ANATOMY

Detailed explanation-1: -The neurotransmitters are contained within small sacs called synaptic vesicles, and are released into the synaptic cleft by exocytosis.

Detailed explanation-2: -Influx of calcium ions into the presynaptic nerve terminal causes vesicles (loaded with neurotransmitters) migrate toward the presynaptic membrane. Then, the vesicle and membrane fuse, and neurotransmitter is released into the synaptic cleft by exocytosis.

Detailed explanation-3: -Neurons talk to each other across synapses. When an action potential reaches the presynaptic terminal, it causes neurotransmitter to be released from the neuron into the synaptic cleft, a 20–40nm gap between the presynaptic axon terminal and the postsynaptic dendrite (often a spine).

Detailed explanation-4: -Acetylcholine, for example, is the neurotransmitter that is released by a neuron to stimulate a muscle cell. If the axon terminal fails to release acetylcholine, there will be no chemical to activate the target muscle.