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KIN 461 Week 4

by: Tanski Notetaker

KIN 461 Week 4 KIN 461-401

Tanski Notetaker
GPA 3.7

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Hi everyone! Here are the notes for Week 4 of Motor Learning. Hope they help!
Principles of Motor Learning
Dr. Peterson
Class Notes
Kinesiology 461 More Learning KIN kin Kins KINS week 4
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This 5 page Class Notes was uploaded by Tanski Notetaker on Saturday February 20, 2016. The Class Notes belongs to KIN 461-401 at University of Wisconsin - Milwaukee taught by Dr. Peterson in Spring 2016. Since its upload, it has received 17 views. For similar materials see Principles of Motor Learning in Kinesiology at University of Wisconsin - Milwaukee.


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Date Created: 02/20/16
Week 4 Tanski 1 Motor Units and EMG (cont.) Some terminology  Recruitment threshold: force at which a motor unit becomes active  Orderly recruitment: recruiting motor units according to size o Advantage: simplifies the task o Disadvantages: can’t immediately generate great amount of force  Derecruitment: motor unit that is active stops being active   Rate coding: modulating firing rate (or discharge rate)  Interspike interval: time between two spikes o The larger it is, the lower the discharge rate  Double discharges: motor neuron firing twice in 10 milliseconds o Ramp up force quickly  Motor unit synchronization: idea that there is shared activity across motor units o Piano players have low motor unit synchronization because need small, precise  movements o Olympic weight lifters have high motor unit synchronization  Common drive: waves of period excitation in motor unit pool o Increase in common drive can cause tremors EMG  One of the few techniques available to examine the neuromuscular system in humans  performing voluntary contractions  Also able to monitor the response of the neuromuscular system to electrical stimulation  The image below is of electrical stimulation.  You can calculate EMG amplitude by drawing an outline around the rectified EMG o Called a filtered EMG o Image below Week 4 Tanski 2  EMG issues o Varies from muscle to muscle o Extracellular, not intracellular recordings o Influenced by many different factors o Amplitude cancellation: when positive and negative signals cancel each other  out o Location on muscle (e.g. innervation zone) o Filtering (e.g. movement noise, 60 hz. Noise) o Cross talk  EMG during electrically­evoked contractions o Test the integrity of the motor system o EMG is more reliable measure of muscle activity during isometric contraction Spinal Reflexes  Every movement requires coordinated action of many muscles  Motor coordination: process of linking the contractions of independent muscles so that  they act together  Reflex is the most elementary form of motor coordination o Relatively stereotyped response to a specific sensory stimulus o 2 important features of a stimulus  Locus of the stimulus  Determines which muscls will contract to produce reflex response  Strength   Determines amplitude of response o Increased strength = greater amplitude  Reflexes are graded in intensity Week 4 Tanski 3  Neural circuitry responsible for a reflex is located within spinal cord  Spinal reflexes have essential role in all voluntary movement  Importance clinically o Absent or weak reflex:  Muscle spindle, Ia afferent axon, motor neuron, motor efferent axon, or  muscle  o Hyperactive (e.g., spasticity, rigidity)  Central lesions   Most spinal reflexes are polysynaptic­ one or more interneurons are interposed between  sensory and motor neurons Stretch Reflex  Stretch reflex is monosynaptic­ it’s produced by a two­neuron circuit consisting of a  single set of synaptic connections o KNOW HOW TO DRAW MONOSYNAPTIC STRETCH REFLEX  Reciprocal innervation: causes excitation of the motor neurons to the stretch muscles  (synergist muscles) and inhibition of motor neurons to the antagonist muscles o Role of Ia inhibitory interneurons  Synergist muscles control the same joint and have a similar mechanic action  Negative feedback: circuitry of stretch reflex acts as a loop to resist changes in muscle  length  Stretch reflexes regulate muscle tone o Muscle tone: the fore with which a muscle resists being lengthened   Serves important functions  Assists in maintaining posture  Allows muscles to store energy, like springs, and release it later  Spring­like qualities of muscles help to smooth movements Spinal Reflexes in General Week 4 Tanski 4  Spinal reflexes are governed by 3 main levels of control o Control of individual muscles o Coordination of muscle action around a single joint o Coordination of muscle at several joints  Muscle action around a joint is coordination by inhibitory interneurons o Prevents muscles from acting independently of each other o Group Ia inhibitory interneurons inhibit antagonist muscles.  Mediate reciprocal inhibition through excitatory inputs from the muscle  spindle afferents  This way high motor centers do not need to send separate commands to  opposing muscles  Limits co­contraction, which is contraction of both prime mover and  antagonist muscles simultaneously o Group Ib inhibitory interneuron inhibits homonymous motor neurons  Receives input from Golgi tendon organs  Provides negative feedback mechanism for regulating muscle tension   Signaled by an increase in in Golgi tendon organs  Inhibits the homonymous motor neurons = decreases muscle tension  Protective mechanism  Crossed extension reflex: flexion of stimulated limb produced opposite effect in  contralateral limb o Enhances postural support o What happens when you step on something sharp  Nociceptor: pain receptor  Excite flexors while inhibiting extensor in leg you are trying to pick up  Crossed extension reflex excites the extensors in the opposite leg to  maintain posture  Certain reflexes consist of rhythmic movements o Ex: scratch reflex which is not seen in humans  Main features of walking movements are controlled by the spinal cord o Central Pattern Generators (CPGS)  Local spinal circuits that coordinate the contraction of the several muscle  groups needed to generate rhythmic stepping  Simplifies the control of locomotion Voluntary Movement  Voluntary Movement o Primary motor cortex o Premotor cortical areas o Cerebellum o Basal Ganglia  Neurons in the primary motor cortex encode force an direction  Movement direction is encoded by population of cortical neurons Week 4 Tanski 5  Neurons in premotor cortical areas prepare the motor system for movement o Activity of neurons in supplemental motor area is linked to planning of  movements  Neurons in the cerebellum regulate movement indirectly and participate in motor learning o Coordination and motor adaptation  Premotor cortical areas prepare   Basal ganglia processes information needed for triggering self­initiated movement


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