More Motor Pathways Flashcards
axonal degeneration occurring distal to the site of injury
orthograde degeneration
what happens with orthograde degeneration
result in the Schwann cells reorganizing into Schwann tubes that can play a critical role in regeneration
If no regeneration after 1 yr, Schwann cells are replaced with fibroblasts
numbness after surgery or injury
has year with schwann tube still there to replace and if not, gets fibroblasts = scar tissue
instead of open channel road, you have a road block that hinders regeneration and that is this scar tissue
accompanies orthograde, axonal degeneration occurs proximal to the site of injury.
retrograde degeneration
what happens with retrograde degeneration
Loss of neurotrophic factors coming from the axon to the cell body via retrograde axoplasmic flow
Soma becomes swollen
loses communication with its end so cell body starts to change
Injury potentials from depolarization at the site of the lesion evoke spontaneous action potentials that travel to the muscle, causing a twitch
stage 1, fasciculations
injury potentials that lead to uncoordinated contractions of the muscle known as fibrillations
Small contractions, not visible on the surface
stage 2 of denervated muscle stages
after the distal axon has degenerated, the muscle begins to show denervation atrophy
stage 3
Denervated muscle develops a large number of ________ sites that are targets for regenerating axons
These can be maintained for about 2 years and will be lost if no reinnervation occurs
acetylcholine receptor
cell body reorganizes, they want to grow a new sprout, produces material and grows this
regeneration
describe the process of regeneration
nerve is cut and nerve degenerates, so now cell body creates more production and creates a growth cone and sends out sprouts., if it finds the schwann tube, it gets all the nutrients and regrows and reinnervates the muscle and the other sprouts dont go anywhere
the one with the right channel grows and the others do not
can regenerate nerves in the periphery
referred to as the vestibulocerebellum
flocculonodular lobe
Receives vestibular, spinal and cortical inputs
cerebellum
what is medulloblastoma
occurring in the roof of 4th ventricle in young children
Damage to flocculonodular lobe
in cerebellum
symptoms of medulloblastoma
Loss of equilibrium, sway side to side, staggering, wide-based gait, falling over, problems with eye movements, can also have noncommunicating hydrocephalus
these cells give the arbor vitae appearance
Purkinje cells
what can we see with damage to the cerebellum?
general incoordination or ataxia (“lack of order”), often in leg movements
changes in muscle tone (hypotonia), reflexes (hyporeflexia) and coordination of voluntary movements ipsi to side of lesion
how is coordination affected with cerebellar disorders?
Voluntary movements may take longer than normal to initiate
Problems stopping or changing direction of movement (overshoot or undershoot of targets = dysmetria)
overshooting or undershooting of targets
dysmetria
difficulty with rapid alternating movements
Dysdiadochokinesia
the largest and it emerges from the basal pons
mainly contains afferents from contra and pontine nuclei
middle cerebellar peduncle
has many decussations and mainly efferent pathways from cerebellum to red nucleus and thalamus
superior cerebellar peduncles
major portion of inferior cerebellar peduncle (“ropelike”) with fibers from spinal cord and brainstem
restiform body
additional fibers of the ICP (inferior cerebellar peduncle) connecting cerebellum and vestibular nuclei
juxstarestiform body
Where is there a better prognosis for regeneration?
better prognosis in peripheral ns than in the cns and for it to occur accurately
if damage is cns, so tightly packed with a bunch of cells that it has more odds against it to have an effective regeneration
