You decide to run an experiment in the lab in which you stimulate a neuron two t

Question

You decide to run an experiment in the lab in which you stimulate a neuron two times. If you wait 10 ms between the two stimulations, you can record normal action potentials each time. A. If you only wait 2 ms between stimuli, you are unable to record a second action potential using the same stimulus that caused the first action potential. To remedy this, you apply a larger stimulus to the neuron and are once again able to record action potentials. Name and explain this phenomenon. B. If you switch to a 1 ms interval between stimuli, even increasing the amplitude of the second stimulus does not elicit an action potential. Why is this the case?

Explanation / Answer

A. This phenomenon is known as all or none phenomenon which means if intensity of stimulus is increased, the size of action potential does not increase rather the frequency of action potential increases. It means the amplitude of action potential is always same and the number of action potential changes with change in intensity of stimulus. Therfore you can record normal action potential even after waiting 2ms only by enhancing the stimulus intensity.

B. If you switch to 1ms interval you can not record the second action potential because of absolute refractory period which is almost equal to 1 ms. Absolute refractory period indicates the maximum possible frequency of action potential. Thus, you cannot record the 2nd action potential at interval of 1ms even after applying a huge intensity of stimulus.

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