[Campbell Biology P.1127] What is the correct sequence of events during synaptic transmission... | Practice Question

What is the correct sequence of events during synaptic transmission at a chemical synapse, as described and illustrated in Figure 48.16?

  • A: Action potential arrives → Depolarization opens voltage-gated Ca2+ channels → Elevated Ca2+ causes vesicle fusion → Neurotransmitter binds to ligand-gated ion channels.
  • B: Neurotransmitter binds → Action potential arrives → Depolarization opens voltage-gated Ca2+ channels → Elevated Ca2+ causes vesicle fusion.
  • C: Elevated Ca2+ causes vesicle fusion → Neurotransmitter binds → Action potential arrives → Depolarization opens voltage-gated Ca2+ channels.
  • D: Depolarization opens voltage-gated Ca2+ channels → Action potential arrives → Elevated Ca2+ causes vesicle fusion → Neurotransmitter binds.

Explanation

Figure 48.16 and its accompanying text describe the precise sequence of events: 1 An action potential arrives, depolarizing the presynaptic membrane. 2 This depolarization opens voltage-gated Ca2+ channels, leading to Ca2+ influx. 3 The elevated Ca2+ concentration causes synaptic vesicles to fuse and release neurotransmitters. 4 The neurotransmitter then binds to ligand-gated ion channels on the postsynaptic membrane.