Anatomy and Cell Biology 3319 Lecture Notes - Lecture 11: Superior Colliculus, Plantar Reflex, Stretch Reflex
2 Aug 2019
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MOTOR PATHWAYS
DESCENDING PATHWAYS
°decussate at some point Vendotrgaaonnlymentorymhg
°always multi neuron
somatotopy tracts arranged according to body region they supply
intra pyramidal systems cortical spinal tracts ,cortical but beer tracts ;voluntary concious movement
extrapyramidal systems cause involuntary movements bc don't pass through pyramids of medulla
upper motor neurons originate in gray matter of brain tsend long axons down descending tracts ;synapse wlower motor neurons
lower motor neurons ventral horn ;axons exit via ventral roots tinnervate muscles tglands of body
°5major descending pathways :§corticospinal pathway
2corti co bulbar pathway
③reticule spinal pathway
④vestibule spinal pathway
⑤rub wspinal pathway
ELEMENTS OF DESCENDING PATHWAYS
motor unit group of extra fus at muscle fibers tamotor neuron innervates them
upper motor neuron lesion causes spastic paralysis ,exaggerated stretch reflexes ,abnormal Babinski reflex ,Usu .w/o atrophy
lower motor neuron lesion causes flaccid paralysis ,loss of stretch reflex ,
tatrophy
CORTICOSPINAL (PYRAMIDAL )TRACT
ocontrols precision +speed of skilled movements
°direct pathways that extend from pyramidal cells in cerebral cortex →spinal cord w/o synapsing
°axons of pyramidal cells (upper motor neurons )descend from motor cortex via internal capsule
°extend from primary motor tpremotor cortex ,travel through cerebral peduncle
°fibers of lateral corticospinal tract decussate @medulla
°fibers of ventral corticospinal tract decussate in spinal cord
°synapse on lower motor neurons directly Iindirectly
°control limb muscles ,esp .hands +fingers ,for precise ,skilled movements
oventral tlateral corticospinal tract terminate same but diff decussation
↳ventral ipsilateral ,later decussate s@medulla
↳ensures contralateral control in brain
*left motor cortex controls right skeletal muscles tvice versa R
TEC TO SPINAL PATHWAY
ospecific function of turning neck so eyes can track moving objects
°originates from superior colliculus of midbrain
°decussate to contralateral side
°terminates in ventral horn
