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NROC64: Lec 8: Brain Control of Movement (nearly word-for-word what was said in lecture).docx

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University of Toronto Scarborough

NROC64 Lec 8 Brain Control of MovementSAQ What is the inverse modelANSWER Cortical structures that convert a sensory intention or goal into a motor command You need info about what you need to do in order to achieve that sensory goal Example of sensory goal would be to have fovea look at next word while youre reading In our motor system we have knowledge about how to achieve that sensory goal for the most part Inverse modelconvert sensory goal into potential motor action that can be executed in order to achieve sensory goalSlide 4 Introductionbrain influences activity of spinal cord o voluntary movements although sometimes unconscious and not controlled by volition hierarchy of motor control o highest levelstrategy o middle leveltactics planning the execution o lowest levelexecutionalso involves sensory system sensorimotor system o proprioception is critical for motor controlSlide 7 Descending spinal tractsspinal cord at the bottom and there are several pathways that project onto spinal cord o lateral pathwaysred nucleus rubrospinal tractcorticospinal tract o ventromedial pathwaysreticular nuclei superior colliculus and vestibular nucleidistinction from lateral and ventromedial come from when you transect thru spinal cord these sections are clearly separated and function separatelySlide 8 Lateral pathwaysspecifically involved in voluntary movement of distal muscles esp flexorscomponents o corticospinal tractpyramidal tractstarting pointcortico end pointspinal ventral horndecussation in spinal cord o rubrospinal tractstarting pointred nucleus in midbraindecussation happens here end pointspinal ventral horncorticospinal tract is the more dominant lateral pathway in humans whereas rubrospinal tract has lost most of its significancelesions in lateral pathway may still allow individual to move effectors independently like your hand but to move your fingers will be difficult3Slide 12 Ventromedial pathwaysposture and locomotionmostly project to alpha motor neurons that innervate proximal and axial muscles whereas lateral pathway is to distal musclesunder brainstem controlVestibulospinal tracts o Projects from vestibular nuclei in medulla o Innervates neck muscles in order to stabilize vision when youre walking without thinking you correct your head posture so that your eyes arent shaking all the time o Also involved in posture to the legs stretch reflex to prevent you from fallingTectospinal tract o Projects from superior colliculus tectum o Involved in orienting and attention o Highly salient stimulus turn your head towards it often a combo of eye and head movementshead for gaze movementsPontine and Medullary reticulospinal tract o Antigravity reflexesSlide 14 LesionsLesion of spinal cord affecting the alpha motor neurons o Lack of innervation of muscles themselvesparesis paralysis o Atrophy of muscles if no innervationLesion above the spinal cord central lesions produce opposite effects o At the beginning when you get injury may go thru spinal shock phase hypotonia hemiplegiawhich is kind of similar to lesion of motor neurons of spinal cord o Hypertonia muscles continuously contracted hyperreflexia Babinski naturally in babies stretches out o Babinski in braindamaged like in MS lack of influence of brain onto alpha motor neurons then you get increase in certain reflexesPLANNING OF MOVEMENT BY CEREBRAL CORTEXSlide 16 Cerebral cortexMotor CortexArea 4 M1posterior portion of precentral gyrus next to central sulcus and area 6 of frontal lobeArea 6premotor area parts going into the fold are supplementary motor areasArea S1area 3 and areas 1 and 2 behind that are also involved in motor control with direct projectionsArea 5 which mainly gets inputs from somatosensory cortex o Important in motor controlArea 7 which gets inputs from visual areas o Important in motor control eye movement controlSeveral areas involved in motor control but then the entire brain is involved
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