Complete each sentence to review your understanding of action potential initiati

Question

Complete each sentence to review your understanding of action potential initiation and refractory periods An experimentor uses an electrical stimulator to inject a resting neuron with 3 different currents: 5, 10, and 25 microamps. No action potential occurs at 5 and 10 microamps, so those are called K* would not An action potential does occur at 25 microamps, so it is called a threshold stimulus afterhyperpolarization If the neuron was stimulated with a 50 microamp current, an action potential would be occur, and it in size to the 25 microamp-induced action potential. closed During the action potential, a second stimulus, no matter how strong, will not produce a second action potential because the membrane is in its absolute refractory period. arger This occurs because the voltage-gated to the channels are either already open or have proceeded state open Immediately after an action potential, some of the voltage-gated the membrane are still channels that repolarized relative refractory inactivated During this time, a second action potential can be produced, but only if the stimulus strength is than usual similar would This is the period, which coincides roughly with the period of subthreshold stimuli During this time, some of the voltage-gated Na channels have returned to their could therefore open again. state, and Na

Explanation / Answer

An experimenter uses an electrical stimulator to inject a resting neuron with 3 different currents; 5, 10 and 25 microamps. No action potential occurs at 5 and 10 microamps, so those are called subthreshold stimuli. An action potential does not occur at 25 microamps, so it is called a threshold stimulus. If neuron is stimulated with a 50 microamp current, an action potential would occur, and it would be similar in size to the 25 microamp induced action potential. During the action potential, a second stimulus, no matter how strong, will not produce a second action potential because the membrane is in its absolute refractory period. This occurs because the voltage gated Na+ channeks are either already open or have proceeded to the inactivated state. Immediately after an action potential, some of the K+ voltage gated channels that repolarized the membrane are still open. During this time, a second action potential can be produced, but only if stimulus strength is larger than usual. This is the relative refractory period, which coincides roughly with the period of afterhyperpolarization. During this time, some of the voltage gated Na+ channels have returned to their closed state and could therefore open again

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