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====Anterograde Transport====

====Anterograde Transport====

Two basic forms of anterograde transport can be recognised: '''fast anterograde transport''' and '''slow anterograde transport'''. Fast anterograde transport allows movement of all membranous organelles such as synaptic vesicles and occurs at a rate of around 400mm/day (recent evidence suggests that there are many form of fast anterograde transport, mediated by different kinesins). Fast anterograde transport depends critically on oxidative metabolism, and is, in fact independent of the cell body. The "motor" molecule is an ATPase called '''kinesin'''. '''Slow anterograde transport''' deals with cytoskeletal elements and large soluble proteins. Slow anterograde transport can be further sub-divided into a slow component, which occurs at about 2mm/day (neurofilament, rubulin, actin) and a fast component, which occurs at around 4 mm/day, transporting all other proteins (eg myosin, clathrin).

Anterograde transport moves substances from the cell body to the axon. Two basic forms of anterograde transport can be recognised: '''fast anterograde transport''' and '''slow anterograde transport'''. Fast anterograde transport allows movement of all membranous organelles such as synaptic vesicles and occurs at a rate of around 400mm/day (recent evidence suggests that there are many form of fast anterograde transport, mediated by different kinesins). Fast anterograde transport depends critically on oxidative metabolism, and is, in fact independent of the cell body. Microtubules act as a static track along which the organelles can move, driven by the ATPase '''kinesin''' which acts as a "motor" molecule. Fast anterograde transport is independent of the cell body. Anything which interfers with with energy supply or cytoskeleton necessary for fast anterograde transport has profound effects on the health of the axon. Agents such as colchicine or vincristine block microtubule assembly, disrupting fast anterograde transport.'''Slow anterograde transport''' deals with cytoskeletal elements and large soluble proteins. Slow anterograde transport can be further sub-divided into a slow component, which occurs at about 2mm/day (neurofilament, rubulin, actin) and a fast component, which occurs at around 4 mm/day, transporting all other proteins (eg myosin, clathrin).

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====Retrograde Transport====

====Retrograde Transport====

Retrograde transport returns materials from the axon terminal to the cell body, either for degradation or restoration and reuse. As with fast anterograde transport, particles move along microtubules. The motor molecule for retrograde transport is '''dynein''' which is a microtubule-associated ATPase. The retrograde transport system is important not only for returning material to the cell body, but also provides the means whereby target-derived trophic factors, such as nerve growth factor (NGF) for dorsal root ganglion neurons, are conveyed to the cell body where they promote cell survival.

Retrograde transport returns materials from the axon terminal to the cell body, either for degradation or restoration and reuse. As with fast anterograde transport, particles move along microtubules. The motor molecule for retrograde transport is '''dynein''' which is a microtubule-associated ATPase. The retrograde transport system is important not only for returning material to the cell body, but also provides the means whereby target-derived trophic factors, such as nerve growth factor (NGF) for dorsal root ganglion neurons, are conveyed to the cell body where they promote cell survival. Research is being undertaken into the use of trophic factors to promote cell survival during degenerative pathology. The retrograde transport system can be "hijacked" by harmful substances to gain entry to the peripheral neuron and ultimately the CNS. [[Herpesviridae|Herpes simplex virus]], [[Rhabdoviridae|rabies]], [[Tremors and Movement Disorders (Nervous System) - Pathology#Tetanus|tetanus]] and heavy metals all affect the retrograde transport system.

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===<u>The Schwann Cell</u>===

===<u>The Schwann Cell</u>===