lecture 15 and 16

lecture 15 and 16 - Control of movement From muscles to...

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Control of movement From muscles to cortex
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Movement Movement is the planning, coordination & execution of a motor program that relies on information provided by the sensory system. Movement is controlled by the motor systems of the brain and spinal cord. Motor systems translate neural signals into contractile force in muscles. Allows us to maintain balance and posture, move our body, limbs, eyes, tongue & communicate through speech and gesture. Eadweard Muybridge’s Animal Locomotion series
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Types of movement ReFex responses - knee jerk, withdrawal from pain, swallowing. Muscle contractions and relaxations that are rapid, stereotyped, involuntary and coordinated. Rhythmic motor patterns - walking, running, chewing. Typically initiation and termination are voluntary and triggered by peripheral stimuli. Voluntary movements - initiated movements to accomplish a speci±c goal (e.g. piano playing, writing). These are goal directed and largely learned movements that improve with practice, as one learns to anticipate and correct for environmental obstacles.
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Organization of Neural Structures Involved in Movement Control Lower motor system State of muscle contraction/relaxation Upper motor system Execute movement Output system Motor learning Gating
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Muscles Relaxation and contraction. Muscles can pull but not push. Thus separate sets of muscles at the opposite sides of joints must mediate Fexion or extension. Movements at a joint engage two opposing sets of muscles.
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Muscle contraction smooth muscle using mACh receptors
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1) Action Potential in Motor Axon 2) End Plate Potential at Neuromuscular Junction 3) Action Potential in Muscle Fiber. 4) The AP in the muscle fber is ±ollowed by a twitch in the muscle fber Twitch = transient all-or-none contraction Coupling o± Excitation & Contraction
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The physiology of muscle contraction
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Summation of muscle force as a function of stimulation rate Fig. 16.7
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The Motor Unit A motor unit is the sum total of extrafusal skeletal muscle fibers within a muscle that are innervated by a single α motor neuron. An action potential normally brings to threshold all muscle fibers it contacts.
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α -motor axon Motor endplates
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Types of motor unit Slow (S) motor unit. Small motor neurons innervate relatively few muscle Fbers and generate small forces. They innervate small “red” muscle Fbers that contract
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lecture 15 and 16 - Control of movement From muscles to...

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