Lecture 8 : Nerve and Muscle : Degradation and Re-innervation Flashcards
Good summary of pathways of nervous system
What is the descending pathway
The descending pathway in the nervous system refers to nerve tracts that carry motor signals from the brain to the spinal cord to control voluntary and involuntary movements. Mainly influence muscle activity.
Corticospinal Tract – Controls voluntary movements, especially fine motor control.
Corticobulbar Tract – Controls muscles of the face and head via cranial nerves.
Vestibulospinal Tract – Maintains posture and balance.
Reticulospinal Tract – Regulates muscle tone and reflexes.
Rubrospinal Tract – Assists in motor control, particularly limb movements.
What causes degeneration of nerves?
- Genetics
- Natural aging processes
- Injury (lacerations)
Can CNS neurones regenerate? What about peripheral nerves?
- CNS neurones do not regenerate
- Peripheral nerves can regenerate but responses of injury depend on location within the neuraxis
What structure of neurone are likely to be affected by insult
What is Seddon’s classification of nerve injury
Neuropraxia, axonotomesis and neurotmesis visualisation
What is neuropraxis
- Neurone temporarily loses its ability to function normally
- Injury most likely affects myelin sheath only
- Eg. Temporary compression of nerve fibre so blood supply is lost
- Restoration of function would be COMPLETE upon recovery
What is axonotomesis?
Restoration :
- Motor and sensory nerves are affected in same way
- If endoneurium, perineurium and epineurium are in tact, new nerve sprouts re-supply target effector / affector to restore normal function of injured nerve
- Complete restoration of function after a full recovery
What is neurotmesis?
- When the entire nerve fibre is completely transected or severed
- Most severe class of nerve damage by Seddon’s classification system
- Axon and connective tissue of nerve cell are damaged
- Recovery of function is NOT expected
