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NS 11: Motor Pathways (i) (int capsule (lat to thal, white matter (axons),…
NS 11: Motor Pathways (i)
monosynaptic neurons
respond to stimulus without being controlled
e.g. stretch-contract reflex
controlled responses to stimuli
afferent (sensory)
3 neurons
message sent up to higher centre (SS cortex/postcentral gyrus of parietal lobe)
efferent (motor)
2 neurons
message down to effector from higher centre (motor cortex/precentral gyrus of frontal lobe)
central sulcus between SS + motor cortex
cerebral peduncles
attach midbrain to this (hence cerebrum)
medulla
pyramids in mildine
olives lat
lat ventricle below corpus callous
int capsule
lat to thal
white matter (axons)
genu = flexure form from corticobulbar tracts
post. limb form from corticospinal tracts
lentiform nucleus
a.k.a putamen + globus pallidus
grey matter (cell bodies)
lat to int capsule
heads of caudate nucelus
lat to lat ventricle
ant to thal
grey matter
pyramidal system
starts in motor cortex -> genu/pst. limb -> midbrain via peduncles -> pons -> medulla (85% decussate lat to corticospinal tracts)
pass though pyramids
control conscious movement
2 neurons
UMN
divided based on cranial + spinal Ns...
2) cortiocospinal tracts
UMN starts in cortex, decussates in pyramids + synapses in cord
1) corticobulbar tracts
UMN starts in cortex + synapses in brainstem
LMN (from brainstem/cord to effector muscle)
extrapyramidal system
doesn't start in motor cortex
instead in basal ganglia
lentiform nucleus
caudate nucleus
substantia nigra
fine tune movement
don't pass through pyramids
thal
sensory relay station
2nd + 3rd order neurons synapse
motor homunculus
body is inverted on motor + SS cortices
head + arms inferolat on motor cortex
supplied by middle cerebral art
80% of strokes
feet in areas of motor cortex supplied by ant cerebral art (usually unaffected in strokes)
paralysis
hemiplegia: one 1 side of body
monoplegia: in one limb/region
spinal cord
right = sensory
left = motor