Myelin is formed by cells wrapping themselves around the nerve axon. Whilst neurones have many dendrites, most cells only have one axon.Įach axon is coated in myelin – a layer of insulating lipid. The axon is a long, thin structure down which action potentials (the nerve impulse) are conducted.
They extend outwards, receiving input from the environment and from other neurones. The dendrites are elongated portions of the cell body. In the CNS, this is known as a nucleus, and in the PNS as a ganglion. In the nervous system, many neuronal cell bodies can group together to form a distinct structure. It is the site of protein synthesis, which occurs on small granules of rough endoplasmic reticulum called nissl substance. They all contain the same key structural components – the cell body, dendrites, the axon and the axon terminals. There are several different types of neurones found in the nervous system.
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