KIN 100 1st Edition Lecture 22Neural control of movement● Nerves control muscle○ muscles are combination of slow and fast twitch fibers■ not true in most vertebrate species○ Cat■ FHL Muscle● fast muscle- all muscle fibers are fast-twitch● connected to fast nerve■ SOL● slow muscle- all muscle fibers are slow-twitch● connected to slow nerve■ cut slow and fast nerve○ often regrow in peripheral nervous system● connected slow nerve to fast muscle and vice versa● slow muscle connect to fast nerve became fast muscle● fast muscle connected to slow nerve became slow muscle● Spinal cord cross-section○ CNS= brain and spinal cord○ spinal cord■ back of spinal cord-> receptors, sensory■ front-> to motor units, motor■ interneurons● only in nervous system■ gate theory of pain■ decision making○ Spinal processing■ the flexor reflex● touching hot iron○ want to respond faster than reaction time○These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.● spinal cord makes decision to contract○ want to minimize extension contraction○ stretch reflex○○ in case of need of sudden extension■ running and step in ditch■ muscles need to extend more■ excitatory signal sent to extensors and inhibitory sent to flexors● reaction time○ action potentials carry:■ stimulus receipt at receptor■ sensory cortex■ motor cortex■ motoneurons■ motor units● EMG○ Light stimulusskinreceptorflexorsexcitationextensorsinhibitionmotorneuronsinterneuronsmuscle spindleexcitationinhibitionagonistantagonist■ visual evoked potential in visual cortex■ motor evoked potential in motor cortex■ agonist EMG -> muscle fiber AP■ electromechanical delay■ movement begins○ how much time each step takes● Solving simultaneous voluntary and reflex problems○ hard when have to do both■ hockey player● thinking about shooting the puck, not staying upright on ice○ study■ asked to raise arm as fast as could● might impact balance, action reaction● would they fall backward? if not, how?■ recorded muscle activity in deltoid and inbiceps femoris (hamstring)● hypothesized message must be sent from arm to leg to stop them from falling over■ found that signal to stay balanced in leg muscles arrived before signal in arms● brain prioritizes reflex muscles overvoluntary● What controls movement speed?○ strength?○■ strength is unrelated to speed○ EMG activity■ Tricep muscle (agonist muscle)muscle strenghtspeed of movement● two bursts○ silent period-> time between bursts■ Biceps muscle (antagonist)● also activated-> protective manner○ fastest movement speed produced from latest activation of antagonist
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