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Specialized nerve cells of multicellular organisms have initially evolved from one cell eukaryotes, in which there are every four stages of information flow within a single cell, as in today's bacteria and mobile protists. On the contrary; The anatomy of specialized nerve cells (neurons) in multicellular animals often reflect their particular role in the control of arousal, transmission, processing, and response. Regardless of the views, all neurons have the same functional organization, andit gives them the ability to collect information (either directly from the environment (as a sensory cell) or from other neurons or both) and to transfer it to other neurons, muscle cells, and target cells such as secretory cells. 

A typical nerve cell includes an enlarged cell body in which the nucleus is contained, and one or more extension or nerve fibers. Dendrites, which usually receive the information, are the axons in which the fibers are transmitted to the other cells. Specialized end-ends at the end of the axons transfer the signals to the dendrites of the target cells. In vertebrates, dendrites usually bind to the cell body, while in invertebrates, the axon is usually directly related to dendrites. Thus, the cell body is left out of the information flow path. Most of the neural processes occur on these finger-like dendrites and on the cell body (in vertebrates). Dendrites are usually short and present in large numbers. They may be receiving signals from thousands of other cells. Many dendrites have multiple branches and have a fringed appearance. If stained and examined in the light microscope, they are found in the cytoplasm of a large amount of dark-colored material (Nissi body).
If examined in the electron microscope, they appear to be a comprehensive, flattened endoplasmic reticulum cistern network and a plurality of ribosomes associated therewith.
In contrast to the large number of dendrites, each neuron usually has an axon, which is usually longer and thicker than the dendrites. Although it has a large number of branches, it does not have a reticulated image and does not contain Nissi bodies. These histological differences reflect the fundamental functional difference between the dendrites taking information from other cells and the axons that transmit it to other cells. In the recent past, however, the situation was somewhat more complex.
Dendrites sometimes establish synapses with other dendrites, while axons sometimes make synapses, especially at the beginning and end ends. As we will see later, these synapses are extremely important in the processing of information in the nervous system.
In the central nervous system (CNS) of the vertebrates, neurons are in close contact with a large number of cells called neuroglia (or glia in short). The glia cells in the brain contain about 10 times the cranial volume and 10 times the number of neurons. Some glia cells provide nutrients to neurons and help protect a homogeneous environment by absorbing substances that are secreted by neurons. Most of these absorbed substances are returned to them for reuse of neurons. In at least some regions of the CNS, glia cells form pathways in which neurons migrate during development and elongate axons to achieve their targets.
Some glia cells called astrocytes can chemically communicate with each other. For this, long distances; however, they may transmit messages more slowly than electrical transmission in neurons. The role of this communication in the nervous system is not known.
A type of glia found in vertebrates and forming myelin is particularly well understood. The membrane of these specialized cells creates a myelin sheath containing dense lipid by repeatedly wrapping around the axon of many neurons in the CNS. This myelin sheath prevents aks cross talk on between the adjacent isolation and the adjacent axons. Many vertebrate axons in the periphery of the CNS are encapsulated with myelin sheaths, which are formed by cells called the Schwann cells that originate from the neural hill and are exactly the same as those made by glia cells in the CNS. Myelin sheaths reduce the area of ​​the neuronal membrane that da needs to be charged ik (thus reducing the metabolic expenditure associated with it) and axons increase the transmission rate of the impulse.
Source: poxox blogs

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