The term Neuron comes from the Greek word neyron (nerve); It is a cell of the nervous system specialized in capturing stimuli from the environment and in transporting and transmitting nerve impulses (electrical messages). The neuron is considered the basic nervous unit, both functional and structural, of the nervous system. The neuron does not divide, nor does it reproduce. Their number remains fixed from birth, and from a certain age a large number of them are lost. The size and shape of neurons is highly variable, but they all fulfill their function of conducting nerve impulses. A neuron is made up of a cell body or soma, is the widest part of it and contains a nucleus surrounded by cytoplasm. There are also extensions or fibers known as dendrites and axons. The former are short and numerous branches that lead the impulse to the cell body; and the second is a long branch that transmits said impulse from the cell body to the nearby neuron.
The connection between two neurons is called a synapse . This originates between the terminal button of an axon and the initial dendrites of another neuron. As is well known, its basic function is to transmit messages in nerve impulses through a process that can be electrical (when an impulse travels along a nerve fiber), and chemical (when the signal is transmitted from one neuron to another), both types involve certain substances called neurotransmitters.
Once the neuron has been excited and has conducted a nerve impulse, it will not be projected again until after a certain time, designated as the absolute refractory period , after which time the relative refractory period begins, where the neuron needs an excitation greater than the usual one to unload an impulse.
According to its function, the neuron is classified into three types: a) sensitive or afferent, which captures stimuli and conducts impulses to the brain or spinal cord, is located in the sense organs; b) motor or efferent, this is in charge of conducting the responses from the brain or spinal cord to the muscles or glands; and c) associative or interneuron, links the sensory and motor neurons, is located in the spinal cord and in the brain.
