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synapse
(sinŽaps)
the junction between the processes of two neurons or between a neuron and an effector organ, where neural impulses are transmitted by chemical means. The impulse causes the release of a neurotransmitter (such as acetylcholine or norepinephrine) from the presynaptic membrane of the axon terminal. The neurotransmitter molecules diffuse across the synaptic cleft and bind with specific receptors on the postsynaptic membrane, causing depolarization or hyperpolarization of the postsynaptic cell.
Diagram of three synapses. Nerve impulse is indicated by arrows, showing that the direction of passage is from the terminal
arborization (TA) or nerve endings of the axon of one neuron to the dendrites (D) of another neuron.
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