Changes

===Axoplasmic Transport===

===Axoplasmic Transport===

*Neurons are very large cells and most of a neurons cytoplasm is present in its processes while most of the cells RNA is located in cell body (Nissl substance).  

Neurons are very large cells and most of a neurons cytoplasm is present in its processes while most of the cells RNA is located in cell body (Nissl substance). These cells have therefore evolved mechanisms to transport large macromolecules and organelles up and down processes.

*These cells have therefore evolved mechanisms to transport large macromolecules and organelles up and down processes.

 

====Anterograde Transport====

====Anterograde Transport====

*Two basic forms of anterograde transport can be recognised:

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).

'''''Fast anterograde transport'''''

*Transports all membranous organelles such as synaptic vesicles

*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)

**A fast component, which occurs at around 4 mm/day, transporting all other proteins (eg myosin, clathrin).

 

====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.

==WikiPath Neurolical Information==

==WikiPath Neurolical Information==