What constitutes the basic structure of a chemical synapse?

• A. A synapse consists of a presynaptic terminal, neurotransmitters released directly into the bloodstream.
• B. A synapse includes a synaptic terminal, synaptic vesicles, postsynaptic receptors, and a synaptic cleft.
• C. A synapse is a gap junction that directly passes ions between cells.
• D. A synapse has no vesicles.

Answer: (B)

Chemical synapses are built around a presynaptic terminal packed with synaptic vesicles that store neurotransmitters, a narrow gap called the synaptic cleft, and receptors on the postsynaptic membrane. When an action potential reaches the terminal, neurotransmitters are released from these vesicles into the cleft by exocytosis, diffuse across the gap, and bind to receptors on the postsynaptic cell to trigger a response. This arrangement enables precise chemical communication between neurons.

Releasing neurotransmitters into the bloodstream would be endocrine signaling, not a synapse. A gap junction, by contrast, is an electrical connection where ions pass directly between cells, not a chemical signaling across a cleft. And a synapse without vesicles wouldn’t support the vesicular release mechanism that is essential for chemical transmission.