Definition of Synaptic Cleft

The synaptic cleft is a narrow gap that exists between the terminal button of a neuron (also known as the presynaptic neuron) and the dendrites of the neighboring neuron (known as the postsynaptic neuron) or an effector cell. It is a crucial component of the synapse—the junction where communication occurs between two adjacent neurons or a neuron and an effector cell.


The synaptic cleft is a fluid-filled space that measures approximately 20-40 nanometers in width. It separates the presynaptic and postsynaptic membranes, preventing direct contact between them. The presynaptic membrane refers to the membrane of the sending neuron, while the postsynaptic membrane represents the membrane of the receiving neuron or effector cell.


The primary function of the synaptic cleft is to ensure the unidirectional transmission of signals between neurons or from neurons to effector cells. It acts as a physical and chemical barrier that helps regulate the information flow. Neurotransmitter molecules, responsible for transmitting signals across the synapse, are released from the presynaptic terminal button into the synaptic cleft and then bind to receptors on the postsynaptic membrane, effectively initiating signal transmission.

Transmission of Signals

The synaptic cleft plays a vital role in signal transmission. When an action potential reaches the presynaptic terminal button, depolarization triggers the release of neurotransmitter molecules from vesicles located within the presynaptic neuron. These neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane. This binding leads to the generation of postsynaptic potentials, which can either be excitatory or inhibitory, thereby influencing the likelihood of an action potential being generated in the postsynaptic neuron.

Reuptake of Neurotransmitters

The synaptic cleft is also involved in the reuptake of neurotransmitter molecules. After signal transmission, excess neurotransmitters in the synaptic cleft need to be cleared to terminate the signal and allow for the initiation of new signals. Certain enzymes break down neurotransmitters, while others are taken back up into the presynaptic neuron through a process called reuptake. This recycling of neurotransmitters ensures the synaptic cleft is prepared for subsequent transmissions.


The synaptic cleft acts as a crucial interface in the communication between neurons and effector cells. Its structure and function enable precise and regulated signal transmission, providing a mechanism for efficient transmission and integration of information within the nervous system.