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Main component of the nervous system From Wikipedia, the free encyclopedia
Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain and spinal cord, and the peripheral nervous system (PNS) comprising the branching peripheral nerves. It is composed of neurons, also known as nerve cells, which receive and transmit impulses, and neuroglia, also known as glial cells or glia, which assist the propagation of the nerve impulse as well as provide nutrients to the neurons.[1]
| Nervous tissue | |
|---|---|
 Example of nervous tissue | |
 Cells of nervous tissue | |
| Identifiers | |
| MeSH | D009417 |
| Anatomical terminology | |
Nervous tissue is made up of different types of neurons, all of which have an axon. An axon is the long stem-like part of the cell that sends action potentials to the next cell. Bundles of axons make up the nerves in the PNS and tracts in the CNS.
Functions of the nervous system are sensory input, integration, control of muscles and glands, homeostasis, and mental activity.
Nervous tissue is composed of neurons, also called nerve cells, and neuroglial cells. Four types of neuroglia found in the CNS are astrocytes, microglial cells, ependymal cells, and oligodendrocytes. Two types of neuroglia found in the PNS are satellite glial cells and Schwann cells. In the central nervous system (CNS), the tissue types found are grey matter and white matter. The tissue is categorized by its neuronal and neuroglial components.[2]
Neurons are cells with specialized features that allow them to receive and facilitate nerve impulses, or action potentials, across their membrane to the next neuron.[3] They possess a large cell body (soma), with cell projections called dendrites and an axon. Dendrites are thin, branching projections that receive electrochemical signaling (neurotransmitters) to create a change in voltage in the cell. Axons are long projections that carry the action potential away from the cell body toward the next neuron. The bulb-like end of the axon, called the axon terminal, is separated from the dendrite of the following neuron by a small gap called a synaptic cleft. When the action potential travels to the axon terminal, neurotransmitters are released across the synapse and bind to the post-synaptic receptors, continuing the nerve impulse.[4]
Neurons are classified both functionally and structurally.
Functional classification:[5]
Structural classification:[5]
Neuroglia encompasses the non-neural cells in nervous tissue that provide various crucial supportive functions for neurons. They are smaller than neurons, and vary in structure according to their function.[4]
Neuroglial cells are classified as follows:[6]
In the central nervous system:[11]
In the peripheral nervous system:[12]
The three layers of connective tissue surrounding each nerve are:[11]
The function of nervous tissue is to form the communication network of the nervous system by conducting electric signals across tissue.[13] In the CNS, grey matter, which contains the synapses, is important for information processing. White matter, containing myelinated axons, connects and facilitates nerve impulse between grey matter areas in the CNS.[14] In the PNS, the ganglion tissue, containing the cell bodies and dendrites, contain relay points for nerve tissue impulses. The nerve tissue, containing myelinated axons bundles, carry action potential nerve impulses.[11]
Neoplasms (tumours) in nervous tissue include:
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