When an action potential reaches the presynaptic membrane, it causes the opening of certain voltage-gated ion channels that permit the influx of specific ions, which causes synaptic vesicles to fuse with the presynaptic membrane and release their neurotransmitter substances via exocytosis into the synaptic cleft. These voltage-gated ion channels permit the A) influx of Na⁺ B) outflow of K⁺ C) influx of Cl - D) influx of Ca²⁺ E) outflow of Cl -

Question

Quizplus · Accepted Answer

Voltage-gated ion channels that permit the influx of specific ions are typically calcium channels, which allow the influx of Ca2+ ions. This influx of Ca2+ ions is what triggers synaptic vesicles to fuse with the presynaptic membrane and release their neurotransmitter substances into the synaptic cleft via exocytosis. Option A and B refer to the influx and outflow of sodium (Na+) and potassium (K+) ions, respectively, which are involved in generating the action potential but not in synaptic transmission. Option C refers to the influx of chloride (Cl-) ions, which can play a role in some inhibitory forms of synaptic transmission but is not necessary for all types of synaptic transmission. Option E refers to the outflow of chloride (Cl-) ions, which is also not necessary for synaptic transmission.

When an Action Potential Reaches the Presynaptic Membrane, It Causes