Nervous tissue

the structure of a neuron
The structure of a neuron: 1 - the body of a neuron; 2 - dendrites; 3 - axon; 4 - axon collaterals; 5 - myelin sheath of nerve fibers; 6 - terminal branching nerve fibers. The arrows show the direction of propagation of the nerve impulses (Polyakov).

Nerve tissue is one of the tissues of the body performing the functions of perception and irritation of nerve impulses. Structural elements of the nervous tissue are nerve cells, or neurons (Fig.), and neuroglia (see). Each neuron consists of a body processes; dendrites and axons. According to the number of processes distinguish unipolar (odnorodnye), bipolar (dortrecht) and multipolar (mnogochastichnye) neurons. Some processes of conduct nerve impulses to the cell (dendrites), others - from cell (the axon). On the functional characteristics distinguish afferent (sensitive), associative (inset) and efferent (motor) neurons. The body of the neuron is its trophic centre, violation of integrity which leads to cell death. The body consists of a nucleus and cytoplasm (necroplasma). In necroplasma, besides the usual organelles contain special organelles - neurofibrillar and substance Nissle (thyroid). Neurofibrillar - thin filaments, located in different areas and forms a dense network; they consist of very thin (70-200 a) protofibril. Neurofibrillar are supporting the skeleton of a neuron. Thyroid represents glybki basophilic substances, which are located around the nucleus, and calling at the base of the dendrites. Thyroid takes part in the processes of synthesis of substances necessary for maintaining the structural integrity of the neuron and its specific function. Synthetic substances continuously transported from the body of a neuron in his fingers. The process of neuron is called the nervous fibers. Every fiber consists of an axial cylinder (axon), which are located inside axoplasm, neurofibrillar, mitochondria and synaptic vesicles. Depending on the structure of membranes enveloping axons, there are makunia (myelin) and bezmaterny fiber. Bezmarochnoj fiber consists of 7-12 thin axons, which are within the band, formed by a chain neuroglial cells. Each axon is separated from the cytoplasm of glial cells her own shell. Makoto fiber consists of one more Tolstoy axon, which, in addition to glial plates, shrouded in the myelin sheath. Due to the presence of Makoto shell and its segmented structure significantly increases the speed of a nerve impulse. Peripheral branching fibers form the nerve endings. Depending on the functions of these endings are divided into receptor (sensitive) and effectslotensin (motor). Receptors are encapsulated and non-encapsulated. First separated from other connective tissues capsules (calf of Vater - Pacini, Meissner, Krause's bulbs and other), the second direct contact with innervated fabrics. Effector end formed by branching axons motor cells. On striated muscle fibres motor fibers form the nerve endings - the so-called motor plaques. The end of the axon of one neuron body and other processes called internationallym the synapse (see).