Synapse: Definition & Transmission

Instructor: John Williams
Neurons are cells in the nervous system that are necessary to communicate with other bodily cells and systems. This communication is done through connection points known as synapses.


The nervous system is the primary coordination system in the body. It serves the purpose of directing the function of other organs, controlling processes within the body, and maintaining homeostasis (or balance). This is achieved by cells, called neurons, which serve as relay units for electrical signals used for cellular communication. These cells interact with each other and other tissues through a junction known as a synapse.

Structure of a Synapse

Neurons are cells that are excitable, or able to be stimulated electrically. This serves as the method by which these cells communicate with other cells. Electrical signals in a neuron are delivered to another cell via the axon, or transmitting structure.

Imagine whispering into someone's ear. While you may be very close to the person in order to deliver the message, chances are, you don't physically have to touch in order for the information to be passed. Neurons, in a similar manner, do not physically connect with the cells they stimulate. Rather, they communicate with each other through the release of neurotransmitters, or chemical messengers. These neurotransmitters are released from the end of the axon and diffuse across a small space to the target cell. Therefore, a synapse, which is the name of this communication region, consists of:

1) The axon terminal of a neuron

2) The space between the two cells, called a synaptic cleft

3) The receptors on the target cell that bind the neurotransmitters

Schematic of a Synapse

Receptors in the Synapse

Neurotransmitters are necessary for cell-to-cell communication. They bind to receptors on target cells in order to transmit the electrical signal. Receptors for neurotransmitters are specific for individual messenger types, and, therefore, the type of neurotransmitter released in a synapse will be determined by the type of receptors found.

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