Activity 4:  Generation of Action Potentials

This is the one I need help on also....

Did you end up with the answers?

I need help also

No. Still need help.

I need help too!

Post Merge: 9 years ago

Do you have the answers to this?

PREDICTIONS

1.  Urine output will be highest during: water loading

2.  Urine osmolality will be lowest during: normal hydration

3. Plasma osmolality: increases with dehydration


METHODS AND MATERIALS

1. Dependent variable: urine and plasma values

2. Independent variable: fluid intake

3. Controlled variables: age, gender, and weight


4. Subjects were asked to refrain from alcohol and caffeine for a day before the start of the experiment. Explain why this is important.
It’s important because alcohol and caffeine will increase urine output.


5. What technique was used to measure urine and plasma osmolality?
Water consumption measured urine output, and a finger stick. An
osmometer was used to check osmolarity
Water consumption measured urine output, and a finger stick. An
osmometer was used to check osmolarity
Water consumption measured urine output, and a finger stick. An
osmometer was used to check osmolarity
The water consumption measured the urine output, and the finger stick. The osometer was used to check the osmolality.

RESULTS
See Table 3: Urine Production Rate
See Graph 1: Average Daily Urine Production Under Different Hydration States


Type in the following AVERAGE urine production rate (L/day)
•   Normal
•   Dehydrated
•   Water Loaded




   Normal
30min (mL)      L/day   Dehydrated
30min (mL)      L/day   Water Loaded
30min (mL)      L/day
Subject 1   44.6                    2.14   13.5                    0.65   147.2                 7.07
Subject 2   43.1                    2.07   14.6                     0.7   142.2                 6.84
Subject 3   40.7                    1.95   14.6                     0.7   148.3                 7.12
Average                               2.05                               0.68                              7.01


1. Does dehydration increase, decrease, or not change average urine production rate (L/day)? Dehydration decreases urine production rate.


2. Does water loading increase, decrease, or not affect average urine production rate (L/day)? Water loading increases urine production rate enormously.


See Table 4: Osmolality (mosm/L)
See Graph 2: Blood Plasma and Urine Osmolality Under Different Hydration States
  Type in the following AVERAGE urine osmolality (mosm/L)
•   Normal
•   Dehydrated
•   Water Loaded

Urine

   Normal   Dehydrated   Water Loaded
Subject 1   599   1180   227
Subject 2   573   1220   167
Subject 3   592   1220   160
Average   588   1207   185


3. Does dehydration increase, decrease, or not change average urine osmolality (mosm/L)? Dehydration increases urine osmolality.


4. Does water loading increase, decrease, or not change average urine osmolality (mosm/L)? Water loading decreases urine osmolality.

Type in the following AVERAGE plasma osmolality (mosm/L)
•   Normal
•   Dehydrated
•   Water Loaded

Plasma

   Normal   Dehydrated   Water Loaded
Subject 1   296   298   271
Subject 2   285   294   274
Subject 3   292   293   273
Average   291   295   273


5. Does dehydration increase, decrease, or not change average plasma osmolality (mosm/L)? The average plasma osmolality does not change with dehydration.


6. Does water loading increase, decrease, or not change average plasma osmolality (mosm/L)? Even when the plasma osmolality is water loaded it still does not change.


DISCUSSION

1. State whether dehydration results in production of a concentrated or dilute urine.
Dehydration does not result in diluted urine but rather in concentrated urine.

2. State whether water loading results in production of concentrated or dilute urine.
Water loading, however, the results will show that the urine is diluted.

3. Describe how ADH secretion during dehydration changes urine production and osmolality. ADH secretion during dehydration changes urine production by aiding in the change of reabsorption. When the body is dehydrated, it will release more ADH. This will cause reabsorption of water, giving the body more blood volume, and lower osmolality.


4. Describe how ADH secretion during water loading changes urine production and osmolality. ADH secretion during water loading changes the urine production by allowing more water to be secreted and less water to be absorbed. The osmolality becomes less concentrated.

5. Describe how ADH secretion maintains plasma osmolality levels during dehydration and water loading. ADH lowers plasma osmolality. Dehydration and water loading affects plasma volume, not osmolality, so it’s hard to say what ADH will do.

6. Explain why in this experiment you did not see significant changes in plasma osmolality during dehydration or water later loading.
There isn’t much change because when our bodies are dehydrated or water loaded then ADH will stop because the osmolality effect, so our bodies will just stay dehydrated or filled with water.

7. Discuss why maintaining plasma osmolality within normal limits is important.
If plasma osmolality it is not maintained it can damage the kidneys and other organs in the body.

   Normal
30min (mL)      L/day   Dehydrated
30min (mL)      L/day   Water Loaded
30min (mL)      L/day
Subject 1   44.6                    2.14   13.5                    0.65   147.2                 7.07
Subject 2   43.1                    2.07   14.6                     0.7   142.2                 6.84
Subject 3   40.7                    1.95   14.6                     0.7   148.3                 7.12
Average                               2.05                               0.68                              7.01


1. Does dehydration increase, decrease, or not change average urine production rate (L/day)? Dehydration decreases urine production rate.


2. Does water loading increase, decrease, or not affect average urine production rate (L/day)? Water loading increases urine production rate enormously.


See Table 4: Osmolality (mosm/L)
See Graph 2: Blood Plasma and Urine Osmolality Under Different Hydration States
  Type in the following AVERAGE urine osmolality (mosm/L)
•   Normal
•   Dehydrated
•   Water Loaded

Urine

   Normal   Dehydrated   Water Loaded
Subject 1   599   1180   227
Subject 2   573   1220   167
Subject 3   592   1220   160
Average   588   1207   185


3. Does dehydration increase, decrease, or not change average urine osmolality (mosm/L)? Dehydration increases urine osmolality.


4. Does water loading increase, decrease, or not change average urine osmolality (mosm/L)? Water loading decreases urine osmolality.

Type in the following AVERAGE plasma osmolality (mosm/L)
•   Normal
•   Dehydrated
•   Water Loaded

Plasma

   Normal   Dehydrated   Water Loaded
Subject 1   296   298   271
Subject 2   285   294   274
Subject 3   292   293   273
Average   291   295   273


5. Does dehydration increase, decrease, or not change average plasma osmolality (mosm/L)? The average plasma osmolality does not change with dehydration.


6. Does water loading increase, decrease, or not change average plasma osmolality (mosm/L)? Even when the plasma osmolality is water loaded it still does not change.


DISCUSSION

1. State whether dehydration results in production of a concentrated or dilute urine.
Dehydration does not result in diluted urine but rather in concentrated urine.

2. State whether water loading results in production of concentrated or dilute urine.
Water loading, however, the results will show that the urine is diluted.

3. Describe how ADH secretion during dehydration changes urine production and osmolality. ADH secretion during dehydration changes urine production by aiding in the change of reabsorption. When the body is dehydrated, it will release more ADH. This will cause reabsorption of water, giving the body more blood volume, and lower osmolality.


4. Describe how ADH secretion during water loading changes urine production and osmolality. ADH secretion during water loading changes the urine production by allowing more water to be secreted and less water to be absorbed. The osmolality becomes less concentrated.

5. Describe how ADH secretion maintains plasma osmolality levels during dehydration and water loading. ADH lowers plasma osmolality. Dehydration and water loading affects plasma volume, not osmolality, so it’s hard to say what ADH will do.

6. Explain why in this experiment you did not see significant changes in plasma osmolality during dehydration or water later loading.
There isn’t much change because when our bodies are dehydrated or water loaded then ADH will stop because the osmolality effect, so our bodies will just stay dehydrated or filled with water.

7. Discuss why maintaining plasma osmolality within normal limits is important.
If plasma osmolality it is not maintained it can damage the kidneys and other organs in the body.

7. Discuss why maintaining plasma osmolality within normal limits is important.
If plasma osmolality it is not maintained it can damage the kidneys and other organs in the body.

8. Restate your predictions that were correct and give the data from your experiment that supports them. Restate your predictions that were not correct and correct them, giving the data from your experiment that supports the correction.
My first prediction was that the urine output would be highest during water loading. This prediction is true because all the water is not being absorbed by ADH. It causes the uring to be diluted. My second prediction was urine osmolality would be lowest during normal hydration. This is not true. The urine osmolality is lowest when the body is dehydrated. My last prediction was that plasma osmolality will increase with dehydration, when, in fact, plasma osmolality does not change during any of the experiments.

APPLICATION

1. Drinking alcoholic or caffeinated beverages increases urine output more than drinking an equivalent amount of water.  

•   How do you think these beverages affect ADH secretion? This occurs because alcohol blocks the release of ADH that is needed for water reabsorption.

•   Would urine osmolality be increased or decreased? Urine osmolality will decrease. This will result in decreased water reabosorption, diluted urine, and concentrated blood plasma.


2. Explain why someone with diabetes insipidus must drink more water than normal.
They need to drink more water than normal because they have a lower amount of ADH in their body. If ADH doesn’t work right then there is a rapid loss of water in the urine.

3. Explain what happens to plasma osmolality when you give a severely dehydrated person large amounts of pure water. The cells in the body have absorbed a lot of water, which can result in shock. We want to replace the electrolytes in the body by using a special IV solution.

Just seeing if anyone was able to come up with the answers to the Power Phys #4 for Action Potential?

Post Merge: 9 years ago

Activity 4:  Generation of Action Potentials
Name:
Instructor:
Date:


PREDICTIONS

1.  Exceeding the threshold depolarization at the trigger zone ______ the likelihood of generation of action potential.

2.  Action potential amplitude:

3.  Increasing frequency of stimulation to the trigger zone:


MATERIALS AND METHODS

Experiment 1:  Effect of Stimulus Strength on Action Potential Generation

1. Dependent Variable

2. Independent Variable

3. Controlled Variables

Experiment 2:  Effect of Frequency of Stimulation on Action Potential Generation

1. Dependent Variable

2. Independent Variable

3. Controlled Variables


4. Which part of the neuron was stimulated?


5. Where was membrane potential measured?


6. What was used to measure membrane potential?


RESULTS

See Table 3:  Membrane Potentials at Different Stimulation Voltages, by Location
See Graph 1:  Maximal depolarization of membrane potential at axon hillock and axon after different stimulation voltages.


1. What was the resting membrane potential (no stimulation) recorded in Table 3?


2. At which stimulation voltage(s) did you see decrimental conduction of graded potential from axon hillock to axon?


3. At what stimulus voltage(s) did an action potential occur?


4. What was the membrane potential at the axon hillock when the action potential was generated?


5.  For each of the stimulation voltages, indicate whether it was sub-threshold, threshold, or suprathreshold.
•   2 V
•   4 V
•   6 V
•   8 V


See Table 4:  Effect of Supra-Threshold Stimulation Frequency on Action Potential Generation.
See Graph 2:  Number of action potentials generated at different times between simulations.


6. State the amount of time between stimulations for each frequency of stimulation. 
•   25 Hz
•   50 Hz
•   100 Hz
•   200 Hz
•   400 Hz


7.  For each frequency of stimulation, indicate whether the period between stimulation is longer or shorter than the length of an action potential.  Length of action potential in pyramidal neuron is about 15-20 milliseconds (msec)
•   25 Hz
•   50 Hz
•   100 Hz
•   200 Hz
•   400 Hz


8. Estimate the length of the refractory period for the pyramidal neuron.


DISCUSSION

1. In Experiment 1, discuss why the amplitude of the action potential did not increase as stimulation voltage increased above threshold.


2. In Experiment 1, explain why the membrane potential between the axon hillock and axon either changed or did not change with subthreshold stimulus.  Differences of
1.0 mV or less are not significant


3. In Experiment 2, explain why the membrane potential between the axon hillock and axon either changed or did not change with threshold stimulus. Differences of 1.0 mV or less are not significant


4. In Experiment 2, explain why the number of action potentials generated varied with increased stimulation frequency.


5. Restate your predictions that were correct and give the data from your experiment that supports them. Restate your predictions that were not correct and correct them, giving the data from your experiment that supports the correction.






APPLICATION

1. ECF potassium levels affect resting membrane potential.  Hyperkalemia (excessive levels of potassium in the blood) and hypokalemia (abnormally low blood potassium levels) both affect the function of nerves and muscles.

•   Explain how hyperkalemia will initially affect the resting membrane potential and the generation of an action potential.

•   Explain how hypokalemia will initially affect the resting membrane potential and the generation of an action potential.


2. Tetrodotoxin, a toxin found in puffer fish, acts by inhibiting voltage-gated sodium channels.  Eating improperly prepared puffer fish sushi can be fatal because of interference with action potential generation.  Explain how tetrodotoxin interferes with action potential generation.



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Best to post one question at a time in a new thread.

did you find the answer for question 8? "estimate the length of the refractory period for pyramidal neuron?

I believe the answer is 1.