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neuron degeneration

WVSOM -- Medical Neuroanatomy -- Neuron Degeneration and Regeneration

Why is axonal transport necessary? no protein synthesis takes place in the axon so all proteins assembled in the soma needs to be transported to where needed
What is anterograde transport? movement of materials away from the cell body
What is retrograde transport? movement of materials toward the cell body
How are proteins transported thru the axon? on an intracellular railroad composed of microtubles. uses energy generated by oxidative phosphorylation.
Is axonal transport and electrical activity dependant on each other? no they are independant of each other
Explain how microtubules are arranged have a + and - end to the microtubule. They orient themselves where the + meets the - end and the + end is going away from the soma
Explain rapid anterograde transport moves at a rate of ~400 mm/day. Carries membrane proteins, vesicles and lipids. used for neuron maintenance
Explain slow anterograde transport Carries soluble enzymes and structural proteins such as the microtubule protein, tubulin. Slow transport rate and it is what determines the rate of recovery fllowing neuron injury. ~1mm/day
What is kinesin an ATPase protein-complex needed for anterograde transport. Connects to both microtuble and the molecule to be transported. with ATP kinesin undergoes a conformational change that walks the molecule to the + end of the tubule
explain retrograde transport brings substances from the axon to the soma. Regulates metabolism in the cell. Some viruses and neurotoxins enter peripheral nerve endings and move to infect the neuronal soma via retrograde transport
What is dynein? ATPase that works similarly to kinesin except it moves in the opposite direction. used in retrograde transport.
Explain axon degeneration axonal segments distal to lesion degenerate. myelin sheaths srruound the distal parts and being ot break down. Occurs in direction of nerve impulse conduction.
Can CNS neurons regenerate after injury? no
What happens to an area where CNS neurons die? a glial scar forms
How do PNS regenerate? schwann cells remove the degenerated debris by phagocytosis over a period of months. Empty endoneural tubes lined with schwann cells remain. proximal axon stump begins to send out axonal sprouts in a growth cone. search for endoneural tubes
What is likelihood of long distance PNS regeneration? unlikely as they regenerate into wrong regions most times.
What happens if scar tissue is in the way of regenerating nerves? blocks regeneration and a plexiform neuroma occurs
What are the characteristics of regenerated axons? thin and unmyelinated
How do growth cones know where to go? endoneural tubes as well as the fact that post-synaptic targets of neurons secrete a growth factor to help direct them
What happens to damaged neurons in CNS? microglial cells phagocytose adn degernate debris and astrocytes from a glial scar tissue. no endoneurial tubes are formed.
Created by: tjamrose