Neurotransmitters are endogenous, meaning proceeding from within, chemicals which relay, amplify, and modulate signals between a neuron , or an excitably cell in the nervous system, and another cell.

The nervous system is a network of specialized cells that communicate information about an organism’s surroundings and itself. It is composed of neurons and glial cells, that aid in the function of neurons.

The central nervous system is made up of the nerve cord, spinal cord, and the brain.

Neurotransmitters are packaged into synaptic vesicles that cluster beneath the membrane on the presynaptic side of a synapse and are released into the synaptic cleft, where they bind to receptors in the membrane on the postsynaptic side of the synapse.

A synapse is a specialized junction through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands.

Release of neurotransmitters usually follows arrival of an action potential, or nerve impulse, at the synapse, but may follow graded electrical potentials.