5) Question 5 (5 pt) You are characterizing the firing rate of a neuron by conti

Question

5) Question 5 (5 pt) You are characterizing the firing rate of a neuron by continuously injecting different amounts of current into the cell. You plot the results: a. (1 pt) From this data, what would you conclude is the duration of the absolute refractory period of the neuron? Briefly explain your thinking.



b. (2 pts) Briefly explain (1-2 sentence) the difference in the mechanisms underlying these two types of refractory periods.



c. (2 pts) The neuron you characterized above is a pain-sensing neuron (“nociceptor”) from a person with a disorder that makes them hyper-sensitive to pain. You believe the condition is caused by the neuron firing at a higher than normal rate when stimulated. Come up with an idea for a drug that would act on a voltage gated ion channel to help this person. Remember: we want to keep the person’s ability to feel pain, but we want to reduce the pain they feel. For that reason, the drug should reduce, not eliminate, the firing rate. Explain how your drug would work and describe (or insert a sketch of) how the shape of the action potential would change after adding the drug. Firing Rate vs. Simulating Current 500 450 400 N 350 C 300 250 200 150 100 50 50 100 150 200 250 Injected Current (pA)

Explanation / Answer

A) The period immediately following the action potential of a neuron/muscle is known as refractory period. During the refractory period, the nerve cannot be stimulated by stimulus of any strength. The duration of refractory period ranges from 1-2 milli seconds.

B) Refractory period consists of two phases: absolute and relative. In absolute refractory period, the nerve cannot be stimulated whatever may be the strength of stimulus. In relative refractory period, of the strength of applied stimulus is increased, the nerves can be stimulated.

C) The feeling of excessive pain may be due to minimal or absence of refractory period. The nerves fire very frequently resulting in the perception of greater pain intensity.

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