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===Glial Cells===

===Glial Cells===

Glial cells make up approximately 50% of the volume of the nervous system and the number of glial cells out-numbers the nerve cells by a factor of ten to one. The primary function of glial cell is to provide support to the neuronal cells. There are several different types of glial-style cell; in the PNS these are referred to as '''Schwann cell''' whilst in the CNS they are referred to as '''Oligodendrocytes'''.  

Glial cells make up approximately 50% of the volume of the nervous system and the number of glial cells out-numbers the nerve cells by a factor of ten to one. The primary function of glial cell is to provide support to the neuronal cells. There are several different types of glial-style cell; in the PNS these are referred to as '''Schwann cells''' and whilst in the CNS they are referred to as '''Oligodendrocytes'''.  

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[[Image:oligodendrocyte.jpg|thumb|right|100px|Oligodendrocyte]]

[[Image:oligodendrocyte.jpg|thumb|right|100px|Oligodendrocyte]]

The term "oligodendrocyte" literally means a "cell with many branches". Oligodendrocyte precursors are found throughout the CNS and these precursors are post-mitotic, meaning oligodendrocytes can be replaced. Oligodendrocytes can [[PNS Structure - Anatomy & Physiology#The Process of Myelination|myelinate]] up to 40 axons at a time. The myelin sheath formed by oligodendrocytes has numerous functions including; decreasing any ion leakage from the axon lowering the capacitance of the cell membrane and increasing impulse speed along the axon by allowing saltatory conduction of action potentials between the nodes of Ranvier.

The term "oligodendrocyte" literally means a "cell with many branches". Oligodendrocyte precursors are found throughout the CNS and these precursors are post-mitotic, meaning oligodendrocytes can be replaced. Oligodendrocytes can [[PNS Structure - Anatomy & Physiology#The Process of Myelination|myelinate]] up to 40 axons at a time. The myelin sheath formed by oligodendrocytes has numerous functions including; decreasing any ion leakage from the axon lowering the capacitance of the cell membrane and increasing impulse speed along the axon by allowing saltatory conduction of action potentials between the nodes of Ranvier.

===Nerve Impulse Propagation===

===Nerve Impulse Propagation===

Nerves are able to create, amplify and propogate electrical impulses that run along their axon. These nerve impulses are a form of action potential that is carried by ions. The nerve impulse is in effect an electrical difference between the inside and outside of the axon and is caused by ion movements across the membrane. Nerve impulses can occur from a number of sources including sensiry cells, action potentials from other connected nerves or spontaneous depolarisation of the nerve cell membrane.

Nerves are able to create, amplify and propogate electrical impulses that run along their axon. These nerve impulses are a form of action potential that is carried by ions. The nerve impulse is in effect an electrical difference between the inside and outside of the axon and is caused by ion movements across the membrane. Nerve impulses can occur from a number of sources including sensiry cells, action potentials from other connected nerves or spontaneous depolarisation of the nerve cell membrane.