Physioex 8 Exercise 3

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Exercise 3: Neurophysiology of Nerve Impulses Worksheet
Assignment Due: Week 4

Student instructions: Follow the step-by-step instructions for this exercise found in your text and record your answers in the spaces below. Submit this completed document by the assignment due date found in the Syllabus.

Eliciting a Nerve Impulse
Activity 1: Electrical Stimulation

1. Do you see any kind of response on the oscilloscope screen? Just a flat line. 2. What was the threshold voltage, or the voltage at which you first saw an action potential? 3.0 V 3. How does this tracing compare to the one that was generated at the threshold voltage? Very similar except that it's peak is a little higher while it drops a little more as well. 4. What reason can you give for the change? The higher the voltage the more "excitable" the signal gets. 5. Record this maximal voltage here: 4.5 V

Activity 2: Mechanical Stimulation

1. When the glass rod is touching the nerve, what do you see on the oscilloscope screen? Another tracing. 2. How does this tracing compare with the other tracings you have generated? It is the same as the threshold trace at 3.0V.

Activity 3: Thermal Stimulation

1. What happens when the heated rod touches the nerve? It produces a trace. 2. How does this trace compare to the trace that was generated with the unheated glass bar? It is slightly more "excited" than the threshold trace but less than the maximum trace. 3. What explanation can you provide for this? Because of the heat on the bar the ions move faster than at room temperature.

Activity 4: Chemical Stimulation

1. Does the sodium chloride generate an action potential? Yes. 2. Does this tracing differ from the original threshold stimulus tracing? If so, how? No, it's the same. 3. Does the hydrochloric acid generate an action potential? Yes. 4. Does this tracing differ from the original threshold stimulus tracing? If so,...
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