPuj-ECteZlnH6m3oUWqbVHc3T8KTm0I/edit

In this project I have evidence from the research that I have and have engaged in arguments by arguing the drug’s viability.

Standard 8

SP 8/1: I can critically read scientific literature adapted for classroom use to determine the central ideas or conclusions and/or to obtain scientific and/or technical information to summarize complex evidence, concepts, processes, or information presented in a text by paraphrasing them in simpler but still accurate terms.

SP 8/2: I can compare, integrate and evaluate sources of information presented in different media or formats (e.g., visually, quantitatively) as well as in words in order to address a scientific question or solve a problem.

SP 8/3: I can communicate scientific and/or technical information or ideas (e.g. about phenomena and/or the process of development and the design and performance of a proposed process or system) in multiple formats (i.e., orally, graphically, textually,mathematically).

Projects/Labs:

Semester 2:

Reflection on the year:

http://nothingyouneedtoknownows.blogspot.com/2014/05/for-sp-8-and-9.html

Standard 9

SP 9/1: I can demonstrate the ability to evaluate my own learning, recognizing areas of strength and weakness, and be able to describe the next steps for improvement.

Projects/Labs:

Semester 2:

Reflection of the year:

http://nothingyouneedtoknownows.blogspot.com/2014/05/for-sp-8-and-9.html

Tuesday, May 27, 2014

For SP 8 and 9

This is to show how I have grown throughout the year as a student.

One of the first things we did in class was to cut out a double helix and follow directions of going through DNA replication. We cut out enzymes and put them where they were supposed to go during DNA replication, such as helicase, RNA primase, DNA polymerase III, DNA polymerase I, and Ligase. The helicase cut the bonds, and the brought in RNA primase to pay out a polar substance so that DNA polymerase III could start laying out the Okazaki fragments. After DNA Polymerase III was finished, we took out the 3 RNA fragments and replaced them with DNA fragments. There were now 2 DNA strands, and ligase came in to bond the Okazaki fragments together again. In this activity, we learned about DNA and its replication process.
Another lab we did was the PGlo Lab. We used the bacteria E. Coli that had been genetically modified to be able to glow in the dark, and were suppressed by an arabinose operon system. Without the arabinose to release the operon sugar, the bacteria cannot glow in the dark. After the operon system is removed and the RNA polymerase is allowed to read the gene and create more of it, then the bacteria can glow.
One of the next activities we did was the Jello Lab. The lab was about proteins and enzymes, and how the enzymes in the fresh pineapple interferes with the proteins that stop gelatin from becoming solid. The reason we could use canned pineapple and have it still work is because the canned pineapple had been heated to such a high temperature that the active site of the enzymes were destroyed. Temperature and pH are the only things that can activate or deactivate an enzyme, or damage it so that it cannot function. Fresh pineapple, however, could still use the enzyme, and did not harden in the Jello.
We also did the yeast lab to demonstrate cellular respiration. We used different temperatures to determine what the best environment for cellular respiration was (hot, room temperature, or cold.) We measured how well it worked by the syringes that were attached onto the top of the test tube. Our result was that the hot plate gave us the most CO2. However, there may have been a few errors in our experiment because the room temperature one gave out less CO2 than the one in ice-- in fact, it didn't give out any CO2, so we concluded that we may have not sealed the test tube tightly enough for the CO2 to go into the syringe.
The last lab we did was the photosynthesis lab. We grew our own radishes, 4 of them (which Mr. Quick accidentally let die) and analyzed what the roots looked like and which ones grew the fastest. Photosynthesis is basically the opposite of cellular respiration, since it changes sunlight, carbon, and water into oxygen and glucose. The plants used the light that we set them in and converted it to carbon and NADPH (electron carriers) and carried out the Calvin Cycle, where glucose is made. The plants growing are proof of photosynthesis and how it works.

Monday, May 26, 2014

Animal Behavior Lab

Title: Animal Behavior Lab

Abstract: In this lab, our task is to find the relationship between animal behavior and environment. We used pill bugs to test animal behavior. We put 10 pill bugs into two petri dishes with different environment, such as dry or wet, to find out what environment they prefer more. The pill bugs can move freely between the petri dishes, so we can conclude which environment the pill bugs prefer from the number of them in each dish. Our lab data shows that in the first setting, most pill bugs stayed in the wet petri dish. In the second setting, we started with 10 pill bugs in white dish and 0 in brown dish, after 5 minutes, 9 remained in white and 1 moved to brown.

Introduction:
1. Behavior is the range of actions and mannerisms made by organisms, systems, or artificial entities in conjunction with themselves or their environment, which includes the other systems or organisms around as well as the (inanimate) physical environment. It is the response of the system or organism to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or covert, and voluntary or involuntary. Although there is some disagreement as to how to precisely define behavior in a biological context, one common interpretation based on a meta-analysis of scientific literature states that "behavior is the internally coordinated responses (actions or inactions) of whole living organisms (individuals or groups) to internal and/or external stimuli"
Behaviors can be either innate or learned.
Behavior can be regarded as any action of an organism that changes its relationship to its environment. Behavior provides outputs from the organism to the environment.
Hypothesis:
If we put the pill bugs into two joined petri dishes with different environment, the pill bugs that can move freely will choose the environment they prefer, thus demonstrating animal behavior. In the first setting, if we put the pill bugs into the dishes, they will move to the wet area because that area is what fits the most with their usual living environment. If we put the pill bugs into the second setting, they should stay at where they are or move freely without purpose, since pill bugs should be blind to colors.

Materials:
10 pill bugs
1 behavior chamber
4 pieces of filter paper (for all 3 parts)
Brushes for moving bugs
Timer/clock
5 ml water
white paper
brown paper

Procedure:
1. Find 10 pill bugs.
2. Place them and a small amount of bedding material in a small petri dish.
3. Observe the pill bugs for 10 minutes.
4. Make one petri dish wet while the other is dry.
5. Observe and record every 30 seconds where the pill bugs are moving.
6. Make one petri dish white and one brown.
7. Repeat step 5.

Result:

Conclusion:
In this lab, we put 10 pill bugs in two petri dishes with different environment. In the first set, the independent variable is wet or dry, the pill bugs moved to the dry dish. In the second set, the pill bugs stayed at where they were (white) rather than move to brown dish. The first set of experiment, we reject our hypothesis. The pill bugs didn't move to the wet area. In the second experiment, we fail to reject our hypothesis, the pill bugs didn't move toward a specific color; rather, they seem indifferent to the colors. So our conclusion is, the pill bugs are colorblind. However, we only did one set of experiment, so the experimental data is very unstable and not very reliable. In addition, the pill bugs seemed very uncomfortable and inactive in the petri dish, so we assumed that they did not accommodate to the new environment in the classroom.

Transpiration Lab

1. Describe the process of transpiration in vascular plants.

Transpiration is the process in which moisture is carried through plants from roots to small pores on the underside of leaves. It changes to vapor and is released to the atmosphere. It also includes a process called guttation, which is the loss of water in liquid form from the uninjured leaf or stem of the plant, principally through water stomata.

2. Describe any experimental controls used in the investigation.

Type of photometer and amount of time for each experiment.

3. What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?

The temperature and light of the surrounding are tested for the rate of transpiration. The rate increased when there temperature is higher, the amount of light is higher and the amount of wind is higher.

4. Did any of the environmental factors (heat, light, or wind) increase the transpiration rate more than the others? Why?

Yes, they all did because the wind blows away water vapor from the plant, causing a higher rate for transpiration.

5.Which species of plants that you tested had the highest transpiration rates? Why do you think different species of plants transpire at different rates?

Coleus has the highest transpiration rate. Different species of plants transpire at different rate because their leaves and pores differ in size.

6.Suppose you coated the leaves of a plant with petroleum jelly. How would the plant's rate of transpiration be affected?

The plant will not be able to evaporate water into the atmosphere since the pores are blocked. Therefore, the rate will decrease.

7. Of what value to a plant is the ability to lose water through transpiration?

It helps cool the plant and transport nutrients.

Cell Respiration Lab

Title: Cell Respiration Lab

Abstract: In this lab, we used yeast, sugar, and salt mixed together to test the factors that affect cellular respiration. Our hypothesis was that temperature influences the rate of cellular respiration and yeast in warm condition would produce more carbon dioxide than those in cold and room temperature. Our result fulfilled the hypothesis that warm conditions produce the most but rejects that the warmer the temperature the most carbon dioxide would be produced. However, during the lab, we could have made some major mistakes that influenced our results.

Introduction: Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. Cellular respiration is a chemical process in which the bonds of food molecules and oxygen molecules are broken and new compounds are ormed that can transport energy to muscles. Cellular respiration also releases the energy needed to maintain body temperature despite ongoing energy transfer to the surrounding environment. Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used as an example to examine the reactions and pathways involved. There are four steps in cellular respiration: Glycolysis, oxidative decarboxylation of pyruvate, citric acid cycle, and oxidative phosphorylation. The equation of cellular respiration is : C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(l) + heat

There are certain circumstances that influence the rate of cellular respiration. Sugar concentration, temperature, pH and other factors are all included.

Hypothesis: If we put the yeast in the ice, then the yeast would breathe slowly and produces less carbon dioxide. If we put the yeast in room temperature, the yeast would breathe faster that those in ice but still not very quickly. If we put the yeast to warm/heating condition, the yeast would breathe very fast and produce the greatest amount of carbon dioxide because cellular respiration requires an optimal temperature.

Materials: yeast, sugar, water, salt, pipets, 3 tuberculin syringe, timer, 3 test tubes, a heater, an ice box.

Procedure:

1. First, we put 30 mL of water into each test tube.

2. Then, we put certain amount of yeast, sugar, and salt into each test tube, make sure sugar is being put into the test tubes at the same time.

3. We put one test tube to ice box, one to the heating plate, and one in room temperature.

4. Insert tuberculin syringe to each test tube.

5. Time the time the yeast takes to breathe and record down the reading on the syringe.

Results:
The heating plate produced the most carbon dioxide, the room temperature one didn't move at all, and the ice cold one also produced some, but not as much carbon dioxide compared to the heating plate.

Conclusion: In this lab, the yeast on the heating plate produced the most amount of carbon dioxide. The yeast in the ice box and in room temperature produced none. The control of this experiment is 1g of yeast, 1 g of sugar and 2g of salt in a test tube. Two possible sources of errors are 1. We didn’t plug in the syringes tight enough so carbon dioxide escaped into air. 2. When producing one of the test tubes, some sugar was spilled so the initial condition could have been different for each test tube. 2 Constants are the time period we wait each time to take the data and the types of tubes, syringes we used. Our result partially rejects partially fails to reject our hypothesis. The yeast in heating condition did produce the most carbon dioxide; however, the other two test tubes produced no carbon dioxide, which rejects our hypothesis that the room temperature one would produce more than the ice one.

Enzyme Lab

Title: Enzymes and Collagen Lab

Abstract: In this lab, we added three different kind of fresh fruits (kiwi, pineapple and mango) to three different petri dishes with jello solution in it and compared the solidification result with the control. We are able to figure out how and why the enzyme in different fruits react differently with collagen in jello.

Introduction: We learned about enzymes and how temperature and pH value affects its function. Enzymes are catalytic proteins. They act as catalysts in the body to help produce and speed up chemical reactions. Every chemical reaction between molecules involves bonds breaking and forming. Enzymes lower the activation energy, which is the initial energy needed to start a chemical reaction. There are special region on the enzymes called the "active site." A substrate that has the same exact shape will fit into that region and react with the enzyme. The substrate will then change its shape as they bind and creates a product in the end. The environment of the enzyme and the substrate can affect the reaction. Temperature and pH value could alter the active site of the enzyme and changes its shape, causing the substrate unable to react with the enzyme.

Hypothesis: If we put in same amount of three different kinds of fresh fruits in the three Petri dishes with the same amount of jello solution in them, not all of them will solidify because the enzymes in the fresh fruits react differently with the collagen in the jello.

Materials:
Four Petri dishes
0.2g fresh cubed kiwi
0.2g fresh cubed pineapple
0.2g fresh cubed mango
39.4ml hot water
39.4ml cold water,
Stirring rod, markers
6.6g jello powder
Measuring cylinder
Beakers.

Procedure:
1. Pour in 6.6g of jello powder into the beaker and mix it with 39.4ml of hot water. Stir the solution with a string rod for about 3 minutes.
2. Add in 39.4 ml of cold water into the solution.
3. Put 0.2g fresh cubed kiwi, 0.2g fresh cubed pineapple and 0.2g fresh cubed mango on three different Petri dishes.
4. Pour in equal amount of jello solution into the three Petri dish with fruits and one without fruits as the control. Label each lid with a marker.
5. Put all the Petri dishes into the fridge until they all solidified.

Results:
In the petri dish with no fruits, the jello solidified the way it was supposed to because it was the control.
In the petri dish with fresh mangos, the jello also solidified and didn't do anything to the mangos, so it proves that the enzymes in the mangos worked well with the collagen in the jello.
In the petri dish with fresh pineapples, the jello solution is still water and the same as how it was in the beginning. The jello did not solidify because the enzymes in the pineapples reacted differently compared to the control.
In the petri dish with fresh kiwi, the jello solution is still the same as it was in the pineapple experiment.

Wednesday, April 23, 2014

Rabbits vs Wolves

The graph shows that as the wolves never increased, the rabbits grew rapidly, until it was nearly 100 times the wolves. However, when there were enough rabbits for the wolves to survive and reproduce, leading to the sharp increase in wolves, the rabbits died off to nearly zero. When there were hardly any rabbits left, the wolves died of hunger, leaving the rabbits to grow again, as can be seen from the end of the experiment.

Sunday, April 20, 2014

Biomes

Biomes and climate

biome: group of similar ecosystems that cover a broad area
major subdivisions of biosphere
two types: terrestrial biomes and aquatic biomes

Climate

average weather in an area over a long period of time
weather is day to day explanation
described in terms of temperature and precipitation
climate of location depends on distance from the equator and distance above sea level

factors also include location relative to ocean or mountain ranges

Temperature

temperature falls from equator to poles
climates can be classified as tropical, temperate, or arctic
temperature falls from lower to higher altitudes

ex. from base of mountain to its peak

ocean also plays an important role in temperature of an area

coastal areas have milder climates because temperature of the ocean changes little from season to season
affects temperature on nearby coasts

Moisture

climates can be classified as arid, semi-arid, semi-humid, or humid
moisture of biome determined by both precipitation and evaporation
evaporation depends on heat from sun
precipitation patterns result from movements of air masses and wind

warm, humid air masses are moved north and south by global air currents
air masses cool and cannot hold as much water
drop moisture as precipitation

air masses are much drier at about 30º north or south latitude

dry climates are found at these latitudes
warn and sunny, which increases evaporation and dryness
dry climates are found near the poles as well
extremely cold air can hold little moisture, so precipitation is low in arctic zones
also have little evaporation because of the cold
cold climates with low precipitation may not be as dry as warm climates with the same amount of precipitation

distance from ocean and mountain ranges also changes precipitation

one side of mountain range near the ocean may receive a lot of precipitation
warm, moist air masses regularly move in from the water
air masses begin to rise up over the mountain range
cools and drops moisture as precipitation
by the time it reaches the other side of the mountain range, they no longer contain moisture
land on the other side of mountain receives little precipitation
land is in the "rain shadow" of the mountain range

Climate and Plant Growth

plants are the major producers in terrestrial biomes
all other terrestrial organisms depend on them directly or indirectly for food
plants need air, warmth, sunlight, water, and nutrients to grow
climate is major factor in affecting number and diversity of plants that can grow
climate determines average temperature and precipitation, length of growing season, and quality of soil

Growing season

period of time each year when it is warm enough for plants to grow
time and length of growing season determines which types of plants can grow in an area

ex. near the poles, the growing season is very short because the temperature may rise above freezing for only a couple of months
slow-growing plants are unable to survive
near the equator, plants can grow year round if they have enough moisture

Soil

plants need soil with nutrients and organic matter
nutrients and organic matter are added to soil when plant litter and dead organisms decompose
decomposition occurs very slowly in cold climates, so soil in cold climates are thin and poor in nutrients
soil is thin and poor in hot, wet climates too because heat and humidity causes rapid decomposition, so little organic matter accumulates in the soil
frequent rains leach nutrients from the soil
thick, rich soil is found in temperate climates and is best for most plants

Biodiversity

refers to number of different species of organisms in a biome
biodiversity greater in wetter and warmer biomes, so generally decreases from equator to poles
rainforest has highest biodiversity of any biome on Earth

Adaptations

plants, animals, and other organisms evolve adaptations to survive through abiotic factors
abiotic factors to which they adapt include

temperature, moisture, growing season, and soil

biomes with dry climates have plants that adapt to aridity, such as special tissues for storing water
biomes with severe cold or dry seasons have plants that maybe become dormant during that season of the year

in dormant plants, cellular activities temporarily slow down so that the plants need less sunlight and water

Thursday, April 17, 2014

Chaparral Biome

Do you want to live somewhere with constant weather, cool climate, and lush trees? Then you probably don't want to live in a chaparral biome. Does it look attractive?

Chaparral Biome

Link: http://education-portal.com/cimages/multimages/16/Chaparral_California.JPG

The chaparral biome is a shrubland, found mostly in California, parts of Mexico, and various parts in the Eurasia continent.

Map of chaparral biome areas (highlighted in green)

Link: http://www.blueplanetbiomes.org/images/chaparral_location_map001.gif

Some abiotic features (physical features) of a chaparral include mild winters, hot and dry summers, infrequent fires, poor soil quality (lacking in nutrients), lots of rocks, and lots of sunlight. Some biotic features (living features, such as plants and animals) include the blue oak, manzanita (a kind of shrub), fairy duster (also a kind of shrub), black-tailed jack rabbits, cactus wrens, grey foxes, mountain lions, desert foxes, spotted skunks, and french brooms (a kind of shrub, not a broom.) For more kinds of abiotic and biotic factors, click here.

Protea plant in the biome

Link: http://www.ri.net/schools/West_Warwick/manateeproject/chaparral/Protea.gif

The producers of the biome are the plants. Some producers include (maybe already have been said above) blue oaks, coyote brush, common sagebrush, fairy duster, french broom, king protea, lebanon cedar, manzanita, mountain mahogany, saltmarsh bird's beak, olive tree, and torrey pine.

The consumers, on the other hand, are the animals in the biome. The consumers include aardwolf, black-tailed jack rabbit, cactus wren, golden jackal, grey fox, isand grey fox, puma, san joachin kit fox, spotted skunk, and wild goats.

There aren't as many decomposers as there are producers and consumers, since fires wipe out everything once in a while, but some decomposers are lichen, vultures, mice, earthworms, and millipedes. Decomposers break down the dead animals and plants.

Humans affect the chaparral biome greatly by going in and building structures such as industries and factories. The biome is changed to suit human needs, but in turn, the organisms are being threatened and endangered. The fires that some organisms need to survive are stopped by the humans, which leaves the organisms with no way to reproduce and pass on their genes.

During the winter, the chaparral climate is mild and moist, but not very rainy. During the summer, contrary to the winter, it is hot and dry. Temperature ranges from 30° to 100° F year round. The chaparral biome only gets around 10-17 inches of rain the whole year, and most of it is from the winter. The plants survive if they have hard or hairy leaves so that they can collect moisture to survive. Because of the hot and dry weather, there are occasionally fires. Many plants are adapted to the fires, and will sprout new plants after a fire to continue living. For more information on climate, click here.

Chaparral during rainy season

Link: http://dpexperience.com/wp-content/uploads/2010/01/CA-Chaparral-Rain-3.jpg

Climate graph of chaparral

Link: http://images.climate-data.org/location/231614/climate-graph.png

Since fires are frequent in the chaparral, many plants and animals have adapted to this event quite nicely. The blue oak tree developed hard tree bark to lessen the severity of the burns from wildfires, and the olive tree has small leaves with protective coating to prevent the evaporation of moisture and to conserve water. The golden jackal has thick fur to insulate it from the cooler chaparral winters, and the island grey fox is smaller than the usual foxes, allowing it to live off of less land and resources.

Black-tailed jackrabbit

Link: http://www.tringa.org/images/9913500129_Black-tailed_Jackrabbit_10-20-2007_2.jpg

There are also some symbiotic relationships in the chaparral. The blue oak tree and common sage brush both produce for other animals, but neither one is dominant, and they don't overpower one another. The red winged blackbird eats the dropped seeds of a torrey pine, but does not harm or benefit the pine in any other way.

Saturday, April 12, 2014

Female Reproductive System (Awkward subject, don't read unless prepared for details)

Collection of organs and other structures located in pelvic region
Functions:

producing eggs, which are female gametes
secreting female sex hormones
receiving sperm during sexual intercourse
supporting the development of a fetus
delivering a baby after birth
breastfeeding a baby after birth

Development before birth

reproductive organs develop into female organs, such as ovaries and uterus, unless an embryo is stimulated by testosterone
most internal female organs have formed by the third month of development
immature ova (eggs), form in ovary before birth
female produces all eggs she will ever make before birth
baby girls are born with reproductive organs present but immature and unable to function
grow very little during childhood
grow rapidly and mature during puberty

Changes of puberty

girls begin puberty a year or two earlier than boys
complete puberty in about four years instead of six
major sex hormone is estrogen rather than testosterone
puberty starts when hypothalamus stimulates pituitary gland to secrete hormones that target ovaries
LH and FSH stimulate ovary to produce estrogen

estrogen promotes growth and other physical changes in females
stimulates development of bones and contributes to adolescent growth spurt in height

changes also involve maturation of organs that are necessary for reproduction
mature reproductive organs are primary sex characteristics
other changes lead to traits that are secondary sex characteristics
menarche (beginning of menstruation) is most significant change (discussed later)

Adolescent growth spurt

females go through growth spurt in height like boys do
growth spurt in girls starts a year or two earlier and ends about three years sooner
do not grow as rapidly during their peak grow rate
average about 10 cm shorter than males on average after growth spurt

Timing of puberty

changes of puberty happens in same order for most females
first observable change is beginning of breast development by about age 10 in the U.S.
the appearance of pubic hair also occurs next, at age 10.5 years, on average
growth spurt in height begins first year of puberty
ovaries and uterus gradually increase in size
menarche occurs usually between age 12 and 13 in U.S. girls
attains adult height by age of 14.5 years
menarche may occur as early as 8 years or as late as 16 years

External female reproductive organs

referred to collectively as vulva
include labia and mons pubis
labia protect vagina and urethra
mons pubis consists of fatty tissue covering the pubic bone, protecting the pubic bone and vulva from injury

Internal female reproductive organs

includes vagina, uterus, fallopian tubes, and ovaries
vagina

tube-like structure about 8-10 cm long
begins at vulva and extends to uterus
has muscular walls lined with mucous membranes
receives sperm during sexual intercourse
provides passageway for baby to leave mother's body during birth

uterus

muscular organ about 7.5 cm long and 5 cm wide
thick lining of tissues known as endometrium
lower, narrower end of uterus is called cervix
cervix is where fetus grows and develops until birth
uterus can expand to accommodate growing baby during pregnancy
muscular contractions of uterus push the baby through cervix during childbirth

fallopian tubes

two of them
7-14 cm long
each tube reaches one of the ovaries
ovary end of tube has fringe-like structure that moves with wavelike motions

ovaries

two small, oval-shaped organs that lie on either side of uterus
egg-producing organs of the female reproductive system
contains hundreds of thousands of immature eggs
each egg is located within a follicle
follicle consists of egg surrounded by special cells that protect egg until puberty then help the egg mature

Breasts

secondary sex characteristics
role in nurturing an infant after birth
each breast contains mammary glands
cells of mammary glands secrete milk, which drains into ducts leading to the nipple

Egg production

a female's ovaries contains all the eggs she will ever produce at birth
eggs do not start to mature until puberty
one egg typically matures each month throughout female's adult years until she reaches middle adulthood

Oogenesis

process of producing eggs in the ovary
eggs are haploid cells, which have half the number of chromosomes of other cells in the body (diploid cells)
must be haploid for sexual reproduction to result in diploid offspring
occurs in several steps that involve different types of cells
begins when oogonium with diploid number of chromosomes undergo mitosis to form primary oocytes
proceeds as primary oocyte undergoes first cell division of mitosis

forms secondary oocytes with haploid number of chromosomes

secondary oocyte undergoes second meiotic cell division to form haploid, if fertilized by sperm
oogenesis begins with oogonia

immature eggs that form in ovaries before birth
diploid cells and equivalent to spermatogonia in males
ovaries contain about seven million oogonia by fifth month of fetal development

oogonia undergoes mitosis, forming cells called primary oocytes

oocytes are also diploid cells

primary oocytes begin first division of meiosis, but do not complete it until long after birth
average female has about 2 million primary oocytes in ovaries
number of oocytes falls as they deteriorate and disappear
by puberty, about 300,000 to 400,000 primary oocytes left in average girl's ovaries

Maturation of a follicle

each month, one follicle starts to mature
primary oocyte in follicle resumes meiosis and divides to form secondary oocyte and polar body (smaller cell)

both are haploid cells

secondary oocyte has most of the cytoplasm from original cell and is larger than polar body
polar body disintegrates and disappears from ovary

Ovulation

release of secondary oocyte by ovary
occurs every 28 days in sexually mature female

may range normally from 24-36 days

each month only one of the ovaries matures a follicle
releases egg
eggs released seem to be at random
after secondary oocyte leaves ovary, it is swept into fallopian tube by the fringe-like ends
cilia line the tube and help oocyte through to the uterus
if secondary oocyte is fertilized by sperm as it is passing through the fallopian tube, it divides to form mature egg and polar body
if not, then it passes into the uterus as an immature egg

Menstrual cycle

ovulation is part of the menstrual cycle
occurs each month in a sexually mature female
menstruation is the process in which blood and other tissues are shed from uterus and leave body through vagina

also called menstrual period, or menses

sometimes divided into two cycles, ovarian cycle and uterine cycle
ovarian cycle includes events that occur in the ovary
uterine cycle includes events that occur in the uterus

two cycles are closely related, so will be talked about as one

Phases of menstrual cycle

cycle begins with menstrual phase

typically lasts from one to four days
when menstruation occurs
arteries that supply endometrium of uterus constrict and break
blood and endometrial tissue detach from inside of uterus and pass from uterus to vagina, then out of the body
if there is an immature egg in the uterus, it passes out of the body with the menstrual flow

ovarian cycle

maturation of follicle, release of an egg, and formation of corpus luteum

uterine cycle

menstruation, development of endometrium, and thickening of endometrium in preparation for an egg

follicular phase

after menstruation
endometrium in uterus begins to build up again
several follicles start maturing in the ovary at the same time
only one follicle will complete maturation
rest will deteriorate and disappear
around day 14 of menstrual cycle, the remaining mature follicle releases oocyte from ovary during ovulation

luteal phase

follows ovulation
endometrium of uterus continues to prepare for fertilized egg
becomes thicker and develops more blood vessels
mature follicle develops into structure called corpus luteum
if egg is fertilized and implants in the endometrium, the endometrium will help nourish it
if not fertilized, the endometrium will break down, leading to menstruation

events of menstrual cycle always occur in the same sequence, but timing may vary
variation may occur from one female to another and from one cycle to the next for a given female
some females have symptoms (bloating, abdominal cramps, and mood swings) before menstruation each month
if symptoms are severe enough to interfere with daily life, condition is called premenstrual syndrome (PMS)

PMS can be helped with medications of lifestyle changes

Role of hormones

same hormones that control female puberty and oogenesis also controls menstrual cycle

LH, estrogen, and FSH

estrogen controls secretion of two pituitary hormones by acting on the hypothalamus

controls pituitary gland
when estrogen levels rise in the blood, it stimulates pituitary gland to secrete more or less LH and FSH

rising levels of hormones initiate a negative feedback that decreases production of hormones
in positive feedback, rising levels of hormones feedback to increase hormone production
estrogen and progesterone provide negative feedback during most of the menstrual cycle
keeps levels more or less constant
estrogen provides positive feedback to hypothalamus and pituitary gland during days 12-14
causes rapid rise in production of estrogen by ovary and leads to ovulation
progesterone

hormone that promotes gestation, or carrying of a fetus
function is to maintain endometrium of uterus

changes in levels of 4 hormones (estrogen, LH, FSH, and progesterone) occurs during menstrual cycle
estrogen secreted by ovaries increases, causing the endometrium of uterus to thicken
FSH stimulates follicles in ovary to mature
the maturing follicles produce estrogen, and level of estrogen rises
when estrogen reaches a certain level, the pituitary gland releases surge of LH

spike in LH stimulates one remaining mature follicle to release oocyte

negative feedback keeps level of FSH, LH, estrogen, and progesterone stable
during ovulation, positive feedback causes increase of FSH, LH, and estrogen
progesterone rises as corpus luteum matures and produces progesterone
negative feedback helps keep levels of other three hormones constant
LH stimulates mature follicle to develop into corpus luteum after oocyte is released
if egg has been fertilized, it will produce a hormone that helps maintain corpus luteum

will continue producing progesterone and maintain endometrium

if it has not been fertilized, the corpus luteum will disappear and stop producing progesterone

endometrium will break down, detach from uterus, and pass out of the body during menstruation

Menopause

menopause occurs when a woman has gone through 12 consecutive months without menstrual period
can no longer reproduce because ovaries can no longer produce eggs
cause of menopause is natural decline in estrogen secretion by ovaries as a woman ages
may take a long time before her body adjusts to drop in estrogen
may experience hot flashes, mood swings, and other symptoms during adjustment period

Friday, April 11, 2014

Endocrine System

System of organs that releases hormones into the blood
Function of endocrine system

endocrine system uses blood vessels to carry chemical information

Organs of the endocrine system (overview)

hormones

chemical messenger molecules that are made by cells in one part of the body and changes cells in another part of the body
regulate many functions that keep you alive
made and secreted by cells in endocrine glands

endocrine glands

ductless organs that secrete hormones directly into blood or fluid surrounding a cell
primary function is to make and secrete hormones
collectively make up endocrine system
other organs, such as stomach, heart, and kidneys, secrete hormones and are considered as part of the endocrine system

exocrine glands

organs that secrete products into ducts (duct glands)
secrete substances, but do not secrete hormones
secrete things like water, mucus, enzymes, and other proteins

Hormones (in detail)

body produces many different hormones
each hormone very specific for target cells
target cell

cell on which hormone has effect

affected by hormones because they have receptor proteins that are specific for hormone
hormones will travel through bloodstream until they find target cells
amino acid based hormones

made of amino acids
can be simple in structure or very large
not fat-soluble and cannot diffuse through plasma membrane of target cell
bind to receptors found on cell membrane

cholesterol based hormones

made of lipids such as phospholipids and cholesterol
hormones are also called steroid hormones
fat soluble and able to diffuse through plasma membrane
found within cell cytosol and nucleus

hormone-like substances

group of signaling molecules derived from certain types of fatty acids and proteins
do not travel around body in blood and are broken down quickly
effects of hormone-like substances are localized in tissue where they are produced
prostaglandins: made from essential fatty acids and produced by most cells in body
have many different effects, like causing constriction or dilation of blood vessels
neuropeptides: signaling peptides found in nervous tissue
many different effects on nerve cells
some have effects on non nerve cells and are called hormones
hormones exit their cell of origin by exocytosis or some kind of membrane transport
cells that respond to hormone may be one of several cell types found in tissues throughout body

Hormone receptors

cells that respond to hormones have two things in common: have receptors that are specific for certain hormones, and receptors are joined with processes that control metabolism of target cell
two ways receptor-bound hormones activate processes within cells
second messenger system

water soluble hormone molecules does not enter cell
binds to membrane bound receptor molecule, triggering change within cell
changes activated by second messenger molecules

direct gene activation

fat soluble hormone diffuses across membrane and binds to receptor within cytosol or nucleus
hormone-receptor complex acts as transcription factor that affects gene expression

Action of glucagon: second messenger system

majority of amino acid based hormones bind to membrane bound receptors
binding of hormone triggers signal transduction pathway

process of molecular changes that turns hormones extracellular signal into intracellular response

activation of receptors by hormones make the intracellular production of second messengers as part of signal transduction pathway
second messenger is a small molecule that starts change inside cell in response to binding of specific signal to receptor protein
glucagon: hormone involved in carbohydrate metabolism

released when glucose level is low
released by pancreas and circulates blood until it binds to glucagon receptor
receptor found in plasma membrane of liver cells
binding of glucagon changes shape of receptor, which activates a G protein
G protein is enzyme that activates next enzyme, activating the next, etc.
end result: enzyme that breaks apart glycogen molecule in liver cell to release glucose molecules in blood
signal transduction pathway, a domino effect in the cell, allows a little bit of hormone to have large effect on cell or tissue

Action of cortisol: direct gene activation

steroid hormones diffuse through cell membrane and bind to receptors in cytosol or nucleus
cortisol

steroid hormone produced by adrenal glands
often called stress hormone because it is involved in body's response to stress
increases blood pressure, blood sugar levels, and has immunosuppressive action
crosses cell membrane and binds to steroid receptor in cytoplasm
enters nucleus of cell and binds to DNA, either activating or deactivating gene transcription

Effects of hormones

effects varies widely
tropic hormones (tropins) regulate production and release of other hormones
other effects

stimulation or inhibition of growth
induction or suppression of programmed cell death (apoptosis)
activation or inhibition of immune system
regulation of metabolism
preparation for new activity
preparation for new phase of life (ex. puberty, caring for offspring, or menopause)
control of reproductive cycle

Hypothalamus

links nervous system to endocrine system by pituitary gland
located below thalamus
found in all mammalian brains
about the size of an almond
complex area of brain, and nerve cells are involved in many different functions
coordinates seasonal and circadian rhythms, complex homeostasis mechanisms, and ANS
circadian rhythm

24 hour cycle in biological processes carried out within organisms

ANS controls activities such as body temperature, hunger, and thirst
hypothalamus must respond to different signals, both outside and outside
connected with many parts of CNS, including brainstem, olfactory bulbs, and cerebral cortex
produces hormones that are stored in pituitary gland

Pituitary gland

about the size of a pea
attached to hypothalamus by thin stalk at base of the brain
secretes hormones that regulate homeostasis
secretes hormones that stimulate other endocrine glands
anterior pituitary (front lobe) makes many important hormones
posterior pituitary (rear lobe) releases two hormones, oxytocin and ADH
hormones transported down the nerve cell's axons to posterior pituitary where they are stored
most hormones are released from anterior pituitary under influence from hormones in hypothalamus
hypothalamus hormones travel to anterior lobe down special capillary system that surrounds pituitary

Thyroid gland

one of the largest endocrine glands in body
butterfly gland found in the neck, wrapped around trachea
hormones released by thyroid control how quickly the body uses energy, makes proteins, and how sensitive the body should be to other hormones
controlled by hypothalamus and pituitary
thyroid hormones generally controls pace of all processes in body
pace is related to metabolism
hyperthyroidism (overactive thyroid) and hypothyroidism (under active thyroid) are common problems of the thyroid gland
thyroxin (T4) and triiodothyronine (T3) regulate rate of metabolism and affect growth of different systems in the body
iodine is very important for making T3 and T4
if not enough iodine, person developed iodine deficiency called goiter

low amounts of T3 and T4 causes pituitary to secrete large amounts of thyroid stimulating hormone (TSH) which causes abnormal growth of thyroid gland
addition of iodine to mass produced foods, like salt, helps reduce the iodine-deficiency in developed countries

also produces the hormone calcitonin, which plays a role in calcium homeostasis

Parathyroid glands

usually located behind the thyroid gland
parathyroid hormone (PTH) maintains blood calcium levels within a narrow range

maintains calcium levels so that nervous and muscular systems can work properly

if blood calcium levels drop below certain point, calcium sensing receptors in parathyroid releases hormone PTH in the blood

PTH increases blood calcium levels by stimulating bone cells to break down bone and release calcium
increases gastrointestinal calcium absorption by activating vitamin D
promotes calcium uptake by kidneys

Pineal gland

melatonin is made in pea-sized pineal gland
located at the base of the brain
production is under control of hypothalamus

receives information from retina about daily pattern of light and darkness

melatonin is involved in sleep cycles, onset of puberty, and immune function
responds to seasonal changes in light

could be reason why getting out of bed on a dull, rainy morning can be so difficult

Pancreas

both exocrine gland and endocrine gland

exocrine gland because it secretes pancreatic juice containing digestive enzymes
endocrine gland because it produced several important hormones

located below and behind stomach
endocrine cells in pancreas are grouped together in areas called inslets of Langerhans

islets produce amino acid-based hormones insulin, glucagon, and somatostatin

insulin

produced by beta cells
causes excess blood glucose to be taken up by liver and muscle cells
stored as glycogen, a polysaccharide

glucagon

produced by alpha cells and stimulates liver cells to break down glycogen into glucose
released into blood

alpha cell

another type of endocrine cell found within the islets of Langerhans

Adrenal glands

located each above the kidneys
separated into two structures

adrenal medulla (center of gland)
adrenal cortex (outer layer)
work as two separate endocrine glands

adrenal medulla

core of adrenal gland
surrounded by adrenal cortex
secretion of hormones from medulla is controlled by sympathetic nervous system
cells of medulla are main source of epinephrine and norepinephrine
hormones are part of fight-or-flight response
boots supply of oxygen and glucose to brain and muscles, suppressing other non-emergency bodily processes

adrenal cortex

site od steroid hormone synthesis
some cells make cortisol, and others make testosterone (or more)
other cells secrete aldosterone, which helps regulate blood pressure
regulated by hormones secreted by pituitary gland and hypothalamus

cortisol (see above)
epinephrine (adrenaline)

fight or flight hormone
released from adrenal medulla when stimulated by sympathetic nervous system
plays central role in short term stress reaction
body's response to threatening, exciting, or environmental stressors, like high noise levels and bright light
binds to multiple receptors when secreted into bloodstream
increases heart rate, dilates pupils, and constricts blood vessels in skin and gut while dilating arterioles in leg muscles
also increases blood sugar levels
begins breakdown of lipids in fat cells
"turns down" non-emergency bodily processes like digestion
depresses the immune system

norepinephrine

similar actions on the body as adrenaline
psychoactive because it affects alertness, helpful for studying

Gonads

ovaries of females and testes of males are gamete producing organs
ovaries are homologous to testes in males
producing gametes is an exocrine action
gonads are endocrine glands that produce steroid sex hormones
sex hormones

responsible for secondary sex characteristics that develop at puberty

puberty

process of physical changes during which the sex organs mature and a person becomes capable of reproducing

gonadotropes

luteinizing hormone (LH) and follicle stimulating hormone (FSH) both secreted by pituitary gland
tropic hormones of the gonads
triggers production of hormones in other glands
secretion of LH and FSH are controlled by gonadotropin-releasing hormone for hypothalamus
pulses are subject to estrogen feedback from gonads

androgens

in males, LH triggers production of sex hormones androgens in testes
main androgen is testosterone
causes increase in skeletal mass and bone density
also responsible for secondary sex characteristics of males, such as facial hair
also produce small amounts of estrogen in the form of estradiol

estrogen and progesterone

rise in LH concentration triggers production of estrogen and progesterone by ovaries
estrogen causes release of an egg from ovaries
progesterone prepares uterus for possible implantation by fertilized egg
placenta is endocrine gland for pregnancy
secrets hormones estrogen, human chorionic gonadatropin, and progesterone
important for maintaining pregnancy

Other hormone-producing tissues and organs

stomach, small intestine, kidneys, and heart
have cells that secrete hormones

Homeostatic imbalance: endocrine system disorders

diseases are common
includes diseases such as diabetes, thyroid disease, and obesity
usually characterized by hyposecretion or hypersecretion of hormones
also inappropriate response to hormone signaling by cells
cancer can occur in endocrine glands (thyroid)
some hormones can signal distant cancer cells to multiply

hyposecretion

production of no hormone or too little of a hormone
can be caused by destruction of hormone-secreting cells

such as Type 1 diabetes, an autoimmune disease that results in destruction of insulin producing beta cells in pancreas

also can be caused by deficiency in nutrient that is important for hormone synthesis
can be treated with hormone-replacement therapies
diabetes insipidus is characterized by excretion of large amounts of dilute urine

caused by inability of kidney to concentrate urine because of lack of ADH
insensitivity of kidneys to hormone
blood glucose levels are not affected in diabetes insipidus

growth hormone deficiency

caused by lack of GH production in pituitary gland
affects bone growth development
have low bone density and small stature, called pituitary dwarfism
treated by growth hormone replacement

hypothyroidism

not enough thyroid hormones are made
autoimmune disease where body's antibodies attack cells of thyroid and destroy it
plays important part in brain development during fetal growth
hypothyroidism in child is major cause of physical and mental growth impairment in developing countries
iodine deficiency is most common cause of preventable mental retardation and brain damage in the world

hypersecretion

body produces too much of a hormone
hormone can be hypersecreted if gland develops a tumor and grows out of control
hyperthyroidism

result of excess thyroid hormone production
causes overactive metabolism
increased speed of all body's processes
most common cause of goiter in developed world

hypersecretion of growth hormone causes acromegaly

common cause of acromegaly is benign tumor of pituitary glands that releases too much GH
also caused by overproduction of hypothalamus hormone GHRH
most commonly affects middle aged adults and can result in illness and premature death
symptoms: enlarged hands and feet, protruding brow and chin, and enlarged internal organs
disease is hard to diagnose in early stages
frequently missed for many years due to slow progression
if pituitary produced too much GH during childhood, the person will be taller than normal
called pituitary gigantism, which is very rare, and some of the tallest people on record have this condition

Hormone insensitivity: Type 2 diabetes

sometimes, the body makes enough hormones, but body cells do not respond
can be due to missing or defective hormone receptors
body cells became resistant to normal concentration of hormone, and don't respond to it
Type 2 diabetes

characterized by hyperglycemia
body cells that don't respond to normal amounts of insulin
resulting inability of pancreas to produce enough insulin
high amounts of free fatty acids and glucose in blood
high plasma levels of insulin and glucose lead to metabolic syndrome and type 2 diabetes
type 2 diabetes can be controlled by improving diet, increasing levels of activity, and sometimes medication

gestational diabetes

form of diabetes that affects pregnant women
no known single cause
hormones produced during pregnancy reduce ability of cells in pregnant woman's body to respond to insulin
results in high blood glucose concentrations

Hormones as medicines

hormone-replacement therapy
most commonly prescribed hormones are estrogens and synthetic progesterone
progestin used to prolong pregnancy in women to have experienced miscarriage due to premature drop in progesterone levels

Epinephrine

anti inflammatory effect on immune system

used to treat anaphylaxis
sudden and severe allergic reaction that involved entire body
histamine causes blood vessels to dilate
lowers blood pressure, and fluid leaks from bloodstream into tissues
can cause difficulty breathing

Anabolic androgenic steroids

synthetic androgens have many medical uses

used to stimulate bone growth and appetite
induce puberty in boys
treat muscle-wasting conditions in patients

promotes protein synthesis and growth of muscle tissue and other tissues
blocks effects of stress hormone cortisol, so breakdown of muscle is greatly reduced

Anabolic steroid abuse

used in sport and bodybuilding to increase muscle size and strength to gain competitive edge or to assist in recovery from injury
steroids used to gain competitive advantage are forbidden by rules in many sports
hearth risks can be produced by long term use or excessive doses of anabolic steroids
most side effects are dose dependent

most common side effects: increase in bad cholesterol, and decrease in good cholesterol
acne is common among anabolic steroid users
more testosterone is produced, which leads to more oil being produced

teenage boys who take anabolic steroids are more likely to be involved in sports that depend on weight and shape
have higher rates of disordered eating, drug abuse, and have poorer attitude towards health
steroids may prematurely stop lengthening of bones (stunted growth)
accelerated bone maturation, increased acne outbreaks, and premature sexual development

Wednesday, April 9, 2014

Nervous System

Nervous system is complex network of nervous tissue that sends electrical and chemical signals

includes central nervous system (CNS) and peripheral nervous system (PNS) together
CNS made of brain and spinal cord
PNS made of nervous tissue that lies outside of CNS

nerves in the legs, arms, hands, feet, and organs of the body

nervous system mediates communication between different parts of body

Nerve cells

two main types of nerve cells in nervous tissue
neuron

"conducting" cell that transmits electrical signals, and structural unit of nervous system

glial cell

provides a support system for neurons and are involved in synapse formation
astrocytes: type of glial cell in brain, important for maturation of neurons and involved in repairing damaged nervous tissue

neurons and glial cells make up most of the brain, spinal cord, and nerves that branch out to every part of the body
both neurons and glial cells are referred to as nerve cells

Structure of a neuron

neuron has a special shape

allows it to pass electrical signal to another neuron and other cells

electric signals move rapidly along neurons so that they can pass "messages" from one part of the body to another

called nerve impulses

neurons made of cell body (soma), dendrites, and axon
cell body contains nucleus and other organelles
dendrites extend from cell body and receive nerve impulses from another cell
cell body collects information from dendrites and passes it to an axon
axon is a long, membrane-bound extension of the cell body

passes nerve impulse onto next cell

end of axon is called axon terminal

point where the neuron communicates with the next cell

summary

dendrites receive information
cell body gathers it
axons pass information to another cell

myelin sheath

axons of man neurons are covered with this insulating phospholipid layer
speeds up transmission of a nerve impulse
outgrowth of glial cells

Schwann cells

type of glial cell
flat and thin, containing a nucleus and other organelles

oligodendrocytes

supply myelin to those of the brain or spinal cord
myelinated neurons are white, and makes up "white matter" in brain

myelin is not continuous along axon
regularly spaced gaps are called Nodes of Ranvier

only points at which ions can move across axon membrane through ion channels
nodes act to strengthen nerve impulse by concentrating the flow of ions at nodes of Ranvier along axon

neurons are specialized for passing of cell signals
many different shapes and sizes
synapse: specialized junction at which neurons communicate with each other
a neuron can have one or many axons

longest axon of human motor neuron can be over a meter long, reaching rom base of spine to toes

sensory neurons have axons that run over 1.5 meters in adults

Ion channels and nerve impulses

ion transport proteins have special role in nervous systems

voltage-gated ion channels and ion pumps are essential for forming nerve impulse

uses energy to build and maintain a concentration gradient between extracellular fluid and cell's cytosol

concentration gradient results in net negative charge on inside of membrane and a positive charge on the outside.

ion channels and ion pumps only allow certain ions through the cell membrane

potassium channels will only allow potassium ions through
sodium-potassium pumps acts only on sodium and potassium ions

all cells have electrical charge, due to concentration gradient of ions that exist across membrane
number of positively charged ions outside of membrane is greater that number of positively charged ions in cytosol
this charge difference causes voltage difference across membrane
voltage: electrical potential energy caused by separation of opposite charges

across the membrane in this case

voltage across membrane is called membrane potential

basis of conduction of nerve impulses along cell membrane of neurons

ions that are important in formation of nerve impulse includes sodium (Na+) and potassium (K+)

Resting potential

when a neuron is not conducting nerve impulse, it is at rest
resting potential: resting state of neuron, during which neuron has an overall negative charge
in neurons resting potential is approximately -70 mV
reasons for overall negative charge:

sodium potassium pump removes Na+ ions from cell by active transport
net negative charge inside cell is because of higher concentration of Na+ ions outside of cell than inside of cell
most cells have potassium-selective ion channel proteins that remain open all the time
K+ ions move down concentration gradient (passive) through potassium channels and out of cell
results in a build-up of excess positive charge outside the cell
number of large, negatively charged molecules (proteins) inside the cell

Action potential

electric charge that travels along membrane of a neuron
generated when neuron's membrane potential is changed by chemical signals from nearby cell
cell membrane potential changes quickly from negative to positive as sodium ions flow in and potassium ions flow out of cell through ion channels
cell becomes depolarized
action potential works on all or nothing basis
membrane potential has to reach a certain level of depolarization (threshold), or an action potential will not start

threshold varies (~15 mV)

if membrane depolarization does not reach threshold, then an action potential will not happen
first channels to open are sodium-ion channels, allowing sodium ions to enter the cell
increases positive charge in cell
starts up action potential
potassium-ion channels close, and sodium-potassium pump restores resting potential of -70 mV
action potential will move down axon towards synapse like a wave
in myelinated neuron, ion flows occur only at nodes of Ranvier
action potential signal "jumps" along axon membrane, from node to node, rather than all along the membrane
due to clustering of Na+ and K+ ion channels at Nodes of Ranvier

Types of neurons

neurons are specialized for processing and transmission of cellular signals
can be classified by structure of function
strucural classification is based on number of dendrites and axons that a cell has
functional classification is based on direction in which nerve impulse is moving in relation to CNS
sensory neurons

carry signals from tissues and organs to CNS
are sometimes called afferent neurons
typically have long dendrite and short axon
found in reflex arcs
involved in several forms of involuntary behavior, like pain avoidance (reflex)

motor neurons

carry signals from CNs to muscles and glands
are sometimes called efferent neurons
long axon and short dendrites

interneurons

connect sensory and motor neurons in pathways that go through CNS
called association or relay neurons
found only in CNS where they connect neuron to neuron

Communication between neurons

communicate with each other at specialized junctions

called synapses

also found at junctions between neurons and other cells
two types of synapses
chemical synapses: uses chemical signaling molecules as messengers
electrical synapses: uses ions as messengers
synaptic cleft

gap between axon terminal and receiving cell

transmitting cell is called presynaptic neuron
receiving cell called postsynaptic cell

or, if it is another neuron, postsynaptic neuron

brain has a large amount of synapses
approx. one trillion neurons (including glial cells) have an average of 7,000 synaptic connections to other neurons
brain of a three year old child has about 10 quadrillion synapses

number declines with age
adult has between 1-5 quadrillion synapses

Neurotransmitter release

when action potential reaches axon terminal, it causes neurotransmitter vesicles to fuse with terminal membrane
neurotransmitter is released into synaptic cleft
neurotransmitter

chemical message used to relay electrical signals between neuron and another cell
neurotransmitter molecules are made inside of presynaptic neuron and stores in vesicles at axon terminal
some neurons only make one type of neurotransmitter, but most neurons make two or more kinds of neurotransmitters

when action potential reaches axon terminal, neurotransmitter vesicles are caused to fuse with terminal membrane
neurotransmitter is released into synaptic cleft
then diffuse across synaptic cleft and bind to receptor proteins on membrane of postsynaptic cell

Neurotransmitter action

neurotransmitters can have excitatory or inhibitory effect on postsynaptic cell
excitatory neurotransmitter

initiates action potential

inhibitory neurotransmitter

prevents an action potential from starting

glutamate is more common excitatory transmitter in body
GABA and glycine are inhibitory neurotransmitters
release of excitatory neurotransmitter causes inflow of positively charged sodium ions into postsynaptic neuron
inflow of positive charge causes depolarization of membrane
depolarization spreads to rest of postsynaptic neuron
effect of neurotransmitter also depends on receptor it binds to

a single neurotransmitter may be excitatory to receiving neuron, or it may inhibit an impulse by causing a change in membrane potential

synapses can also be excitatory or inhibitory and will either increase or decrease activity in target neuron

depends on opening or closing of ion channels

neurotransmitter receptors can be gated ion channels that open or close through neurotransmitter binding
can also be protein-linked receptors

not ion channels
cause a signal transduction that involves enzymes and other molecules in postsynaptic cell

Neurotransmitter reuptake

reuptake

removal of neurotransmitter from synapse by pre-synaptic neuron
happens after neurotransmitter has transmitted nerve impulse
without reuptake, neurotransmitter molecules might continue to inhibit or stimulate and action potential

reuptake is carried out by transporter proteins that bind to released transmitter and actively transports it across plasma membrane into pre-synaptic neuron
reuptake is target of some types of medicine
is a form of recycling because neuron takes back released neurotransmitter for later use
another way neurotransmitter is removed from a synapse: digestion of enzyme

Neurotransmitters and diseases

Parkinson's disease

deficiency of neurotransmitter dopamine
progressive dead of brain cells give this deficit, causing tremors and a stiff, unstable posture
L-dopa is given as a medicine that eases symptoms of Parkinson's disease
acts as a substitute neurotransmitter, but cannot reverse disease

tetanus

Clostridium tetani produces neurotoxin
bacteria usually gets into body through injury cause by object contaminated with C. tetani spores
blocks release of neurotransmitter GABA

GABA causes skeletal muscles to relax after contraction

when release of GABA is blocked, muscle tissue does not relax and remains contracted
can be fatal when it affects muscles used in breathing
tetanus is treatable and can be prevented with vaccination

botulism

caused by Clostridium botulinum
produces toxin that is occasionally found in preserved foods that were improperly sterilized
butolin toxin blocks release of excitatory neurotransmitter acetylcholine
blockage of acetylcholine causes progressive relaxation of muscles because they are unable to contract
paralysis of muscles used for breathing can be fatal unless treated with a respirator

Central nervous system

includes the brain and the spinal cord
largest part of the nervous system
brain is central control of nervous system
spinal cord carries nerve impulse from brain to body and from body to brain
together with PNS, it controls every activity in the body
brain is protected by skull
spinal cord protected by vertebrae

The brain

most complex organ in the body
contains about 100 billion neurons

can be connected to tens of thousands of other neurons in the brain

source of what makes us human: conscious mind
mind is set of cognitive processes related to perception, interpretation, imagination, memories, and language
regulates processes related to homeostasis (respiration and heartbeat, etc)
average human adult brain weights 1-1.5 kg
brain uses about 20-25% of total energy used by adult body

in infants, uses about 60% of total energy

cerebrum

controls conscious functions

problem-solving and speech

midbrain and stem are more involved with unconscious (automatic) functions

breathing, heartbeat, and temperature regulation

cerebrum involved in coordination and control of body movement

Cerebrum (in detail)

what most people would think of as the "brain"
lies on top of the brainstem
made of two cerebral hemispheres

connected to each other at corpus callosum
callosum is a wide, flat bundle of axons found deep inside the brain
mammals have the largest and most well-developed cerebrum of all species

each hemisphere can be divided into four parts (lobes)
frontal lobe, parietal lobe, temporal lobe, and occipital lobe
both hemispheres look identical

functional differences between them

each cerebral hemisphere receives sensory information

also controls muscle movements of opposite side of body

cerebral cortex

highly-folded outer layer of cerebrum
2-4mm thick
lobes that make up cerebral cortex are named after skull bones that cover those areas of brain
many folds in cortex allows large surface area of brain to fit into skull
controls higher functions: consciousness, reasoning, emotions, and language
also controls sensory functions: touch, taste, smell, and responses to external stimuli

white matter

in the cerebrum and found below the cerebral cortex
made up of myelinated axons that act as "cables" to link up certain parts of the right and left hemispheres

Diencephalon

region of brain that includes structures such as thalamus, hypothalamus, and portion of pituitary gland
thalamus believed to "translate" sensory signals for cerebral cortex

also plays important role in regulating states of sleep and wakefulness

hypothalamus controls certain metabolic processes and other autonomic activities

body temperature, hunger, thirst, and circadian cycles
makes and releases neurotransmitters that control action of pituitary gland

thalamus, hypothalamus, and hippocampus together are called limbic system

"emotional center" of brain

Brain stem

sometimes called the "lower brain"
lower part of brain that joined to the spinal cord
three parts: midbrain, pons, and medulla oblongata
midbrain

more involved with unconscious, autonomic functions
deals with several types of sensory information (sound and sight)
"translates" sensory information to be sent to forebrain
helps coordinate large body movements like walking and running

pons

relays messages to different parts of the brain (cerebrum and cerebellum)
helps regulate breathing
might have role in dreaming

medulla oblongata

also called medulla
shares some function of pons
controls several homeostasis functions such as breathing, heart and blood vessel activity, swallowing, and digestion

brain stem is information highway
all information coming from body to brain and information from cerebrum to body go through brain stem
sensory pathways for pain, temperature, touch, and pressure sensation go upward to cerebrum
motor pathways for movement and other body processes go downward to spinal cord
most axons in motor pathway cross from one side of CNS to the other, passing through medulla oblongata
right side of brain controls movement of left side of body
left side of brain controls movement of right side of body

Cerebellum

found just below occipital lobe of cerebrum
plays important role in coordination and control of body movements
many nerve pathways link cerebellum with motor neurons

neurons that send information to muscles, causing them to move
group of nerves that provides information on the position of body in space

cerebellum processes information from both pathways
uses feedback on body position to fine tune body movements

hand-eye coordination is a fine-tuned body movement

if cerebellum is damaged, there will be no paralysis, but fine movement of the body will be negatively affected

Spinal cord

thin, tubular bundle of nervous tissue
extends from medulla oblongata and continues to lower back
ends in group of fibrous extensions
protected by spinal vertebrae
main function of spinal cord is an information superhighway that links sensory messages from body to brain
outer cortex of cord contains white matter
central region, grey matter, is made up of un-myelinated neurons

Peripheral nervous system

consists of nervous tissue that lies outside the central nervous system
nervous tissue of PNS serves limbs and organs
CNS interacts with peripheral nervous system through twelve pairs of cranial nerves
connects brain to areas of head and neck and
31 pairs of spinal nerves connect the spinal cord to rest of the body (such as internal organs, arms, and legs
nerve: an enclosed, cable-like bundle of axons
peripheral nervous system is not protected by bone, making it more vulnerable to toxins and injuries
spinal nerves originate from spinal cord
control functions of the rest of the body
each spinal nerve has a dorsal root and ventral root
dorsal root

nerve highway that carries sensory information from sensory receptors in body to CNS

ventral root

contains axons of motor neurons which carry information away from CNS to muscles and glands of body

dorsal and ventral root "highways" are parts of two subdivisions of PNS
sensory division

carries sensory information from sensory receptors in body to CNS
keeps CNS constantly updated on events happening inside and outside the body

motor division

also called efferent division
carries nerve impulses from CNS to muscles, glands, and organs of the body
nerve impulses causes muscles to contract and glands to secrete chemical signals

Somatic and autonomic nervous systems

motor division of PNS is divided into somatic nervous system and autonomic nervous system
somatic nervous system

part of PNS that is associated with conscious control of body through movement of skeletal muscles
also through perception of external stimuli through senses
includes all neurons connected with muscles, skin, and sense organs
made up of sensory nerves that receive sensory information from external environment
motor nerves responsible for muscle contraction
sensory, interneurons, and motor neurons are found in reflex arc
reflex: automatic (involuntary) action caused by defined stimulus and carried out through reflex arc
ex: person stepping on sharp object would start reflex action through creation of stimulus

stimulus would be passed along sensory neurons to spinal cord
usually process by interneuron to create immediate response by initiating a motor response by pulling the food away from the object
reflexive action would occur as pain sensation is arriving in brain

autonomic nervous system (ANS)

part of PNS that maintains homeostasis in body
body carries out these activities without conscious control
sometimes also called involuntary nervous system
ANS made up of sensory and motor neurons that send messages to and from internal organs
neurons form reflex arcs that pass through medulla oblongata
low level brain functions will continue to function, called vegetative state

ANS subdivisions
sympathetic division

stimulates body systems during emergency situations
gets body ready for "fight or flight"

parasympathetic division

controls non-emergency functions like digestion

Sense organs and sensory perception

senses are body's means of making sense of information your nervous system receives
enables you to adapt to change in environment and survive
sensory division is organized into developed sense organs

groups of tissues that work together in responding to a specific kind of physical stimulus

sense organs correspond to defined region within the brain where nerve signals are received and interpreted
sense organs include: eyes, ears, nose, mouth, and skin
all have sensory receptors that are specific for certain stimuli
chemoreceptors respond to stimuli
mechanoreceptors respond to mechanical stress or strain
thermoreceptors respond to temperature changes
photoreceptors respond to variations in light
baroreceptors respond to pressure
specific areas of brain interpret information from each sense organ

generally agreed that humans have at least seven different senses
sight, sound, taste, smell, touch, balance, and body awareness

Sight

sight (vision) describes ability of brain and eye to detect wavelengths of electromagnetic radiation

interprets image as "sight"

different receptors are responsible for perception of color or brightness
photoreceptors are found in retina
structure of eye focuses completely on the task of focusing light onto retina

light-sensitive inner layer of eye

light passes through clear protective layer called cornea
light then passes through the pupil, and into the interior of the eye

pupil is opening to the iris

then travels to lens

transparent, biconvex structure that helps to focus light on retina

muscles attached to lens change the shape of the lens to bend light rays so that they focus on retina
light hitting retina causes chemical changes in photosensitive cells of retina
retina has two forms of photosensitive cells: rods and cones
rod cells

highly sensitive to light, letting them respond in dim light and dark conditions
cannot detect color
the darker conditions become, the less color things seem to have

cone cells

responds to different wavelengths of bright light to initiate nerve impulse
responsible for sharpness of images
do not respond well in poor light conditions
three different kinds of cone cells
contains pigment that absorbs energy from different wavelengths of light to initiate nerve impulse
activation of visual pigments opens ion channels on membrane of cone or rod cell
leads to action potential, carried by millions of neuron axons, that make up optic nerve to visual centers of the brain
brain integrates nerve impulses from cone cells and perceives world in all the colors of the visual spectrum

Hearing

sense of sound perception that results from movement of tiny hair fibers in inner ear
hairs detect motion of membrane which vibrates in response to changes in air pressure
can also be detected as vibrations that are conducted through body
sound wave frequencies that are too low or too high are detected as vibrations
pinna

folds of cartilage surrounding outer ear canal

sound waves gathered by pinna and channeled down auditory canal

tube-shaped opening of ear that ends at tympanic membrane, or eardrum

sound waves traveling through ear canal hits eardrum, causing it to vibrate
wave information travels across middle air cavity to the three, tiny delicate bones: hammer, anvil and stirrup
transfers eardrum vibrations to another membrane called oval window

separates middle ear from inner ear
inner ear contains cochlea

cochlea

coiled tube that is filled with watery liquid
moves in response to vibrations coming from middle ear through oval window
hair cells (mechanoreceptors) bend, releasing neurotransmitter
causes and action potential in neurons of auditory nerve
travels along auditory nerve to structures in brainstem
loud noise can kill hair cells
common cause of partial hearing loss
hairs never grow back once they are destroyed

Balance and the ears

ears are also in charge of sense of balance
semicircular canals are three fluid-filled, interconnected tubes found inside each ear
canal filled with fluid called endolymph

cilia lines each canal

movement of head and body cause endolymph in canals to move about
hair cells sense strength and direction of fluid's movement, and sends electrical signals to cerebellum

interprets information and responds to help keep body's sense of balance

when sense of balance is interrupted, it causes dizziness and nausea
balance can be upset by inner ear infection, or a number of other medical conditions
can be temporarily disturbed by rapid and repetitive movement

Taste

four types of taste receptors on tongue
taste stimuli sends information to different region of the brain
detects sweet, salt, sour, and bitter
umami, a fifth receptor, was confirmed in 2000

detects amino acid glutamate, which causes a savory, "meaty" flavor in foods

chemoreceptors of mouth are taste cells found in bundles called taste buds
most are embedded within tiny papillae, or bumps, that cover the tongue
each receptor has a different way of detecting certain compounds and starting action potential, alerting the brain
compounds bind to receptors in taste cells and stimulate neurons in taste buds
action potential moves along facial nerves to thalamus, then to taste center of cerebral cortex for interpretation by the brain
tongue can feel temperature, coolness (minty), spiciness, and fattiness (greasy)

Smell

other "chemical" sense
chemoreceptors of smell are called olfactory receptors
40 million olfactory receptor neurons line the nasal passages
different molecules bind to and excite specific olfactory receptors
combination of excitatory signals makes up what we identify as "smell"
signals from receptors travel along nerves to olfactory bulb in the brain

moves to smell center in frontal lobe of cerebral cortex
olfactory neurons in nose differ fro most other neurons
die and regenerate on regular basis

sense of taste and smell are closely linked
nasal cavity connects to mouth at back of throat
olfactory receptors and taste receptors both contribute to the flavor of food

Touch, pressure, and pain

sense of pressure perception, generally felt in skin
variety of pressure receptors that respond to variations in pressure and tension
mechanoreceptors most numerous on tongue, lips, face, palms, and soles of feet
nociceptors

respond to potentially damaging stimuli
mostly found in external parts of body: skin, cornea, and mucous membranes
also found in muscles, joints, and some internal organs
classified according to stimuli to which they respond

thermal, mechanical, or chemical

thermal receptors: activated by potentially harmful heat or cold
mechanical receptors: respond to excess pressure, squeezing, or bending

Drugs and the nervous system

drugs

andy chemical or biological substance that affects body's structure of functions
can be used to treat many illnesses or disorders

medicine

drug that is taken to cure or reduce symptoms of an illness

drugs can be abused for the effects they have on the CNS
psychoactive drug

substance that affects CNS by altering cognitive function
results in change of how a person feels, thinks, perceives, and acts
coffee or tea contains psychoactive drug caffeine
psychoactive drugs affect how neurons communicate with each other
can alter neurotransmission by blocking receptor protein
some effects are beneficial, like taking a prescribed painkiller to ease pain of broken bone
some are harmful, like if a person takes a strong painkiller long after their broken bone

Drug abuse

repeated use of drug without advice or guidance of medical professional

used for reasons other than what drug was originally intended for
if a person uses the drug continuously, they may find they cannot function normally without the drug
called physical dependence
psychological dependence: emotionally or mentally needing a drug to be able to function normally
eventually need to take larger doses of drug to get desired effect, known as building a tolerance to the drug

person who is abusing a drug may eventually lose control of drug-taking behavior, and resort to stealing and lying to get money or drugs

addiction
drug addict's life revolves around getting more drugs to feed their habit

some people can lead to drug overdose if they keep on increasing the dose

generally considered harmful and may lead to death

drug dependence and addiction are caused by changes in the way neurons in the CNS send and receive neurotransmitters
dependency and addiction are treated as brain disorders by medical professionals
stimulants

cocaine, nicotine, amphetamine
increases activity of sympathetic nervous system, central nervous system, or both
generally increase heart rate, blood pressure, and increase sense of alertness
caffeine are used medicinally to increase or maintain alertness, and to counteract fatigue
high doses can be fatal

hypnotics

depressants
alcohol, codeine, barbiturates, and benzodiazepines
decrease activity of central nervous system
slows down brain function and gives drowsy or calm feeling
taking too much can lead to slow breathing and slow heart rates, and can lead to death
depressants increases activity of inhibitory neurotransmitters GABA
promotes sleep
slows down brain function and causes drowsy and calm feeling
generally prescribed to relieve symptoms of anxiety or insomnia

hallucinogens

also known as psychedelic drugs
do not increase or decrease a certain feeling or emotion
induce experiences, such as sensory distortions and "out of body experiences"
different from those of ordinary consciousness
often called trance-like states
has been linked to potential for brain damage

drugs that increase activity on particular neurotransmitters are called agonists
drugs that reduce neurotransmitter activity are called antagonists

work by interfering withs synthesis
also blocks postsynaptic receptors so neurotransmitters cannot bind to them

different drugs affect different parts of the brain

How addiction happens

neurobiological theory of addiction proposes that certain chemical pathways are changed in the brain of an addicted person
most abused drugs affect brain structures in the limbic system

called the brain rewards system
provides feeling of pleasure that motivates person to perform certain activities over and over again
dopamine released at synapses by neurons when person has a pleasurable experience
this mechanisms has evolved to ensure survival of organisms

some drugs (cocaine, nicotine, amphetamines, and alcohol) increase the amount of dopamine in the limbic structure

tricks body into thinking that drug is good and important for survival

drugs that affect brain reward system are highly addictive

nicotine is highly addictive

many psychoactive substances are abused for their mood and perception altering effects
drugs that have no medical uses and high potential for abuse are usually illegal
not all drugs are physically addictive