Physio EX-03-03 PDF

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Name: Lily Rosenblum Exercise 3: Neurophysiology of Nerve Impulses: Activity 3: The Action Potential: Threshold Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. Axons are You correctly answered: d. long, thin structures that extend from a neuronal cell body. 2. Which of the following is easier? You correctly answered: a. extracellular recordings of the action potential 3. An action potential is usually initiated in an axon at or near You correctly answered: d. all of the above 4. The initiation of an action potential in a sensory neuron in the body normally You correctly answered: a. follows a sufficiently large depolarizing receptor potential.

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Experiment Results Predict Question: Predict Question: How will the action potential at R1 (or R2) change as you continue to increase the stimulus voltage? Your answer : b. The peak value of the action potential will increase. Stop & Think Questions: Why is the action potential recorded by the second recording electrode (R2) delayed relative to the action potential recorded by the first recording electrode (R1)? You correctly answered: c. The action potential had to propagate from R1 to R2. An increase in extracellular K+ would depolarize a neuron. This depolarization would occur if neurons were damaged. From what you have just learned about generating an action potential, what effect would this have on nearby axons? The nearby axonal membranes will ___________. You correctly answered: b. be depolarized to values near or above threshold voltages. Experiment Data: Stimulus Voltage (mV) 10 20 30 40 50

Peak Value at R1 (µV) 0 100 100

Peak Value at R2 (µV) 0 100 100

100 100

100 100

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Action Potential No Yes Yes Yes Yes

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Post-lab Quiz Results You scored 100% by answering 3 out of 3 questions correctly. 1. The threshold voltage in an axon is usually You correctly answered: a. less negative than the resting membrane potential. 2. If a graded receptor potential made the resting membrane potential of the axon more negative (for example, -70 mV changes to -75 mV), you would expect You correctly answered: d. it to be more difficult for this axon to reach the threshold voltage. 3. Failure to reach the threshold voltage in the axon of a sensory neuron could be caused by You correctly answered: d. all of the above.

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Review Sheet Results 1. Define the term threshold as it applies to an action potential. Your answer: Threshold is the minimum stimulus used to generate an action potential. 2. What change in membrane potential (depolarization or hyperpolarization) triggers an action potential? Your answer: The movement of potassium ion efflux causes the membrane potential to depolarize which results in an action potential. 3. How did the action potential at R1 (or R2) change as you increased the stimulus voltage above the threshold voltage? How well did the results compare with your prediction? Your answer: As the stimulus voltage increased there was no change in action potential. When a threshold occured there is the only point it reaches and action potential is fixed whenever it occurs. My prediction did not match my results. 4. An action potential is an "all-or-nothing" event. Explain what is meant by this phrase Your answer: The action potential either happens or doesn't based on what the level of the stimulus is. 5. What part of a neuron was investigated in this activity? Your answer: The axon was what we looked at during this activity.

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