Kin121_L11_neuromuscle_physiology.ppt

Kin121_L11_neuromuscle_physiology.ppt - Kinesiology 121...

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Unformatted text preview: Kinesiology 121 Neuromuscular Physiology & Review Unless otherwise noted, all diagrams are taken /adapted from Klavora (2012) Biophysical Foundations in Kinesiology – Studying Human Movement and Health. Sport Books Publishers. Name all the primary senses: Kinesthesis Vision Hearing Smell Taste Touch Your kinesthetic sense Kinesthetic Sense Vestibular system Tells us where our body is in space Semi-circular canals in inner ear Semicircular canals From Martini Kinesthetic Sense Vestibular System Tells us where our body is in space Semi-circular canals in inner ear Proprioceptive System Tells us where our body parts are relative to our body In muscle, tendon, joint capsules Proprioception: (where our body parts are, relative to our body) 1. Muscle spindle : senses stretch in muscle Very sensitive to rate of stretch – Stretch reflex (myotatic) Stretched muscle causes reflexive contraction of muscle being stretched – Sensory impulse also sent to cerebellum From Martini From Martini Proprioception: (where our body parts are, relative to our body) 2. Tendon Receptors (Golgi tendon organ) senses muscle tension – Inverse myotatic reflex Tension on tendon causes reflexive relaxation of muscle being contracted – Sensory impulse also sent to cerebellum Proprioception: (where our body parts are, relative to our body) 3. Joint Capsule Receptors senses compression in joint capsule – Sensory impulse also sent to cerebellum motor cortex sensory cortex Sensory-Motor Integration: Vestibular input skin Joint capsule Golgi tendon organ Muscle spindle From Wilmore & Costill So where are we? • Muscles provide force - to move levers - about axes • Coordinated movement needs: sensory feedback - particularly kinesthetic feedback - specifically proprioceptive feedback So where are we? • Muscles are driven by neural impulses which can be: - volitional - reflexive • Muscle force can be neurally enhanced: - Increasing stimulation frequency - Recruiting more motor units - Synchronizing the firing of motor units - Reducing inhibitory firing Muscle force can also be enhanced by: • increasing the amount of contractile protein (hypertrophy). • The opposite is atrophy So we understand mechanical contraction: i.e. Sliding Filament Theory And we know muscle contraction needs neural drive: i.e. Voluntary or reflexive contraction Is there anything else required to elicit muscle contraction? Besides neural drive, muscles also need energy in order to contract: Energy from sun - to plants - to animals Energy stored in high energy phosphates primarily adenosine triphosphate a.k.a ATP ATP adenosine ~P~P~P adenosine ~P~P P Physiology Review Muscle Fibre Types Type I (Slow Twitch) lower force output slower speed of contraction greater endurance Type II (Fast Twitch) greater force output greater speed of contraction greater fatigability Motor Neurons Motor unit = 1 motor neuron and muscle fibres it innervates ST motor neurons innervate ST muscle fibres, FT neurons innervate FT muscle fibres Overview of Muscular Contraction Neural impulse (AP) travels down motor neuron to neuromuscular junction (motor endplate) AP travels over the sarcolemma and through the T-tubules Calcium is released from Sarcoplasmic Reticulum Molecular cross bridging of Myosin and Actin occurs Muscle contracts Sliding Filament Theory: Myosin heads (cross bridges) grab actin. Actin slides across myosin causing contraction of the sarcomere unit and thus muscle contraction In the absence of a neural impulse: Calcium is taken back up by the SR Interferes with the ability of actin and myosin to form cross bridges Contraction stops Contraction Types Concentric – Muscle shortens as contracts – Muscle force (applied force) > load (resistance) Eccentric – Muscle lengthens as contracts – Muscle force < load Isometric – Muscle length does not change during contraction – Muscle force = load Factors Affecting Force of Contraction Health status Training status Age Gender Genetics Muscle cross sectional area Speed of contraction Joint angle Neural considerations Control of Movement Muscles are driven by neural impulses which can be: - volitional contraction (efferent impulse) - reflexive contraction (afferent impulse) Coordinated movement needs: sensory feedback: - particularly kinesthetic feedback – Vestibular – Proprioceptive - specifically proprioceptive feedback Proprioceptive Receptors: 1. Muscle spindle: Senses stretch in muscle Stretched muscle causes reflexive contraction of muscle being stretched 2. Tendon Receptors: (Golgi tendon organ) Senses muscle tension Tension on tendon causes reflexive relaxation of muscle being contracted 3. Joint Capsule Receptors: Senses compression of the joint capsule Where are we in terms of the class outline? last few lectures of muscle physiology correspond with text Chapters 3 & 4 portions of the chapters were not covered revisit Chpt 3/4 when we discuss Muscular Strength and Endurance The end of this lecture conlcudes the information for misterm 1 Next lecture we will move on to the Energy Systems (Chpt 5) – not on exam...
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