Synaptic transmission
MCAT glossary · Psychological, Social & Biological Foundations of Behavior
Definition
AP triggers Ca^2⁺ influx at axon terminal → vesicle fusion → neurotransmitter release → postsynaptic receptor binding → EPSP or IPSP.
Synaptic transmission in plain English
This is how one nerve cell talks to the next across the tiny gap between them. An electrical signal (the action potential, or "AP") races down the sending neuron and triggers calcium to rush in at the tip; that calcium makes little bubbles (vesicles) full of chemical messengers dump their contents into the gap. Those messengers, called neurotransmitters, float across and plug into receptors on the next cell — like a key fitting a lock — either nudging it to fire (an excitatory signal, EPSP) or telling it to quiet down (an inhibitory signal, IPSP). So the message starts electrical, briefly turns chemical to cross the gap, then becomes electrical again — a relay race where the baton switches form mid-handoff.
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