PATHOLOGY

Detailed explanation-1: -When the action potential reaches the nerve terminal, voltage-dependent Ca2+ channels open and Ca2+ rushes into the neuron terminal due to a greater extracellular concentration. Ca2+ channels appear to be localized near the active zones of the vesicular membrane.

Detailed explanation-2: -An action potential (AP) arriving at the axon terminal membrane opens voltage-gated calcium channels in the membrane, which let calcium go in and initiate a membrane fusion reaction with synaptic vesicles, and release glutamate into the synaptic cleft.

Detailed explanation-3: -The open calcium channels allow calcium to diffuse into the synaptic terminal. This calcium influx causes synaptic vesicles to fuse with the presynaptic membrane. The content of these vesicles-acetylcholine-is then released into the synaptic cleft. Although this process consists of many steps, it happens quickly.

Detailed explanation-4: -When the presynaptic membrane is depolarized, voltage-gated Ca2+ channels open and allow Ca2+ to enter the cell. The calcium entry causes synaptic vesicles to fuse with the membrane and release neurotransmitter molecules into the synaptic cleft.