PEX-03-05 - Physio Ex 9.1 PDF

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Physio Ex 9.1...

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Name: Steffany A Rivera Exercise 3: Neurophysiology of Nerve Impulses: Activity 5: The Action Potential: Measuring Its Absolute and Relative Refractory Periods Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. Which of the following occurs after the peak of the action potential? You correctly answered: d. All of these occur. 2. What is meant by Na+ channel inactivation? You correctly answered: b. The Na+ channel no longer allows Na+ ions to pass through it. 3. What happens when voltage-gated K+ channels open? You correctly answered: d. All of these occur. 4. It is harder to generate a second action potential soon after the first action potential because You correctly answered: d. All of these make it harder to generate a second action potential.

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Experiment Results Predict Question: Predict Question: If you further decrease the interval between the stimuli, will the threshold for the second action potential change? Your answer : a. The threshold for the second action potential will be lower (requiring a smaller depolarization). Stop & Think Questions: Threshold can be defined as the minimum voltage needed to generate an action potential. Is the threshold for the first action potential the same as, or different from, the threshold for the second action potential with a 60 msec interval? Your answer : b. The threshold for the first action potential is the same as the threshold for the second action potential. Correct answer: a. The threshold for the first action potential is lower than the threshold for the second action potential. Experiment Data: Interval Between Stimuli (msec)

Stimulus Voltage (mV)

Second Action Potential?

250 125 60 60 60 30

20 20 20 25 30 30

Yes Yes No No Yes No

30 30 30 15 7.5

35 40 45 60 60

No No Yes Yes Yes

3.75

60

No

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Post-lab Quiz Results You scored 60% by answering 3 out of 5 questions correctly. 1. What is the original threshold for this neuron? You correctly answered: a. A 20 mV depolarization to -50 mV. 2. As the interval between stimuli decreases, the depolarization needed to generate the second action potential You correctly answered: a. increases. 3. Judging from your results, what time period after the first action potential best describes the relative refractory period (the time when a second action potential can be generated only if the stimulus intensity is increased)? Your answer: b. 60-125 msec Correct answer: c. 7.5 ms-60 msec 4. At what interval between stimuli did the second action potential fail, regardless of the stimulus intensity? You correctly answered: d. 3.75 msec 5. What is the absolute refractory period for this neuron? Your answer: b. 60 msec Correct answer: d. 3.75 msec

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Review Sheet Results 1. Define inactivation as it applies to a voltage-gated sodium channel. Your answer: inactivation is when the gated channels are closed and do not allow any ions in or out of the cell 2. Define the absolute refractory period. Your answer: time after an action potential when the neuron cannot fire a second action potential 3. How did the threshold for the second action potential change as you further decreased the interval between the stimuli? How well did the results compare with your prediction? Your answer: The threshold for the second action potential will be higher. The prediction did not compare to the data obtained from the activity. 4. Why is it harder to generate a second action potential during the relative refractory period? Your answer: it is harder because some of the sodium channels are still open as well as the potassium channels

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