PED 1323 Motor Control & Motor Learning

Passive muscle length change demonstration top emg of

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PASSIVE MUSCLE LENGTH CHANGE DEMONSTRATION top: EMG of finger extensor muscle (MUSCLE IS QUIET = PASSIVE MOVEMENT) next line: finger position. Line down = finger up = short muscle Line up = finger down = stretched muscle bottom 2 lines: firing rate of spindle Ia afferent observe: with passive movement of the subject’s finger by an experimenter Line down, finger up, short muscle = low Ia firing rate as line moves up, finger moves down, muscle lengthens = increase Ia firing rate Line down again, finger up, short muscle = low Ia firing rate What would happen to spindle firing rate with a FASTER stretch? Biceps Ia firing rate and muscle length - slow stretch 0 10 20 30 40 50 0 0.18 0.36 0.54 0.71 0.89 1.07 1.25 Time (seconds 0 100 200 300 400 500 600 700 800 900 MUSCLE LENGTH Ia FIRING RATE Muscle held at short length Muscle held at long length Slow m uscle stretch to longer length
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Motor Control Section 1: The Stretch Shortening Cycle (a.k.a. plyometric movements) Unit 2: Sensory Receptors Biceps Ia firing rate and muscle length - fas stretch 0 10 20 30 40 50 0 0.18 0.36 0.54 0.71 0.89 1.07 1.25 Time (seconds 0 100 200 300 400 500 600 700 800 900 MUSCLE LENGTH Ia FIRING RATE Muscle held at short length Muscle held at long length Fast m uscle stretch to longer length Postgrad/PaulM/Kinaesth.htm Sensory   events from  external  environment BRAIN & BRAIN STEM SPINAL CORD VENTRAL  ROOT DORSAL  ROOT M u s c l e Displacement Sensory  consequences  of movement Afferent  input
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Motor Control Section 1: The Stretch Shortening Cycle (a.k.a. plyometric movements) Unit 3: Stretch Reflexes The Stretch Reflex Holding a cup full of water in your upward turned palm (elbow @ 90 degrees) a crow lands on your palm to drink from the cup Q1: What happens to your hand & elbow position? Q2: What happens to the output from the biceps spindle? WHAT IS THE EFFECT OF THIS SPINDLE OUTPUT? Ia afferent synapses (excitatory synapse) onto all of the α motor neurons innervating the HOMONYMOUS (same) muscle Complete the following illustration to indicate what happens during the stretch reflex Load muscle  length Ia afferent  discharge alpha  MN  discharge desired shorter longer low high crow  lands biceps  EMG What accounts for difference in reflex speed between people? Does training have an effect on motoneuron morphology? REFLEX EXAMPLE: While walking toward the PEHR hall door, you prepare to push on the door and keep walking. But the door is much heavier than you expect, and does
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Motor Control Section 1: The Stretch Shortening Cycle (a.k.a. plyometric movements) Unit 3: Stretch Reflexes not move, but you can’t slow your body down. Explain how reflexes help you. (use a flow chart) Combined drive from brain & stretch reflex determines activation of the motoneuron and the muscle See: Zuur AT, Lundbye-Jensen J, Leukel C, Taube W, Grey MJ, Gollhofer A, Nielsen JB, Gruber M.
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  • Fall '11
  • John Smith
  • The Land, Motor control, Gordon Chalmers

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