BioMedical Admissions Test (BMAT) 2025 – 400 Free Practice Questions to Pass the Exam

The release of neurotransmitter molecules during synaptic transmission is primarily triggered by the presence of calcium ions. When an action potential arrives at the presynaptic terminal, it causes voltage-gated calcium channels to open. This allows calcium ions to flow into the neuron. The influx of calcium is crucial, as it initiates the processes that lead to the fusion of neurotransmitter-containing vesicles with the presynaptic membrane. As these vesicles fuse, they release their contents into the synaptic cleft, allowing neurotransmitters to bind to receptors on the postsynaptic membrane, thereby facilitating communication between neurons.

While a stimulus from an impulse is involved in initiating the action potential, it is the subsequent influx of calcium ions that directly triggers neurotransmitter release. Depletion of neurotransmitter vesicles refers to a state that occurs after repeated transmission and does not initiate the process. An increase in synaptic cleft width does not play a role in the triggering mechanism of neurotransmitter release.