Where do neurotransmitters get released in chemical synapses?

• A. From dendrites in the postsynaptic neuron.
• B. From the synaptic vesicles in the presynaptic terminal.
• C. From the postsynaptic receptors on the membrane.
• D. From the presynaptic terminal's cytoplasm directly into the synaptic cleft.

Answer: (B)

In chemical synapses, neurotransmitters are released from synaptic vesicles located in the presynaptic terminal. When an action potential arrives, voltage-gated calcium channels open, calcium floods in, and this elevated Ca2+ triggers the vesicles to fuse with the presynaptic membrane and exocytose their contents into the synaptic cleft. The neurotransmitters then diffuse across the cleft and bind to receptors on the postsynaptic membrane, modulating ion channels or intracellular signaling.

Dendrites in the postsynaptic neuron are the receiving side, not the release site. Postsynaptic receptors are the targets that detect the neurotransmitter, not the source of release. Releasing directly from the presynaptic terminal’s cytoplasm into the cleft would bypass the vesicle system and the regulated exocytosis process that normally controls release.