noun, singular: axon terminal
Axon terminals refer to the axon endings that are somewhat enlarged and often club- or button-shaped. Axon terminals are that part of a nerve cell that make synaptic connections with another nerve cell or with an effector cell (e.g. muscle cell or gland cell).
Axon terminals contain various neurotransmitters and release them at the synapse. These neurotransmitters transmit electrical impulses to the target cell (neuron or effector) and the neuron that releases these neurotransmitters via the axon terminals is called a presynaptic neuron whereas the neuron that receives the impulse is called a postsynaptic neuron. The transmission of nerve impulse begins with an action potential traveling along the membrane of the presynaptic neuron until the synapse. Electrical depolarization of the membrane at the synapse will lead to increased permeability to calcium ions. Influx of calcium ions activates calcium-sensitive proteins into releasing the neurotransmitters into the synaptic cleft. These neurotransmitters bind to the receptor molecules on the membrane of the postsynaptic neuron, activating the latter. The neurotransmitters eventually break loose and may either be reabsorbed by the presynaptic neuron or broken down metabolically.