Nervous System: Neuron, Synapse, Reflexes · Zoology

What happens during the hyperpolarization (undershoot) phase of an action potential?

  1. Sodium channels open widely, flooding the cell with Na⁺
  2. Potassium channels stay open, letting K⁺ continue to leave
  3. The Na⁺/K⁺ pump reverses direction and rapidly pushes ions back to resting levels
  4. Calcium ions rush in through voltage-gated channels to stabilize the membrane potential
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Correct answer: Potassium channels stay open, letting K⁺ continue to leave

Voltage-gated K⁺ channels are relatively slow to close. This leads to an excessive loss of positive ions, making the membrane potential even more negative than the resting state for a short period — the undershoot (hyperpolarization) phase.

Difficulty: Medium Question 14 of 20

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