I decided to go off on my own and find another interesting odor fact. Above is a link to an article that introduces a new app that is soon to hit the market. Think smell-o-vision in reverse. This app uses technology like that found in the article about UCSB’s mechanical nose. The technology is able to “take the sense of smell and taste and digitized them”, explains creator Sam Khamis. When finished, this app (actually a device that will plug into your phone) will use 4,000 sensors to tell warn you when you have bad breath! At least it’s better than the person sitting next to you!! Khamis does warn, though, this will not be a device that emits smell, only detects.
Action Potential Fun Facts!!!
-a rapid, temporary change in membrane potential
-“all or nothing”
-will fire at threshold (-55mV)
-myelin sheath/Schwann Cells coat the axon/insulate so action potential jumps quickly along
-positive feedback
-occurs in milliseconds
-frequency is better than size
-depolarization due to Na+ influx
-repolarization due to K+ outflux
-arrival at axon terminal triggers Ca++ entry thus releasing neurotransmitters
-chain reaction from other dendrites processed at cell body “decided” to be sent out
-works down axon to send signals to neighboring dendrites; to cause an action
Simplified Steps:
1. Signal Received
2. Voltage Gated Na+ Channels open upon -55mV, Na+ enters cell, becomes more +
3. Voltage Gated K+ Channels open upon +40mV, K+ leaves cell, becomes more –
4. Undershoot/hyperpolarization (more negative than resting potential)/Refractory Period
(Prevents action potential from reversing)
*Maintenance of Resting Potential: Na/K Pumps, “Leaky K+” Channels, Organic Proteins.
*Cl- fights between its concentration & electrochemical gradient for entrance into cell, “regulator”.
Quick, easy video description of the above:
If I were to form a question about Action Potentials, I would ask: Many diseases interfere with action potentials in different ways, how can action potentials be interrupted to cause dysfunction?
Diffusion – Flick’s Law of diffusion explains that there are 5 different parameters for diffusion of a gas: solubility of the gas, temperature, surface area, differences in partial pressures, and finally the thickness of the barrier to diffusion.
Gills in fish are so efficient in breathing under water because they have such a large surface area, allowing O2 to diffuse across the thin epithelium. They also have a counter current exchange system which causes water and blood to flow in opposite directions.
SO, we know that in humans, CO2 and O2 are transferred around the body via the blood (veins, arteries, etc.). O2 can easily bind to blood because blood has such a high oxygen carrying capacity. When the binding of successive O2 molecules to a subunit of hemoglobin molecule occurs, this creates a conformational change – the protein can now more easily bind to O2! THIS creates that S-shaped curve on a graph.
The role of Carbonic Anhydrase – When CO2 enters a red blood cell, carbonic anhydrase turns it into an acid, which breaks it down into a bicarbonate ion and proton (creating a partial pressure gradient, allowing CO2 to enter RBCs). – The protons produced then bind to deoxygenated hemoglobin.
This video is from like 1982, but it was pretty helpful! 🙂
This goes really into depth, but it has some useful info
What would Bryan think are the most important things from this section?
I think that Bryan will want us to for sure understand the closed circulatory system. SO… in the closed circulatory system, blood is flowing throughout the body continuously. It flows through the body under pressure that is generated by the heart. The reason that blood can maintain a high flow rate in a close circulatory system is because the blood is confined to vessels. An interesting fact about the closed circulatory system is that blood can be directed where you need it in the body. Vertebrates have a closed circulatory system. Types of blood vessels: arteries- thick walled, take blood away from the heart. Capillaries- walls are just one cell thick, this allows for diffusion of gasses. Veins- these return blood to the heart.
Since capillaries are thin walled, and the pressure of the system is pretty high, fluid steadily leaks from blood vessels to the surrounding space. This fluid is called interstitial fluid. It resembles plasma in it’s electrolyte composition. A lot of this fluid is taken back in by the veins.
The rest of the fluid is collected by the lymphatic system. Once this happens it is then called lymph.
How does the heart work? See picture
High blood pressure=Hypertension
What do I think are the most important things from this section?
I think that the most important things in this section are how a heart works and also memorizing the flow of blood through the heart. I am uploading a picture that I drew along with this so that you can see. It helped me study so maybe it will be helpful for you guys as well.
How can I explain this stuff in an easier way?
All of this stuff is pretty straight forward, I think that it is way easier to memorize on paper how a heart works than it is to apply it in real life. The one thing that will be helpful to remember is that although on diagrams it looks like the blood flows in the superior vena cava through all of the chambers then out the pulmonary artery to the lungs then back in through the pulmonary vein, it is actually happening simultaneously. So blood is flowing in through the Superior vena cava and in through the pulmonary vein at the same time.
What am I still confused about?
In this section I am not really confused about anything. The only thing that maybe I would like to have better explained to me is the homeostatic control of blood pressure.
Question:
We know that backflow thought a valve reduces the efficiency of a heart. But what if both the semi-lunar valves (pulmonary and aortic) were “leaky”, or had backflow. Would the result be just a “double murmur” or would the consequences be direr?
I cant figure out how to add the image of the heart that I drew into this comment, so if you are interested in seeing that you can email me: cjcreeves92@gmail.com
Let me know if I made any mistake, Thanks! I hope this is helpful in some way.
Paul’s tips on how to approach experimental design for the animal exam:
1: Everyone must be aware that the expectations have changed a bit for how we present each experiment. We are now expected to show a control along with each experimental design that we come up with, or we are at a minimum supposed to make reference to our previous controls. He reason for this is that each experiment is supposed to be able to stand on it’s own, and without controls, you really don’t know if the design of your experiments is right, or wrong.
2: with regards to the animal exam, I don’t know for sure, but it seems as if we will be asked to design experiments similar to the one we had in breakouts, i.e. something to do with mutations of receptors and hormones. In the situation we were given in breakouts, we were able to connect two mice together and determine which one had bad hormone receptors, which one had low hormone levels, and which one was okay. Go back over the controls and look at how the results directed our decision-making. Make sure you understand all aspects of what we did. Otherwise, my advice for this experimental design is much the same as for the plant exam, and is as follows:
3: As in any problem given on a test I recommend reading the problem thoroughly and either underlining the actual question, or questions that need to be answered, and circle the essential details given, i.e. any numerical values that must be used to solve the problem. This may seem like a waste of time but I assure you it is not. It is easy in a test to get stressed out and jump around within a problem without fully reading it. Sometimes there is more that one question to be answered and you might get done answering one part of the question, without remembering to finish all parts of the problem.
4: Once you have figured out all the important details and have a clear understanding of what is being asked of you, moving ahead should be relatively straightforward. In experimental design questions you’ll be given a scenario either in words or in illustrations. You may be given the hypothesis or possibly not. If you are not given the hypothesis, the first thing to do is develop one. How should you go about creating one? If you are given the scenario with words, draw a picture of what is being described. Once you have a picture in front of you it may be easier to pick out the details. Look for what is changing in the scenario and come up with a explanation for the change. You can be creative here, as long as it is testable, you can continue through with designing the experiment.
4: Lets go through an example from this point on. I see the following scenario presented to me on a test: Look for Popeye photo on this blog page:
From the pictures given you could formulate a hypothesis that once Popeye eats spinach he can lift 500 lbs. with each arm. (For our purposes we’ll assume that he is lifting 500 lbs. in his left hand too).
BE CAREFUL NOT TO MAKE THE HYPOTHESIS TOO COMPLICATED! Its stressful enough during a test, without making it hard on yourself by coming up with complicated hypothesis.
Before you continue, it is important to list out the possible meanings of different outcomes for each experiment. Make sure it is clear and accurate. You don’t want to set up an experiment that won’t really get to the point of helping you determine if your hypothesis is correct.
Another important point: make sure you are dealing with one variable at a time. Don’t change two variables at the same time; if you do, you won’t be able to determine which variable was the source of change.
How do you test this hypothesis? START WITH CONTROLS! As with the hypothesis, keep things simple. There is no particular order required but starting with controls gets your mind thinking in the right direction.
1: Perform a positive control by carrying out exactly what is pictured. Give Popeye spinach and see if he can lift 500 lbs. in each hand. Here you are verifying that your test conditions are appropriate, and that indeed, after eating spinach, Popeye can lift that much weight. By doing a positive test you are making sure that there isn’t something wrong with your set up.
If Popeye lifts the weights after eating the spinach then your test conditions are appropriate.
If Popeye eats the spinach and can’t lift the weights, then there is something wrong with the conditions of the experiment, Maybe he needs more sleep, or you have just uncovered the fact that spinach doesn’t work for Popeye every time.
2: Perform a negative control. Negative controls are simple; take away the factor that is supposedly making him strong and see if he can lift the weights. For example, don’t let him eat spinach.
If he lifts the weights then obviously, spinach isn’t required to lift that much weight.
If he can’t lift the weights, then you know that there is something about eating spinach that makes him strong enough to lift those weights.
3. Now for the other types of tests. I’ll give a few examples that would help us determine if spinach was the source of his strength.
Give Popeye a can of kale labeled as spinach. This will ensure that he thinks it is spinach, and not other kinds of food, that allow him to lift the weights.
If He can lift the weights then spinach is not required for him to lift those weights.
If he lifts the weights, then you can say that something about eating spinach allows him to lift those weights.
You could try a dose response to see of the amount of spinach he consumed had anything to do with his ability to lift those weights. Vary the amounts of spinach given to Popeye, and then have him lift the weights. For example, give him just a tiny sliver of spinach, followed by increasing amounts between each test.
The pattern of performance will matter for the meanings of the results. For example, if he can’t lift the weights until eating a certain amount, then you know his ability is dose dependent. If he can lift the weights by only eating the smallest fraction of spinach, then you can say that it is not dose dependent.
A transplant experiment would be a bit tough with a person, but since he is a cartoon you could transplant the stomach of another cartoon character that had just consumed spinach, into Popeye and test his abilities to lift the weights.
If he can lift the weights after the transplant, then something about spinach was the cause.
If he can’t lift the weights after the transplant, then something besides digesting spinach is the source of his ability to lift the weights. Maybe it’s the chewing of the spinach? More tests are needed to determine that.
In reality, transplants experiments could get a bit complicated because you would need to make sure that doing a transplants don’t affect the adversely affect your test subject by carrying out a few control experiments after a transplant has been done. Basically, you have to know that that act of doing a transplant on its own won’t affect your results.
In the end, the best advice I could give is to make up your own scenarios and try to solve them. Practice will help you get better in anything you do. DON’T go into the exams without having done a lot of practice. That way, you won’t be as stressed out during the exam.
Chapter 46: Muscle Contraction
• Sensory Transduction (figure 46.2)
All stimuli are converted to electrical signals (action potentials)
When sensory cells are at a resting state the inside is more negative than the outside
If ions flow into the cell the cell becomes more positive (less negative)- depolarized
If the ion flow makes the cell more negative than the resting potential- hyperpolarized
“The frequency of action potentials from a receptor transmits information about the nature and intensity of the sensory stimulus”
• Types of muscles (summary table 46.1)
Skeletal Muscle
Location: Attached to bones
Function: Move skeleton
Cell Characteristics: Multinucleated, unbranched, myofibrils, requires signals for activity
Cardiac Muscle
Location: Heart
Function: Pump blood
Cell Characteristics: 1 or 2 nuclei, Branched; intercalated discs, myofibrils, does not require signals
Smooth Muscle
Location: Intestines, arteries, other
Function: Move food, regulate blood pressure, etc.
Cell Characteristics: Single nucleus, unbranced, no myofibrils, does not require signals
• Myosin and Actin Interaction (figure 46.20)
Changes in conformation of the myosin head produces movement
Step 1: ATP binds to the myosin head
Step 2: ATP is hydrolyzed (ADP + P). The myosin head pivots and binds to new actin subunit
Step 3: The phosphate group is released leaving behind the ADP. The head pivots again and moves the filament (aka power stroke)
Step 4: The ADP is released and the cycle is ready to begin again
• How do action potentials trigger muscle contractions (figure 46.22)
Step 1: Action potential arrives (ACh is released)
Step 2: ACh binds to ACh receptors (triggering depolarization and leads to action potential)
Step 3: Action potential propogate (T-tubules)
Step 4: Calcium channels open (sarcoplasmic reticulum)
Step 5: Calcium is released
“Action potentials at the neuromuscular junction (NMJ) trigger the release of calcium, which binds to troponin- tropmyosin and allows myosin to form a cross bridge with actin”
• Troponin and Tropomyosin (T-Dog)
Relaxation: Both troponin and tropomyosin work together to block the myosin binding sites on actin
Contraction: When calcium ions bind to troponin, the troponin-tropomyosin complex moves (rolls) out of the way and exposes the myosin binding sites on actin
• Sliding filament model (figure 46.18)
Composed of thick filaments and thin filaments that slide past one another during contraction
Thin filaments are composed of two coiled chains of the globular protein actin
Thick filaments are composed of multiple strands of a long protein called myosin and are anchored to the middle of the sarcomere. They are free at both ends to interact with the thin filaments
Autocrine signal: affect the same cell that releases them.
Paracrine signals: affects cells beside them.
Endocrine signals: signals carried by blood and affect distant cells. These signals are usually hormones that are secreted from glands like pituitary, thyroid, parathyroid, and adrenal glands, pineal body, gonads, pancreas, and paraganglia.
Neural signals: these are the signals you see in the axon terminal called neurotransmitters. These signals bind to receptors in postsynaptic cells that induce an action potential to occur.
Neuroendocrine signals: these singals affect distant cells which is also carried by blood. Neuroendocrine cells receive neurotransmitter signals and they release hormones.
Phernomes: release in the environment
Hormone Signaling Pathway
Negative feedback: Cells obtains feedback that inhibits whatever it is producing. Its overall purpose is to maintain homeostasis. Cortisol, for example, signals negative feedback to the hypothalamus and pituitary gland to decrease the production of CRH and ACTH. CRH and ACTH are hormones responsible for releasing glucocorticoids such as cortisol.
Three major classes of hormones
Polypeptides
Amino acid derivative
steroids
Polypeptides and amino acid derivatives bind to receptors on the cell surface. Hormones can also bind to receptors but some can diffuse through a cell membrane and bind to receptors inside the cell. These steroids are called lipid-soluble hormones and they change the rate of gene expression.
Ch 45
Anatomy of a neuron, big ol’ cell body with dendrites coming out of it, long axon tail.
Resting potential is the cell is at rest and there is no signal passing along the membrane of the neuron.
The are low concentrations of Na+ Cl- inside of the cell but there is a large concentration of K+ inside the cell.
Before depolarization Na+ channels open and Na+ comes in
During depolarization K+ leaves the cell because of leaky potassium channels
Then Na+ stops coming in and the channels close
During repolarization K+ channels main open and K+ goes out still
Then K+ channels close and Na+ channels rest
During hyperpolarization extra K+ diffuses back in.
Threshold potential is the amount of charge that has to be met for auction potential to actually occur.
All action potentials for a given neuron are identical in magnitude and duration, no such thing as partial action potential.
Voltage gated channels work like garage doors, outside of membrane is positive and inside is negative, when the outside part of protein is depolarize then the ion can come in (like pressing a button on a garage door).
Voltage gated channels are open or closed.
Neurotoxins suck because it abolishes action potentials.
The space in between the synapse of two neurons is called the synaptic cleft, this is where neurotransmitter are exchanged/destroyed/recycled/taken back up by cell.
Ligands are molecules that binds to a specific site on receptor molecules, many neurotransmitter are Ligands, the receptors are called ligand gated channels.
EPSPs are changes in the postsynaptic cell that make action potentials more likely, EPSPs increased when at resting potential, when Na+ goes into cell.
IPSPs make action potentials less likely, IPSPs increased during hyprpilarization, when K+ flows out and Cl- flows into cell.
Both EPSPs and IPSPs are increased when simultaneous Na+ inflow plus K+ outflow or just Cl- outflow.
Definition:
“The ability of a system or living organism to adjust its internal environment to maintain a stable equilibrium; such as the ability of warm-blooded animals to maintain a constant temperature.”
It is a process of body to maintain balance.
There are negative and positive feedback
A negative feed back mechanism dampens stimulus.
Positive feed backs amplify a stimulus.
For example when sugar is eaten and digested to glucose and released to the blood, insulin is secreted and signaling glucose transporters moving to the cell outer membrane from the inner membrane because now the blood sugar is high and we need to lower it down to the set point by transferring glucose into the cell. Also, when the sugar level of blood is low, a hormone – glucagon will stimulates the release of glycogen and be broken down to glucose, increasing the blood sugar level. That’s neg feedback
Another example is when we exercise, out body temperature increased, our body respond this by sweating and cooling off our body down to the set point. This’s also neg feedback.
Positive feedback doesn’t play a major role in homeostasis. It doesn’t reduce the stimulus like neg feedback does, instead it helps drive the process to completion like childbirth. During childbirth, the pressure of the baby’s head against receptors near the opening of the mother’s uterus stimulates the uterus to contract. These contractions result in greater pressure against the opening of the uterus, heightening the contractions and thereby causing even greater pressure, until the baby is born.
Ch45 Diabetes
Is caused by deficiency of insulin or decreased response to insulin in the cell usually in the insulin receptor. Resulting blood glucose level rise, and became too high.
Type I= lost of ability to produce insulin, the function of producing insulin in pancreas is gone, so nothing is stimulating the insulin receptor therefore no glucose transporter on the surface of cell, and the cell is not up taking glucose, resulting high level of blood sugar.
Type II= insulin receptor not responding, insulin is produced but cell fail to take up glucose because insulin receptor is not responding so glucose transporters are not going to the cell surface. Resulting high sugar level in the blood.
Sample MC questions:
After eating a sugary donut and drinking a soft drink your blood glucose levels rise above a normal range. How would negative feedback affect this variable?
a. Blood glucose levels would rise even further.
b. Blood glucose levels would fall to below what is considered a normal range.
c. Blood glucose levels would return to a normal range (homeostasis).
Shortly after ingesting a big plate of pasta, you measure your blood’s hormone levels. What results would you expect, compared to before the meal?
a. high insulin, low glucagon
b. low insulin, low glucagon
c. high insulin, high glucagon
d. low insulin, high glucagon
e. low insulin, no change in glucagon
Which type of feedback systems are more common in human, positive or negative?
a. positive
b. negative
c. they are both very common
d. they are both extremely rare
BBIO220 Physiology Blog! Whoo Hooo!
http://www.businessinsider.com/your-iphone-will-soon-detect-bad-breath-2013-1
I decided to go off on my own and find another interesting odor fact. Above is a link to an article that introduces a new app that is soon to hit the market. Think smell-o-vision in reverse. This app uses technology like that found in the article about UCSB’s mechanical nose. The technology is able to “take the sense of smell and taste and digitized them”, explains creator Sam Khamis. When finished, this app (actually a device that will plug into your phone) will use 4,000 sensors to tell warn you when you have bad breath! At least it’s better than the person sitting next to you!! Khamis does warn, though, this will not be a device that emits smell, only detects.
NOT ACTUAL POST! Sorry about this. I put this up before the assigned e-mail was sent. My actual post will be on action potential. Sorry!
http://www.sciencecodex.com/female_moths_use_olfactory_signals_to_choose_the_best_egglaying_sites-113274
I thought this was pretty interesting. Check it out. I guess I have never really thought about bugs smelling.
Action Potential Fun Facts!!!
-a rapid, temporary change in membrane potential
-“all or nothing”
-will fire at threshold (-55mV)
-myelin sheath/Schwann Cells coat the axon/insulate so action potential jumps quickly along
-positive feedback
-occurs in milliseconds
-frequency is better than size
-depolarization due to Na+ influx
-repolarization due to K+ outflux
-arrival at axon terminal triggers Ca++ entry thus releasing neurotransmitters
-chain reaction from other dendrites processed at cell body “decided” to be sent out
-works down axon to send signals to neighboring dendrites; to cause an action
Simplified Steps:
1. Signal Received
2. Voltage Gated Na+ Channels open upon -55mV, Na+ enters cell, becomes more +
3. Voltage Gated K+ Channels open upon +40mV, K+ leaves cell, becomes more –
4. Undershoot/hyperpolarization (more negative than resting potential)/Refractory Period
(Prevents action potential from reversing)
*Maintenance of Resting Potential: Na/K Pumps, “Leaky K+” Channels, Organic Proteins.
*Cl- fights between its concentration & electrochemical gradient for entrance into cell, “regulator”.
Quick, easy video description of the above:
If I were to form a question about Action Potentials, I would ask: Many diseases interfere with action potentials in different ways, how can action potentials be interrupted to cause dysfunction?
Chapter 44 Gas Exchange
Diffusion – Flick’s Law of diffusion explains that there are 5 different parameters for diffusion of a gas: solubility of the gas, temperature, surface area, differences in partial pressures, and finally the thickness of the barrier to diffusion.
Gills in fish are so efficient in breathing under water because they have such a large surface area, allowing O2 to diffuse across the thin epithelium. They also have a counter current exchange system which causes water and blood to flow in opposite directions.
SO, we know that in humans, CO2 and O2 are transferred around the body via the blood (veins, arteries, etc.). O2 can easily bind to blood because blood has such a high oxygen carrying capacity. When the binding of successive O2 molecules to a subunit of hemoglobin molecule occurs, this creates a conformational change – the protein can now more easily bind to O2! THIS creates that S-shaped curve on a graph.
The role of Carbonic Anhydrase – When CO2 enters a red blood cell, carbonic anhydrase turns it into an acid, which breaks it down into a bicarbonate ion and proton (creating a partial pressure gradient, allowing CO2 to enter RBCs). – The protons produced then bind to deoxygenated hemoglobin.
This video is from like 1982, but it was pretty helpful! 🙂
This goes really into depth, but it has some useful info
Chapter 44- Circulation
What would Bryan think are the most important things from this section?
I think that Bryan will want us to for sure understand the closed circulatory system. SO… in the closed circulatory system, blood is flowing throughout the body continuously. It flows through the body under pressure that is generated by the heart. The reason that blood can maintain a high flow rate in a close circulatory system is because the blood is confined to vessels. An interesting fact about the closed circulatory system is that blood can be directed where you need it in the body. Vertebrates have a closed circulatory system. Types of blood vessels: arteries- thick walled, take blood away from the heart. Capillaries- walls are just one cell thick, this allows for diffusion of gasses. Veins- these return blood to the heart.
Since capillaries are thin walled, and the pressure of the system is pretty high, fluid steadily leaks from blood vessels to the surrounding space. This fluid is called interstitial fluid. It resembles plasma in it’s electrolyte composition. A lot of this fluid is taken back in by the veins.
The rest of the fluid is collected by the lymphatic system. Once this happens it is then called lymph.
How does the heart work? See picture
High blood pressure=Hypertension
What do I think are the most important things from this section?
I think that the most important things in this section are how a heart works and also memorizing the flow of blood through the heart. I am uploading a picture that I drew along with this so that you can see. It helped me study so maybe it will be helpful for you guys as well.
How can I explain this stuff in an easier way?
All of this stuff is pretty straight forward, I think that it is way easier to memorize on paper how a heart works than it is to apply it in real life. The one thing that will be helpful to remember is that although on diagrams it looks like the blood flows in the superior vena cava through all of the chambers then out the pulmonary artery to the lungs then back in through the pulmonary vein, it is actually happening simultaneously. So blood is flowing in through the Superior vena cava and in through the pulmonary vein at the same time.
What am I still confused about?
In this section I am not really confused about anything. The only thing that maybe I would like to have better explained to me is the homeostatic control of blood pressure.
Question:
We know that backflow thought a valve reduces the efficiency of a heart. But what if both the semi-lunar valves (pulmonary and aortic) were “leaky”, or had backflow. Would the result be just a “double murmur” or would the consequences be direr?
Also check out this video: http://youtu.be/QhiVnFvshZg
I cant figure out how to add the image of the heart that I drew into this comment, so if you are interested in seeing that you can email me: cjcreeves92@gmail.com
Let me know if I made any mistake, Thanks! I hope this is helpful in some way.
Paul’s tips on how to approach experimental design for the animal exam:
1: Everyone must be aware that the expectations have changed a bit for how we present each experiment. We are now expected to show a control along with each experimental design that we come up with, or we are at a minimum supposed to make reference to our previous controls. He reason for this is that each experiment is supposed to be able to stand on it’s own, and without controls, you really don’t know if the design of your experiments is right, or wrong.
2: with regards to the animal exam, I don’t know for sure, but it seems as if we will be asked to design experiments similar to the one we had in breakouts, i.e. something to do with mutations of receptors and hormones. In the situation we were given in breakouts, we were able to connect two mice together and determine which one had bad hormone receptors, which one had low hormone levels, and which one was okay. Go back over the controls and look at how the results directed our decision-making. Make sure you understand all aspects of what we did. Otherwise, my advice for this experimental design is much the same as for the plant exam, and is as follows:
3: As in any problem given on a test I recommend reading the problem thoroughly and either underlining the actual question, or questions that need to be answered, and circle the essential details given, i.e. any numerical values that must be used to solve the problem. This may seem like a waste of time but I assure you it is not. It is easy in a test to get stressed out and jump around within a problem without fully reading it. Sometimes there is more that one question to be answered and you might get done answering one part of the question, without remembering to finish all parts of the problem.
4: Once you have figured out all the important details and have a clear understanding of what is being asked of you, moving ahead should be relatively straightforward. In experimental design questions you’ll be given a scenario either in words or in illustrations. You may be given the hypothesis or possibly not. If you are not given the hypothesis, the first thing to do is develop one. How should you go about creating one? If you are given the scenario with words, draw a picture of what is being described. Once you have a picture in front of you it may be easier to pick out the details. Look for what is changing in the scenario and come up with a explanation for the change. You can be creative here, as long as it is testable, you can continue through with designing the experiment.
4: Lets go through an example from this point on. I see the following scenario presented to me on a test: Look for Popeye photo on this blog page:
From the pictures given you could formulate a hypothesis that once Popeye eats spinach he can lift 500 lbs. with each arm. (For our purposes we’ll assume that he is lifting 500 lbs. in his left hand too).
BE CAREFUL NOT TO MAKE THE HYPOTHESIS TOO COMPLICATED! Its stressful enough during a test, without making it hard on yourself by coming up with complicated hypothesis.
Before you continue, it is important to list out the possible meanings of different outcomes for each experiment. Make sure it is clear and accurate. You don’t want to set up an experiment that won’t really get to the point of helping you determine if your hypothesis is correct.
Another important point: make sure you are dealing with one variable at a time. Don’t change two variables at the same time; if you do, you won’t be able to determine which variable was the source of change.
How do you test this hypothesis? START WITH CONTROLS! As with the hypothesis, keep things simple. There is no particular order required but starting with controls gets your mind thinking in the right direction.
1: Perform a positive control by carrying out exactly what is pictured. Give Popeye spinach and see if he can lift 500 lbs. in each hand. Here you are verifying that your test conditions are appropriate, and that indeed, after eating spinach, Popeye can lift that much weight. By doing a positive test you are making sure that there isn’t something wrong with your set up.
If Popeye lifts the weights after eating the spinach then your test conditions are appropriate.
If Popeye eats the spinach and can’t lift the weights, then there is something wrong with the conditions of the experiment, Maybe he needs more sleep, or you have just uncovered the fact that spinach doesn’t work for Popeye every time.
2: Perform a negative control. Negative controls are simple; take away the factor that is supposedly making him strong and see if he can lift the weights. For example, don’t let him eat spinach.
If he lifts the weights then obviously, spinach isn’t required to lift that much weight.
If he can’t lift the weights, then you know that there is something about eating spinach that makes him strong enough to lift those weights.
3. Now for the other types of tests. I’ll give a few examples that would help us determine if spinach was the source of his strength.
Give Popeye a can of kale labeled as spinach. This will ensure that he thinks it is spinach, and not other kinds of food, that allow him to lift the weights.
If He can lift the weights then spinach is not required for him to lift those weights.
If he lifts the weights, then you can say that something about eating spinach allows him to lift those weights.
You could try a dose response to see of the amount of spinach he consumed had anything to do with his ability to lift those weights. Vary the amounts of spinach given to Popeye, and then have him lift the weights. For example, give him just a tiny sliver of spinach, followed by increasing amounts between each test.
The pattern of performance will matter for the meanings of the results. For example, if he can’t lift the weights until eating a certain amount, then you know his ability is dose dependent. If he can lift the weights by only eating the smallest fraction of spinach, then you can say that it is not dose dependent.
A transplant experiment would be a bit tough with a person, but since he is a cartoon you could transplant the stomach of another cartoon character that had just consumed spinach, into Popeye and test his abilities to lift the weights.
If he can lift the weights after the transplant, then something about spinach was the cause.
If he can’t lift the weights after the transplant, then something besides digesting spinach is the source of his ability to lift the weights. Maybe it’s the chewing of the spinach? More tests are needed to determine that.
In reality, transplants experiments could get a bit complicated because you would need to make sure that doing a transplants don’t affect the adversely affect your test subject by carrying out a few control experiments after a transplant has been done. Basically, you have to know that that act of doing a transplant on its own won’t affect your results.
In the end, the best advice I could give is to make up your own scenarios and try to solve them. Practice will help you get better in anything you do. DON’T go into the exams without having done a lot of practice. That way, you won’t be as stressed out during the exam.
Chapter 46: Muscle Contraction
• Sensory Transduction (figure 46.2)
All stimuli are converted to electrical signals (action potentials)
When sensory cells are at a resting state the inside is more negative than the outside
If ions flow into the cell the cell becomes more positive (less negative)- depolarized
If the ion flow makes the cell more negative than the resting potential- hyperpolarized
“The frequency of action potentials from a receptor transmits information about the nature and intensity of the sensory stimulus”
• Types of muscles (summary table 46.1)
Skeletal Muscle
Location: Attached to bones
Function: Move skeleton
Cell Characteristics: Multinucleated, unbranched, myofibrils, requires signals for activity
Cardiac Muscle
Location: Heart
Function: Pump blood
Cell Characteristics: 1 or 2 nuclei, Branched; intercalated discs, myofibrils, does not require signals
Smooth Muscle
Location: Intestines, arteries, other
Function: Move food, regulate blood pressure, etc.
Cell Characteristics: Single nucleus, unbranced, no myofibrils, does not require signals
• Myosin and Actin Interaction (figure 46.20)
Changes in conformation of the myosin head produces movement
Step 1: ATP binds to the myosin head
Step 2: ATP is hydrolyzed (ADP + P). The myosin head pivots and binds to new actin subunit
Step 3: The phosphate group is released leaving behind the ADP. The head pivots again and moves the filament (aka power stroke)
Step 4: The ADP is released and the cycle is ready to begin again
• How do action potentials trigger muscle contractions (figure 46.22)
Step 1: Action potential arrives (ACh is released)
Step 2: ACh binds to ACh receptors (triggering depolarization and leads to action potential)
Step 3: Action potential propogate (T-tubules)
Step 4: Calcium channels open (sarcoplasmic reticulum)
Step 5: Calcium is released
“Action potentials at the neuromuscular junction (NMJ) trigger the release of calcium, which binds to troponin- tropmyosin and allows myosin to form a cross bridge with actin”
• Troponin and Tropomyosin (T-Dog)
Relaxation: Both troponin and tropomyosin work together to block the myosin binding sites on actin
Contraction: When calcium ions bind to troponin, the troponin-tropomyosin complex moves (rolls) out of the way and exposes the myosin binding sites on actin
• Sliding filament model (figure 46.18)
Composed of thick filaments and thin filaments that slide past one another during contraction
Thin filaments are composed of two coiled chains of the globular protein actin
Thick filaments are composed of multiple strands of a long protein called myosin and are anchored to the middle of the sarcomere. They are free at both ends to interact with the thin filaments
Chapter 46 related videos:
https://www.khanacademy.org/science/biology/human-biology/v/myosin-and-actin
https://www.khanacademy.org/science/biology/human-biology/v/tropomyosin-and-troponin-and-their-role-in-regulating-muscle-contraction
Ch. 47 Chemical Signals in Animals
Six major types of chemical signals
Autocrine signal: affect the same cell that releases them.
Paracrine signals: affects cells beside them.
Endocrine signals: signals carried by blood and affect distant cells. These signals are usually hormones that are secreted from glands like pituitary, thyroid, parathyroid, and adrenal glands, pineal body, gonads, pancreas, and paraganglia.
Neural signals: these are the signals you see in the axon terminal called neurotransmitters. These signals bind to receptors in postsynaptic cells that induce an action potential to occur.
Neuroendocrine signals: these singals affect distant cells which is also carried by blood. Neuroendocrine cells receive neurotransmitter signals and they release hormones.
Phernomes: release in the environment
Hormone Signaling Pathway
Negative feedback: Cells obtains feedback that inhibits whatever it is producing. Its overall purpose is to maintain homeostasis. Cortisol, for example, signals negative feedback to the hypothalamus and pituitary gland to decrease the production of CRH and ACTH. CRH and ACTH are hormones responsible for releasing glucocorticoids such as cortisol.
Three major classes of hormones
Polypeptides
Amino acid derivative
steroids
Polypeptides and amino acid derivatives bind to receptors on the cell surface. Hormones can also bind to receptors but some can diffuse through a cell membrane and bind to receptors inside the cell. These steroids are called lipid-soluble hormones and they change the rate of gene expression.
Ch 45
Anatomy of a neuron, big ol’ cell body with dendrites coming out of it, long axon tail.
Resting potential is the cell is at rest and there is no signal passing along the membrane of the neuron.
The are low concentrations of Na+ Cl- inside of the cell but there is a large concentration of K+ inside the cell.
Before depolarization Na+ channels open and Na+ comes in
During depolarization K+ leaves the cell because of leaky potassium channels
Then Na+ stops coming in and the channels close
During repolarization K+ channels main open and K+ goes out still
Then K+ channels close and Na+ channels rest
During hyperpolarization extra K+ diffuses back in.
Threshold potential is the amount of charge that has to be met for auction potential to actually occur.
All action potentials for a given neuron are identical in magnitude and duration, no such thing as partial action potential.
Voltage gated channels work like garage doors, outside of membrane is positive and inside is negative, when the outside part of protein is depolarize then the ion can come in (like pressing a button on a garage door).
Voltage gated channels are open or closed.
Neurotoxins suck because it abolishes action potentials.
The space in between the synapse of two neurons is called the synaptic cleft, this is where neurotransmitter are exchanged/destroyed/recycled/taken back up by cell.
Ligands are molecules that binds to a specific site on receptor molecules, many neurotransmitter are Ligands, the receptors are called ligand gated channels.
EPSPs are changes in the postsynaptic cell that make action potentials more likely, EPSPs increased when at resting potential, when Na+ goes into cell.
IPSPs make action potentials less likely, IPSPs increased during hyprpilarization, when K+ flows out and Cl- flows into cell.
Both EPSPs and IPSPs are increased when simultaneous Na+ inflow plus K+ outflow or just Cl- outflow.
Ch41: Homeostasis
Definition:
“The ability of a system or living organism to adjust its internal environment to maintain a stable equilibrium; such as the ability of warm-blooded animals to maintain a constant temperature.”
It is a process of body to maintain balance.
There are negative and positive feedback
A negative feed back mechanism dampens stimulus.
Positive feed backs amplify a stimulus.
For example when sugar is eaten and digested to glucose and released to the blood, insulin is secreted and signaling glucose transporters moving to the cell outer membrane from the inner membrane because now the blood sugar is high and we need to lower it down to the set point by transferring glucose into the cell. Also, when the sugar level of blood is low, a hormone – glucagon will stimulates the release of glycogen and be broken down to glucose, increasing the blood sugar level. That’s neg feedback
Another example is when we exercise, out body temperature increased, our body respond this by sweating and cooling off our body down to the set point. This’s also neg feedback.
Positive feedback doesn’t play a major role in homeostasis. It doesn’t reduce the stimulus like neg feedback does, instead it helps drive the process to completion like childbirth. During childbirth, the pressure of the baby’s head against receptors near the opening of the mother’s uterus stimulates the uterus to contract. These contractions result in greater pressure against the opening of the uterus, heightening the contractions and thereby causing even greater pressure, until the baby is born.
Ch45 Diabetes
Is caused by deficiency of insulin or decreased response to insulin in the cell usually in the insulin receptor. Resulting blood glucose level rise, and became too high.
Type I= lost of ability to produce insulin, the function of producing insulin in pancreas is gone, so nothing is stimulating the insulin receptor therefore no glucose transporter on the surface of cell, and the cell is not up taking glucose, resulting high level of blood sugar.
Type II= insulin receptor not responding, insulin is produced but cell fail to take up glucose because insulin receptor is not responding so glucose transporters are not going to the cell surface. Resulting high sugar level in the blood.
Sample MC questions:
After eating a sugary donut and drinking a soft drink your blood glucose levels rise above a normal range. How would negative feedback affect this variable?
a. Blood glucose levels would rise even further.
b. Blood glucose levels would fall to below what is considered a normal range.
c. Blood glucose levels would return to a normal range (homeostasis).
Shortly after ingesting a big plate of pasta, you measure your blood’s hormone levels. What results would you expect, compared to before the meal?
a. high insulin, low glucagon
b. low insulin, low glucagon
c. high insulin, high glucagon
d. low insulin, high glucagon
e. low insulin, no change in glucagon
Which type of feedback systems are more common in human, positive or negative?
a. positive
b. negative
c. they are both very common
d. they are both extremely rare