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2217 Motor systemSomatic striated muscleAutonomic smooth muscle, cardiac muscle, glands
Upper and lower motor neurons (final common path)Segmental (reflexes) and suprasegmental controlPyramidal vs extrapyramidal systems
Reflexes
Descending PathwaysPyramidal systemExtrapyramidal systembasal ganglia, thalamusred nucleussubthalamic nucleisubstantia nigrareticular formationvestibulo-spinal?tecto-spinal?cerebellum?
Pyramidal TractsPyramidal cells in the primary motorcortexA major tract in primatesMainly for fine motor controlHomunculus in primary motor cortex
From cortex (only about 50% from primary motor cortex)
Passes through the posterior limb of the internal capsule in somatotopic order
Passes through cerebral peduncles
Sends branches off to bulbar nuclei (both ipsi and contra)
At pyramids 85% cross midline
50-55% end in cervical cord
5-10% direct on motor neurons
Damage effects not as bad as might be expected from its size
cortico-bulbarcortico-spinal
Extrapyramidal pathwaysTectospinalRubrospinalReticulospinalVestibulospinal
Extra-pyramidal tractsTegmento-spinal(7) Rubro-spinal(8)Medial long. Fasc.(10)Tecto-spinal(9)Reticulo-spinal(6,5)Vestibulo-spinal(4)
The basal ganglia
Basal Ganglia
StriatumCaudatePutamenGlobus pallidusBasal ganglia = caudate nucleus and lenticular (lentiform) nucleus
Lenticular nucleus = Globus pallidus + putamen
Kandel et al
Basal ganglia problemsInvoluntary movement at restHypokinesiaA mask like faceRigidity
Typical of Parkinsons diseaseTreated by L-DopaExperimentally by fetal grafts (stem cell grafts ??) Globus pallidus, subthalmic nucleus lesions
Cerebellum
CEREBELLUM
Cerebellar Movement DisordersDysmetria - over-reaching (test by touching your nose) DISTANCEDisdiadochokinesia - disjointed movement, poor timing (touch fingers in order) TIMINGDyssynergia - disjointed force (touch examiners finger) FORCEAtaxia - poor coordination (all the above)Clonus - contraction in response to stretchParesis - weakness, partial paralysis
Movement deficits associated with large cerebellar lesionsDisruption of spatial accuracy and temporal coordination of movements