Neurophysiology and Synapses · USMLE Step 1

What is the main mechanism by which neurotransmitter action is terminated in the synaptic cleft?

  1. Spontaneous degradation within the postsynaptic receptor
  2. Diffusion, reuptake by neurons or glia, and enzymatic breakdown
  3. Closing of postsynaptic voltage-gated channels
  4. Continuous exocytosis of vesicles
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Correct answer: Diffusion, reuptake by neurons or glia, and enzymatic breakdown

Signal termination typically involves removal of neurotransmitter from the cleft by diffusion, uptake by presynaptic neuron or glial cells, and/or enzymatic degradation — not by receptors degrading the transmitter.

Difficulty: Medium Question 16 of 28

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