how do neurons communicate

The Human Nervous System

The human nervous system is made up of billions of interconnected neurons that communicate with one another through special chemical messengers. Each neuron is made up of a cell body and dendrites, which are where signals from other neurons are obtained. The obtained signals are then transmitted as electrical impulses through the axion. In the emitter field, the axon branches out to form synapses. At the synapse, electrical impulses from the axon are translated into chemical signals.

Synapses and Neuron Communication

The 'stuff' in the chemical signals then goes in one direction. If the other cell absorbs the transmission, one cell must communicate. The number of synapses varies in number from one neuron to the next ranging from as little as one in one neuron to as much as one hundred thousand in others. Synapses consist of the nerve ending of the presynaptic neuron; the postsynaptic neuron membrane that receives signals; and the synaptic cleft that separates the presynaptic and postsynaptic neurons (Banich & Compton, 2010).

Neurotransmitters and Calcium Channels

Presynaptic nerve endings contain neurotransmitters which are stored in vesicles. Neurotransmitters are signal molecules and are stored in the synaptic vesicles in a membrane enclosure. Calcium channels in the plasma membrane are activated by an electrical signal arriving at the nerve ending. Calcium ions from the outside then flow into the interior of the synapse through the channels.

Action Potential and Neuronal Communication

This movement of ions across the axon is responsible for the phenomenon referred to as action potential (Banich & Compton, 2010). Axion potential in turn occurs when a neuron sends information across an axon away from the cell bodies. It is due to a spike in electrical activity cause by a depolarizing current. A stimulus triggers the resting potential to spike when it reaches threshold. Failure to reach the threshold results in no the action potential not being triggered. During the action potential, a stimulus first triggers the opening of calcium channels. The relatively high number of calcium ions on the outside causes a rush of ions into the neuron and thus results in its depolarization. When the channels reopen, ions rush out of the neuron reversing the depolarization hence the neuron becomes repolarized and back to action potential from resting potential (Banich & Compton, 2010).

Neurotransmitter Release and Postsynaptic Response

The inflow of the calcium ions result in an encounter with a molecular machine situated between the vesicle membrane and the plasma membrane and the activation of the latter. The machine causes the membranes in the starting position to fuse with the plasma membrane resulting in a release of neurotransmitters into the synaptic cleft. On the postsynaptic side of the synaptic cleft, the docking sites on the membrane which regulate its electrical properties come into contact with the neurotransmitters. As a result, the membrane's electrical resistance is altered. The recipient cell processes the resulting electrical potential change rapidly (Banich & Compton, 2010).

Vesicle Recycling and Signal Transfer

The above process requires a lot of energy which is provided by the protein molecule proton ATPase which pumps protons to the vesicles and is facilitated by adenosine triphosphate (ATP). These proteins are also required for replenishing the synaptic vesicles membranes which are transported back to the nerve ending once membrane fusion occurs. The process become repeated in the life cycle of vesicles in the transfer of signals between neurons.

Reference

Banich, M. T., & Compton, R. (2010). Cognitive Neuroscience. Wadsworth.