[Campbell Biology P.1127] Referring to the 'WHAT IF?' question in the text: If all Ca2+ ions ... | Practice Question

Referring to the 'WHAT IF?' question in the text: If all Ca2+ ions were removed from the fluid surrounding a neuron, how would this primarily affect synaptic transmission?

  • A: Neurotransmitter release from the presynaptic terminal would be significantly reduced or inhibited.
  • B: The action potential would fail to propagate along the axon.
  • C: Ligand-gated ion channels on the postsynaptic membrane would open spontaneously.
  • D: Synaptic vesicles would fuse more rapidly with the presynaptic membrane.

Explanation

The text and diagram clearly show that after depolarization, voltage-gated Ca2+ channels open, leading to an influx of Ca2+. This elevated Ca2+ concentration is what causes synaptic vesicles to fuse with the presynaptic membrane and release neurotransmitters. Therefore, without Ca2+, this crucial step of neurotransmitter release would be inhibited.