Nervous System: Neuron, Synapse, Reflexes · Zoology

What is the 'Absolute Refractory Period' of a neuron?

  1. The time when a neuron is at its resting potential and fully excitable
  2. The time when only an exceptionally strong stimulus can trigger a second action potential, because Na⁺ channels are partially recovered
  3. The time during which no action potential can be initiated, regardless of stimulus strength
  4. The time it takes for neurotransmitters to cross the synaptic cleft
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Correct answer: The time during which no action potential can be initiated, regardless of stimulus strength

The absolute refractory period occurs when voltage-gated Na⁺ channels are either already open or in their inactivated state. During this window no second action potential can be triggered no matter how strong the stimulus, ensuring action potentials are discrete, unidirectional events.

Difficulty: Medium Question 7 of 20

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