Transmission at Synapse

Transmission at the Synapse: Mechanisms and Theories

Transmission of a nerve impulse across a synapse is one of the key processes in the nervous system, allowing information to be transmitted from one neuron to another. However, the mechanisms underlying this process are still not fully understood. In this article we will consider two main theories of synaptic transmission: electrical and chemical.

Electrical transmission theory implies that there is direct contact between neurons, allowing electrical current to pass from one neuron to another. Electron micrographs of synapses show that the membranes of the axon (sending neuron) and dendrite (receiving neuron) are very close, but no exact contact has been detected between them. There may be a gap of about 15 nm between them, but this does not exclude the possibility of effective "cable" communication at the synapse. This theory assumes that the transmission processes along the nerve fiber and through the synapse are fundamentally the same. However, there is a difference: all synapses conduct impulses in only one direction, while nerve fibers have the same conductivity in both directions.

The theory of chemical transmission, in turn, suggests that the physical separation of nerve fibers at the synapse prevents "cable" transmission, and a chemical mechanism comes into play instead. According to this theory, a specific substance called a transmitter is synthesized at the end of the axon. When a nerve impulse arrives, the transmitter is released and diffuses through the synaptic space. It then binds to receptors on the surface of the dendrite of a nearby neuron, causing changes in the membrane and depolarization, resulting in a new action potential. This potential then propagates along the neuron to the next synapse, where the process is repeated.

A wealth of evidence indicates that chemical transmission at the synapse is common. However, some researchers have discovered the electrical basis of transmission at specific synapses, such as the giant synapse of the ventral ganglion of the crayfish. In this case, the contact between the membranes acts as an electrical synapse, allowing current to pass without the need for chemical transmission.

Research into the mechanisms of transmission at synapses continues, and scientists are striving to understand the details of this complex process. Some questions that remain open include the mechanisms regulating transmitter release, the binding specificity between transmitter and receptors, and the role of other molecules such as neurotransmitters and neuromodulators in signal transduction at the synapse.

In conclusion, transmission at synapses is a complex mechanism that continues to attract research interest. The two main theories - electrical and chemical transmission - offer different explanations for this process. Although many synapses operate on the basis of chemical transmission, some special cases may use electrical transmission. Further research in this area will help us better understand the mechanisms of nerve impulse transmission at the synapse and their role in the functioning of the nervous system.