Composition and functions of blood
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Nervous tissue is responsible for transmission of nervous impulses. It is built of two kinds of cells – neurons and glial cells.
Neurons are the main type of nervous tissue, they are responsible for transmission of nervous impulses mentioned above. They consist of the cell body and two kinds of outgrowths – dendrites and neurites (so-called axons).
Dendrites lead nervous impulses to the cell body, they are short and tree-shaped.
Neurites transmit nervous impulses from the cell body – further, to the next cell. They are covered with two sheaths – the internal part is called myelin sheath, and the external layer is called cell sheath. We should add, that the internal layer is a perfect isolator, which helps nervous impulses move much faster.
The sheaths are built of cells, that is why there are some nodes between them. They are called nodes of Ranvier.
Transmission of nervous impulses takes place through joints called synapses. They are placed between the axon of one cell and the dendrite of the next one. Nervous impulses are transmitted through synaptic vesicles, a substance called synaptic mediator goes through them.
Synapses (intercellular joints, that nervous impulses move through) are placed not only between nervous cells. There also are joints between nervous cells and muscular cells and glands.
Nervous tissue has very limited regeneration abilities. That is why, after severe accidents, the body can be permanently paralyzed.