2217 Motor system Somatic striated muscle Autonomic smooth

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2217 – Motor system Somatic – striated muscle Autonomic – smooth muscle, cardiac muscle,

2217 – Motor system Somatic – striated muscle Autonomic – smooth muscle, cardiac muscle, glands Upper and lower motor neurons (final common path) Segmental (reflexes) and suprasegmental control Pyramidal vs ‘extrapyramidal’ systems

Reflexes

Reflexes

Descending Pathways • Pyramidal system • Extrapyramidal system – basal ganglia, thalamus – red

Descending Pathways • Pyramidal system • Extrapyramidal system – basal ganglia, thalamus – red nucleus – subthalamic nuclei – substantia nigra – reticular formation – vestibulo-spinal? – tecto-spinal? – cerebellum?

Pyramidal Tracts Pyramidal cells in the primary motor cortex A major tract in primates

Pyramidal Tracts Pyramidal cells in the primary motor cortex A major tract in primates Mainly for fine motor control Homunculus in primary motor cortex

From cortex (only about 50% from primary motor cortex) Passes through the posterior limb

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 corticobulbar 50 -55% end in cervical cord 5 -10% direct on motor neurons Damage effects not as bad as might be expected from its size corticospinal

Extrapyramidal pathways Tectospinal Rubrospinal Reticulospinal Vestibulospinal

Extrapyramidal pathways Tectospinal Rubrospinal Reticulospinal Vestibulospinal

Extra-pyramidal tracts • Tegmento-spinal(7) • Rubro-spinal(8) • Medial long. Fasc. (10) • Tecto-spinal(9) •

Extra-pyramidal tracts • Tegmento-spinal(7) • Rubro-spinal(8) • Medial long. Fasc. (10) • Tecto-spinal(9) • Reticulo-spinal(6, 5) • Vestibulo-spinal(4)

The basal ganglia

The basal ganglia

Basal Ganglia

Basal Ganglia

“Striatum” Caudate Putamen Globus pallidus Basal ganglia = caudate nucleus and lenticular (lentiform) nucleus

“Striatum” Caudate Putamen Globus pallidus Basal ganglia = caudate nucleus and lenticular (lentiform) nucleus Lenticular nucleus = Globus pallidus + putamen

Kandel et al

Kandel et al

Basal ganglia problems • • Involuntary movement at rest Hypokinesia A “mask” like face

Basal ganglia problems • • Involuntary movement at rest Hypokinesia A “mask” like face Rigidity • • Typical of Parkinson’s disease Treated by L-Dopa Experimentally by fetal grafts (stem cell grafts ? ? ) Globus pallidus, subthalmic nucleus lesions

Cerebellum

Cerebellum

CEREBELLUM

CEREBELLUM

Cerebellar Movement Disorders • Dysmetria - over-reaching (test by touching your nose) DISTANCE •

Cerebellar Movement Disorders • Dysmetria - over-reaching (test by touching your nose) DISTANCE • Disdiadochokinesia - disjointed movement, poor timing (touch fingers in order) TIMING • Dyssynergia - disjointed force (touch examiner’s finger) FORCE • Ataxia - poor coordination (all the above) • Clonus - contraction in response to stretch • Paresis - weakness, partial paralysis

Movement deficits associated with large cerebellar lesions Disruption of spatial accuracy and temporal coordination

Movement deficits associated with large cerebellar lesions Disruption of spatial accuracy and temporal coordination of movements