Which feature distinguishes an electrical synapse from a chemical synapse?

• A Presence of a definite synaptic delay of about 0.5 ms
• B The postsynaptic response is always inhibitory
• C Transmission occurs through gap junctions and can be bidirectional ✓
• D It is the predominant type of synapse in the adult mammalian cerebral cortex

Explanation

Electrical synapses are formed by connexon hemichannels forming gap junctions that allow direct ion flow between cells. Current can pass in either direction, transmission is nearly instantaneous with no synaptic delay, and the signal is usually, though not always, bidirectional. Chemical synapses show a delay of roughly 0.5 ms due to transmitter release and diffusion. Electrical synapses are common in cardiac muscle, smooth muscle, and developing neurons, but chemical synapses dominate the adult cortex.

Reference: Ganong's Review of Medical Physiology, 27th ed.

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