Multiple Choice
Which structures on the axon serve as the sites where action potentials 'jump' during saltatory conduction?
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45. Nervous System
Neurons and Action Potentials
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Which phase of the action potential is characterized by a rapid influx of Na$^+$ ions, resulting in a sharp rise in membrane potential?
A
Repolarization
B
Resting potential
C
Depolarization
D
Hyperpolarization
Verified step by step guidance1
Understand the concept of an action potential: It is a rapid change in the membrane potential of a neuron or muscle cell, which occurs in distinct phases including depolarization, repolarization, and hyperpolarization.
Identify the role of Na$^+$ ions during depolarization: During this phase, voltage-gated sodium channels open, allowing Na$^+$ ions to flow into the cell down their electrochemical gradient.
Recognize the effect of Na$^+$ influx: The rapid entry of positively charged Na$^+$ ions causes the inside of the cell to become less negative, leading to a sharp rise in membrane potential.
Compare depolarization with other phases: Depolarization is distinct from repolarization (where K$^+$ ions exit the cell to restore resting potential) and hyperpolarization (where the membrane potential becomes more negative than the resting potential).
Conclude that depolarization is the phase characterized by the rapid influx of Na$^+$ ions, resulting in a sharp rise in membrane potential.
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