PHYSIOLOGY
SYNAPTIC PHYSIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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an action potential will be initiated and proceed only back toward the axon hillock.
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two action potentials will be initiated, one going toward the axon terminal and one going back toward the axon hillock.
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no action potential will be initiated
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an action potential will be initiated, but it will die out before it reaches the axon terminal.
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Detailed explanation-1: -So, the correct option is ‘brief refractory period prevents a depolarization from occurring in the direction from which the impulse came’.
Detailed explanation-2: -Normally, action potentials spread only in one direction–from the axon hillock toward the axon terminus. At any given point along the way, the “upstream” sodium channels are in their refractory period, preventing the depolarization from sweeping back toward the axon hillock.
Detailed explanation-3: -But action potentials move in one direction. This is achieved because the sodium channels have a refractory period following activation, during which they cannot open again. This ensures that the action potential is propagated in a specific direction along the axon.
Detailed explanation-4: -Second, the action potential can only travel in one direction – from the cell body towards the axon terminal – because a patch of membrane that has just undergone one action potential is in a “refractory period” and cannot undergo another.
Detailed explanation-5: -The action potential moves down the axon beginning at the axon hillock. The action potential moving down a myelinated axon will jump from one Node of Ranvier to the next. This saltatory conduction leads to faster propagation speeds than when no myelin in present.