Functional Classification

The functional classification of synapses is based on the mode of impulse transmission. According to the function or physiology, synapses are of two types – electrical synapses and chemical synapses.

1. Electrical Synapse

In these synapses, there are gap junctions between the pre and postsynaptic membranes which allow the transmission of the depolarization wave directly from the pre to the postsynaptic membrane. Electrical synapses are faster than chemical synapses.

There is the direct exchange of ions between and the transmission of an electric signal across the electrical synapse is similar to the conduction of impulse in an axon. Because of this reason, the action potential reaches the end part of the presynaptic neuron directly into the postsynaptic neuron.

Due to the direct flow of current, synaptic delay is very less. Moreover, the impulse is transmitted in either direction through the electrical synapse. Electrical synapses are not as flexible as chemical synapses as they cannot turn the excitatory signal into the inhibitory signal.

This type of impulse transmission occurs in some tissues like the cardiac muscle fibers, smooth muscle fibers of the intestine, and the epithelial cells of the lens in the eye.

2. Chemical synapse

In these synapses, the transmission of signals occurs by releasing a ”chemical transmitter” from the presynaptic terminal into the synaptic cleft. Chemical synapses are more common. A chemical synapse is the junction between two nerve fibers or between a nerve fiber and a muscle fiber. There is a fluid-filled space between the two neurons called the synaptic cleft. The nerve impulse cannot jump from one neuron to another. Axon terminals have a knob-like structure, which contains synaptic vesicles.

There are molecules of such special types of proteins in the membrane of the postsynaptic synapse cells on the nucleus, which cause chemical stimulation of the nerve as soon as they bind to the molecules of the substance. As a result of this stimulation, the same changes take place in the cell membrane of the postsynaptic neuron cell which converts the resting phase potential to the action potential, that is, necessary for the generation of inspiration. 

Neurotransmitters bind to the receptors present in the postsynaptic membrane. This results in the opening of voltage-gated channels and the flow of ions. This causes a change in the polarization of the postsynaptic membrane and the electric signal is conducted across the synapse

Synapse – Definition, Parts, Types: A synapse is a small space between two neurons, where nerve impulses are relayed through a neurotransmitter from the axon of a presynaptic (to send information) neuron to the dendrite of a postsynaptic (receive Information ) neuron. The term “synaptic cleft” or “synaptic gap” refers to it. A synapse is a point of interaction where a neuron and another neuron or other cell join. Scientist Charles Sherrington coined the word “synapse” in 1897 from the Greek words “syn,” which means “together,” and “haptein,” which means “to hold.”

Synapse serve as junctions or relay centers where a nerve cell transfers its nerve information to nearby nerve cells. Neurons are cells that transfer information between your brain and other parts of the central nervous system and peripheral nervous system. The nerve cell carrying information at the synapsis is called presynaptic and the cell receiving information is called postsynaptic.