This is an extract of our Neuronal Tissue And Peripheral Nerve Structure document, which we sell as part of our Neuroscience 1 Notes collection written by the top tier of University Of Nottingham students.
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Neuronal Tissue and Peripheral Nerve Structure Neurons Neurons are one type of cell that makes up neural tissue. They are highly specialised cells, and when fully mature lack the property of cell division. They do however have a limited ability to regenerate processes in the PNS. Neurons are large cells that consist of a cell body, also called a perikaryon, and several processes extending out of the perikaryon. One of these processes will always be an axon, whilst the rest are dendrites. The cell body has a large nucleus and nucleolus for production of ribosomes, and large amounts of endoplasmic reticulum, which contain Nissl substance. There is also a prominent Golgi body. This signs show that neurons are active protein producing cells. Each neuron may have several dendrites that branch in a tree-like manner, and will contain Nissl substance. Dendrites are a cytoplasm-like extension of the cell body, and are the receptive area for impulse transmission. However, each neuron has only one axon that is without Nissl substance and emerges from the axon hillock, also without Nissl substance, and is surrounded by Schwann cells. The axon is responsible for transmission of nerve impulses away from the cell body. The axon remains unbranched until it reaches its axon terminal. Multipolar neurons are those with one axon and multiple dendrites. Groups of such neurons located in the CNS are called nuclei. Pseudounipolar neurons have one process that leaves the cell body and quickly divides into two. Structurally, both processes resemble axons, but only one functionally acts as an axon. Unipolar neurons are often general sensory neurones. The cell bodies of unipolar neurons are often grouped together in ganglia in the PNS. Bipolar neurons have two processes, one at each end. One is a dendritic, whilst the other is the axon. Afferent or sensory neurons convey information towards the CNS. Efferent or motor neurons convey information away from the CNS. Association or interneurons connect or associate one point in the CNS with another but never leave the CNS. They may bridge between sensory and motor neurons. Neurotransmitters and proteins are synthesied in the cell body, in Nissl bodies, and transported via either: the axoplasmic flow - contractions that push the cytoplasm from the axon hillock to nerve endings; or the axonal forward/retrograde transport via neurotubules and kinesins. Nerves A nerve is composed of several bundles of nerve axons (called nerve fibres) held together by connective tissue. Most nerves contain sensory and motor fibres.
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