Neurotransmission

Neurotransmission (Latin: transmissio = passage, crossing; from transmitto = send, let through), also called synaptic transmission, is the process by which signaling molecules called neurotransmitters are released by a neuron (the presynaptic neuron), and bind to and activate the receptors of another neuron (the postsynaptic neuron). Neurotransmission usually takes place at a synapse, and occurs when an action potential is initiated in the presynaptic neuron. The binding of neurotransmitters to receptors in the postsynaptic neuron can trigger either short term changes, like changes in the membrane potential called postsynaptic potentials, or longer term changes by the activation of signaling cascades.

Nerve impulses are essential for the propagation of signals. These signals are sent to and from the central nervous system via efferent and afferent neurons in order to coordinate smooth, skeletal and cardiac muscles, bodily secretions and organ functions critical for the long-term survival of multicellular vertebrate organisms such as mammals.

Neurons form networks through which nerve impulses travel. Each neuron receives as many as 15,000 connections from other neurons. Except in the case of an electrical synapse through a gap junction, neurons do not touch each other, they have contact points called synapses. A neuron transports its information by way of a nerve impulse. When a nerve impulse arrives at the synapse, it releases neurotransmitters, which influence another cell, either in an inhibitory way or in an excitatory way. The next neuron may be connected to many more neurons, and if the total of excitatory influences is more than the inhibitory influences, it will also "fire", that is, it will create a new action potential at its axon hillock, in this way passing on the information to yet another next neuron, or resulting in an experience or an action.