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Neurons - Anatomy & Physiology (view source)
Revision as of 15:58, 24 August 2011
, 15:58, 24 August 2011→Glial Cell/Schwann Cell
===Axon (Nerve Fibre)===
===Axon (Nerve Fibre)===
The axon is a very fine projection that can measure up to thousands of time the soma diameter in length. The axon carries nerve signals away from the soma. The structure and function of the axon is very similar between the CNS and the PNS. This has been covered in detail within the PNS Structure and Anatomy page so for further information please click [[PNS_Structure_-_Anatomy_%26_Physiology#Structure|here]].
The axon is a very fine projection that can measure up to thousands of time the soma diameter in length. The axon carries nerve signals away from the soma. The structure and function of the axon is very similar between the CNS and the PNS. This has been covered in detail within the PNS Structure and Anatomy page so for further information please click [[PNS_Structure_-_Anatomy_%26_Physiology#Structure|here]].
===Glial Cell/Schwann Cell===
===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'''. Details regarding the Schwann cell have been covered within the PNS Structure and Anatomy page so for further information regarding Schwann cells please click [[PNS_Structure_-_Anatomy_%26_Physiology#The_Schwann_Cell|here]].
Details regarding the Schwann cell have been covered within the PNS Structure and Anatomy pag so for further information regarding Schwann cells please click [[PNS_Structure_-_Anatomy_%26_Physiology#The_Schwann_Cell|here]].
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Glial cells form a protective networked layer around the neuron within the CNS and also help to maintain the fluid content of the tissue surrounding the nerve. This protective layer is referred to as the '''myelin sheath''' and axons that are wrapped within this myelin sheath are able to conduct nerve impulses at higher speeds than those that are not wrapped. During foetal development the glial cells wrap around axons numerous times and as the glial cell matures it looses the majority of it's cytoplasm. The remaining cellular structure consists of many layers of tightly packed lipid membranes around the axon.
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Periodically along the surface of the wrapped glial cell there are gaps approximately every 1-2mm. Each gap allows the environment external to the myelin sheath to be exposed to the axon for approximately 1-2υm. These gaps in the sheath are called the '''Nodes of Ranvier''' and are important in the conduction of impulses along the axon.
==Astrocytes==
==Astrocytes==