Physioex 8.0 Ex. 3

Topics: Action potential, Axon, Neuron Pages: 3 (680 words) Published: September 13, 2011
Review Sheet
Exercise 3
Neurophysiology of Nerve Impulses

Eliciting (Generating) a Nerve Impulse
1.Why don’t the terms depolarization and action potential mean the same thing? Because depolarization is the shift in electrical potential across a plasma membrane toward 0 to mV and action potential is a rapid voltage change in which a plasma membrane briefly reverses polarity.

2.What was the threshold voltage in Activity 1? 3.0
3.What was the effect of increasing the voltage? How does this change correlate to changes in the nerve? The nerve showed a change when the voltage was increased to 3.5, and another when increased to 4.0. However, it didn’t change at all when the voltage exceeded 4.0. The nerve was more excited at 3.5 and 4.0 volts, but became constant after 4.0 volts.

4.How did the action potential generated with the unheated rod compare to that generated with the heated rod? The action potential showed the same trace at 3.0 with the unheated rod, then changed with the heated rod at 3.5
5.Describe the types of stimuli that generated an action potential. The voltage when increased to 3 stimulated the nerve cell, the sodium chloride, and the hydrochloric acid all generated an action potential.

6.If you were to spend a lot of time studying nerve physiology in the laboratory, what type of stimulus would you use and why? I would use the heat because it created the action potential faster.

7.Why does the addition of sodium chloride elicit an action potential? Hint: Think about the sodium permeability of the neuron (Figure 3.2e). Sodium chloride is adequately intense threshold stimulus and causes the Na+ to rush into the cell, which increases the number of positive ions inside the cell. This is part of depolarization and when it reaches a certain point, an action potential happens.

Inhibiting a Nerve Impulse
8.What was the effect of...
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