All movements of muscles, work of internals and blood vessels are under control of nervous system. It transfers impulses from the central nervous system to peripheral. The basis of nervous system is formed by nervous tissue. What is represented by this structure?
Nervous tissue is the highly specialized fabric consisting of neurons (neurotsit) and a neuroglia (auxiliary cages). It develops from a nervous tube and 2 gangliozny plates and forms bodies of the central and peripheral nervous system. Nervous cages perceive irritation, further pass in a condition of excitement, develop and transfer impulses. Cages of a neuroglia fill intervals between neurotsit and provide their activity, that is performs basic, protective, sekretorny functions and also participates in process of a metabolism between neurons and blood vessels.
The neuron consists of a body of a star-shaped, polygonal or oval form and the shoots departing from it. As a rule, neurotsita have one or two long thin shoots (axon) and several thick and short (dendrites). Dendrites strongly branch and are close from a cage body. They perceive and transfer excitement to a neurotsit. The axon, with the branches departing from it, transfers excitement from one neuron to another, or the impulse on it goes to cells of other fabrics. Long shoots form nervous fibers.
Some congestions of axons are covered with fat-containing education which carries the name of a myelin cover. This a multilayered covering increases diameter of fiber and gives it white color. White substance of a head and spinal cord consists of myelin fibers. Nervous fibers without such covering have gray color. The main functions of nervous tissue are perception, processing and information transfer. Neurons transfer an impulse each other in places of contact of two neurotsit – synapses, by means of neurotransmitters. The transferring neuron excretes a neurotransmitter in a synapse, and accepting catches it and turns into an electric impulse. The nervous terminations react to various irritants: mechanical, chemical, electric and thermal. But all of them have to be a certain force and work rather long time. Distinctive property of nervous tissue – new neurons during life of an organism are not formed.