L6 - motor systems 1 Flashcards
2 neurons in the descending tracts
upper motor neuron (UMN) and lower motor neuron(LMN)
effects due to damage done to UMN
muscel weakness
- decrease muscle tone
function of cerebellum
- involved in brainstem mechanisms
-control of muscle tone
-sensorimotor coordination
motor learning
function of basal ganglia q
integ of sensory and motor info
3 components of cerebellum
spino cereb-
vestibulo cereb
cerebro cerrebellum
function of spino cereb
function is receiving sensory input and output to the reticular tract via reticulospinal
and red nucleus via rubrospinal
-
function fo vestibulo cerreb
input from and output to vesticular nucelaus via vestibulospinal tract
- control over posture and balance and eye movement
function of cerebo cerebellum
instructs primary motor cortex about movement, direction
- compares intended movements with actual movements
inputs to the purkjine cells in the outer layer of cerebullum
- climbing fibres from inferior olive
- mossy fibres from the brainstem nuclei
what part of the cerbellum can compare input from the mossy, climbing fibres and purkinje jibres
deep cerebellar nuclei (DCN)
what is basal ganglia
group of subcortical nuclei responsible primarily for motor control from the cortex
- relays back to cortex via thalamus
- initiation of vol movement
what is motor loop
a loop linking basal
ganglia, thalamus and cortex
- the loop is activated (disinhibition) to coordinate movement
structures in the basal ganglia
striatum (STR)
globus pallidus (GP)
substantia nigra
subthalamic nucleus (STN)
two pathways in the basal ganglia
direct and indirect
what is the direcft pathway in the basal ganglia
cortex > straitum > SNr and GPi > thalamus > cortex
- the striatum is activated by dopamine on the D1 receptors
- this promotes movement
what is the indirect pathway in the basal ganglia
- cortex > straitum > GPe> STN> SNr and GP i > thalamus > cortex
the straitum is activated by the dopamine on inhibitory D2 receptors
- faciliates movement
what happens when there is an imbalance between the direct and indirect pathways
- motor dysfunction
like hypo and hyperkinetic diseases
eg of hypokinetic diease
parkinson disease PD
symptoms of PD
tremor, bradykineasa( slowness of movement ), rigidity
cause of the PD in the basal ganglua
DOPamine loss int he basal ganglia -
treatments for PD
drugs like
L-DOPA - precursor for dopamine
- dompamine agonists,
-drugs that reduce dopamine breakdown
eg of hyperkinetic disease
huntingdon’s disease (HD)
symptoms of HD
excessive movment
uncontrollable rapid motor patterns
effect of HD in the basal ganglia
loss of straital output neurons in the indrect pathway
- leads to involuntary movement
results of damage done to spino cerebellum
hypotonia - reduced muscle tone
dysmetria - inaccurate termination of movement
result of damage to vestibulocerebellum
slow saccades - ocular movement impaired
Ataxia - unsteady gait
result of damage of cerebro cerebellum
ataxia
dystemetria
uncoordinated agonist and antagonist muscles
inarticulate speech
what does DCN do iif there is a difference between the intended and actual movements
send a compensatory response to the brainstem and thalamus
relationship between BG and thalamus when in a normal state
the BG inhibits thalamus so no movement is initaited
cons of using L-DOPA as a drug for PD
effectiveness reduce over time
- need to increase dose freq over time
alternatives of using LDOPA
DOPAMINE receptor agonist
what happends during surgey for PD
STN in the BG inactivated
treatment for HD
tetrabenazine - reduces DA storage and release
Chlorpromazine - DA antagonist
other hyperkinetic idsorders
HEMIBallismus
tardive dyskinesia
