Final answer:
Neurotransmitters are released from the axon terminal, also known as the synaptic end bulb, of a neuron. The release occurs when calcium ions enter the terminal via voltage-gated calcium channels, leading to the fusion of neurotransmitter vesicles with the presynaptic membrane and subsequent neurotransmitter release into the synaptic cleft.
Step-by-step explanation:
The part of the neuron where neurotransmitters are released is known as the axon terminal or synaptic end bulb. During neurotransmission, an electrical signal known as an action potential travels down the axon to the axon terminal. Here, the arrival of the action potential triggers the opening of voltage-gated calcium channels, allowing calcium ions (Ca²⁺) to enter the axon terminal. This increase in Ca²⁺ concentration inside the terminal causes synaptic vesicles filled with neurotransmitters to merge with the presynaptic membrane, a process called exocytosis. As a result, neurotransmitters are released into the synaptic cleft, the small gap between the presynaptic neuron and the postsynaptic target cell. Within the synaptic cleft, neurotransmitters bind with specific receptors on the postsynaptic cell, enabling the continuation of the signal.