BIOL 1013 Lecture Notes - Narcolepsy, Premotor Cortex, Midbrain Tectum
1 Feb 2013
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Motor system ii descending tracts: motor control is a high level action, e. g. it may involve complex joint motions but smooth trajectories, corticospinal tract. Origin at premotor cortex, motor cortex (m1), somatosensory cortex (s1) Axons run through pyramids (medulla) and 90% cross in lower medulla to form lateral corticospinal tract and 10% remain ipsolateral mostly going to ventral corticospinal tract. Split-brain patients (surgical separation of corpus callosum) Distribution of cst fibers provides good control of contralateral arm/hand, but poor control of. Language center is on left hemisphere, can only vocally identify items perceived by right side of ipsolateral and little control of ipso. hand body (thus left arm is an alien arm ) Conduction speed in cst increases early in life due to myelination but remains relatively constant afterwards despite growth/lengthening of pathway. Origin at tectum (midbrain), crosses in caudal midbrain, terminates in cervical spine. Function unclear (don"t worry about this tract)
