NS 5: Motor disorders and patterns of sensory deficits Flashcards
In which region of the brain does degeneration of dopaminergic neurones take place in Parkinson’s disease?
the substantia nigra pars compacta= pars compacta is a portion of the substantia nigra which is located in the midbrain (mesencephalon)
damage to what causes an UMNLs?
motor tracts of brain and SC
damage to what causes LMNLs?
crainal or spinal motor nuclei, or peripheral nerves
extrapyramidal signs are related to dysfunction of what structures?
non-cortical motor systems e.g. basal ganglia and cerebellum.
and extrapyramidal tracts.
Damage to extrapyramidal tracts (originate from brainstem motor nuclei) impairs way movements carried out e.g. gait abnormality.
how does damage to corticospinal tract (pyramidal tract) impair fine movements?
it impairs the ability to decide on and commit to performing fine movements
describe the features of spinal shock
this occurs following severe damage to descending tracts of SC. May last for wks or mnths, and charactersised by flaccid paralysis and areflexia.
Limbs eventually become spastic and show hyperactive deep reflexes typical of UMN damage.
Loss of reflex activity due to loss of motor influences exerted by descending fibres from reticular formation, allowing intact connections in reflex circuits to become dominant, producing UMN signs.
* inital loss of reflexes result of loss of basal excitatory stimulation to nuerones which become hyperpolarised and so less responsive to stimuli.
in which 4 places might a lesion lie to result in lower motor neurone signs?
cell bodies of alpha motorneurones
axons of alpha motorneurones
NMJ
muscle itself
what does muscle tone depend solely on the operation of?
the muscle stretch reflex
why are UMNLs characterised by hypertonia?
reduced descending inhibition from extrapyramidal system to muscle stretch reflexes
why is overall flexion of upper limb often seen with UMNLs?
flexors of UL usually stronger than extensors so spastic paralysis with hypertonia usually causes overall flexion.
3 functional zones of cerebellar cortex?
vestibulocerebellum
spinocerebellum
cerebrocerebellum
function of vestibulocerebellum?
balance and ocular reflexes
main input from vestibular system (vestibular nucleus in pons and medulla- vestibulospinal tract- extrapyramidal pathway from brainstem to SC)
function of spinocerebellum?
involved in error correction
function of cerebrocerebellum?
involved in movement planning and motor learning, part. in relation to visually guided movements and coordination of muscle activation
sings of cerebellar dysfunction?
ataxia past pointing (dysmetria) 'scanning' speech (dysarthria- pronunciation difficult) dysequilibrium hypotonia dysdiadochokinesia cannot learn new movements coarse nystagmus no muscle weakness/atrophy