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Lecture 4

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Life Sciences
Ramesh Balasubramaniam

ecture 4 September-13-12 3:32 PM  Voluntary movement o Whether big or small o Require axn of agonist and antagonist muscle o Typically happens through descending neuron o Tells motoneuron to either act or not act o Usually managed by Ach system Motor commands  o Originates in motor cortex, spinal cord, to muscle o Signal from motor cortex to periphery o Desccending fibres go from cortex, through brain stem, through spinal cord, before motor neurons  The Midbrain o Control sensory and motor functions o Pursuit tracking o Automatic processes that are not reflexes (e.g. Learning to ride a bike) o Midbrain controls vestibuloocular reflex (VOR)  When you shake yourhead o Why doesn't the world get jittery? o When you take any moving plane, what ever is being reflected is also moving o When you move you head, your eyes are fixed so the world is relatively stable o The VOR is responsible for holding your eyes straight  Cerebellum o Most important organ of movement o Locus of time, motor learning, posture o Voluntary movement is largely cortical, most learned physical activity is cerebellar o The cerebellum builds models of the world (Dyslexia and autism)  Cerebellar Cortex o Hands a lot of info - 200 million inputs o Purkinje cells - input output operators of the cerebellum o Motor cortex connects to body largeley contralaterally o Cerebellum has two hemispheres as well but left side connects to left side and right side of cerebellum connects to right side of body (ipsilateral)  MS vs ALS o MS  Entire periphery is not affected  Myelination of axons is affected  Large descending fibres from motor cortex to periphery Myelination is attacked by immune system   Case study - video  Profound amt of weakness that has set in  Axonal transmission is lost  Brain is sending a signal to the periphery but it is getting lost along the way  Autoimmune disorder  Some days are ok and some days suck o ALS  Degenerative neuroomsuclar disorder  Target muscle connected to motorneurons are beginning to degrade  No good days and bad days, they just ge
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