The Neuromuscular System

Created by: ErinSkoyles
Created on: 03-02-17 20:25

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The Neuromuscular System
- Anatomy
  - Central Nervous System
    - Automatic (Involuntary)
      - control and regulation of main organs
    - Somatic (voluntary)
      - Cerebellum control of the skeletal muscle
  - Muscle Motor Unit
    - Muscles fibres
      - Motor neurones
    - Motor neuron stimulated by impulse
      - Connecting fibres activated
        All or None law
  - Skeletal Muscle
    - Myofibrils
      - Myofilaments
        Made from actin and myosin
        Motor proteins that move along actin filaments
        
        Polymer- essential for cellular function
        Mobility and contraction of cells
      - Sarcomere
        Basic unit of striated muscle tissue
    - Fibres groups are called Fascicles
      - form muscle
- Motor Neurone
  - Cell body
    - Receptive to stimuli from other neurones
  - Dendrites
    - Branched processes that receive stimuli from other sensory organs or neurones
  - Axon
    - Conducts nerve impulses to other cells
  - Myelin Sheath
    - Electrically insulates the nerve cell
  - Nodes of Ranvier
    - Gaps in the sheath which allow for action potential jumps
  - Axon Terminal
    - Branches to skeletal muscle for stimulation of fibres
  - Synaptic Bulb
    - Contains neurotransmitter substances
- Pathway of a nerve impulse
  - Motor cortex
    - Planning, control and execution of voluntary movement
    - Cerebellum
      - Brain stem
        Involved in heart rate and breathing rate
        
        Spinal Cord
        Motor Neuron
        Motor Unit
        Axon Terminals at neuromuscular junctions
        Muscle Fibres
        Contraction
        If action potential reaches threshold
        Action Potential is received
        
        All or None law
        
        Action Potential is received
        
        Motor Units work together to coordinate the contractions of a single muscle
      - Coordinates and regulates muscular activity
- Muscle Fibre Types
  - Long cylindrical bundles
  - Mixture of different fibre types
    - Proportion varies as it is genetically determined
  - Slow Twitch (Type 1)
    - Aerobic exercise
      - High mitochondrial density
    - Uses oxygen to produce small amounts of tension over long periods of time
    - Resistant to fatigue
      - Slow contraction speed
        110m2
    - Red in colour
      - Myoglobin
    - Endurance and postural activities
    - Small motor neurone size
      - Low conduction capacity
    - Large capillary density
    - Low glycogen stores
      - High triglyceride stores
  - Fast Oxidative Glycolytic (Type IIa)
    - Anaerobic capacity
    - High power contraction
      - Short periods of time
      - Speed 50m2
    - Low resistance to fatigue
    - White
      - Low levels of myoglobin
    - More resistant to fatigue than type IIb
      - Less force
    - 200m swim and 800m
    - High glycogen stores
    - High motor neurone conduction capacity
    - High myosin ATPase/glycolytic enzyme activity
  - Fast Twitch Glycolytic (Type IIb)
    - Greatest Anaerobic capacity
    - Largest amount of force
      - Larger motor neuron carrying impulse
    - Very poor resistance to fatigue
    - Sprinter, shotputter and weightlifter
    - Small capillary density
    - High glycogen stores
    - Low triglyceride stores
- Muscle Fibre Recruitment
  - Control Contraction
    - Cerebellum activates motor neurones
      - Activates all of the muscle fibres
        Different fibre groups can be fired at different times- TWITCH
  - Multiple Wave Summation
    - Repeated firing of muscle fibres
      - More sustained contraction
      - ^ ^ ^ ^ ^
    - Contractile strength is greater if the motor unit is continuously activated by a stimulus
      - Activated before completely relaxed
  - Tetanic Contraction
    - As the force produced grows in a series of waves
      - The stimuli become so fast that there is no relaxation
    - Usually power based activities
      - Quick sharp movements
    - If no rest then the muscle locks up
    - ^^^^^^^^^
  - Spatial Summation
    - Motor unit are activated at slightly different times
      - Different groups are fired
    - Staggering contraction and relaxation
      - Sustain a contraction over a long period of time
        Fatigue resistant
    - ^ > < ^ < > ^
  - Factors affecting contractile strength
    - Stimulus
      - Increasing stimuli frequency increases the contraction
    - Location
      - Bigger muscles have more motor units per muscle and this creates delicate and controlled contraction
    - Fibre Type
      - Slow twitch fibres - low intensity.
      - Fast Twitch fibres- High intensity
- Sliding Filament Theory
  - 1. Calcium Ions are released from the sarcolemma T Tubules
  - 2. Calcium ions react with TROPONIN to release the BINDING SITES on the ACTIN FILAMENTS
    - 3. MYOSIN heads attach to the BINDING SITES
      - 4. MYOSIN HEADS pulls on the ACTIN filament which pulls the MYOSIN to the midline of the sarcomere
        5. ATP detaches the MYOSIN heads from the BINDING SITES
        6. ATP re-energises the MYOSIN head so tHat the MYOSIN head can reattach to the BINDING SITE on the ACTIN FILAMENT
        7. Calcium ions return to sarcoplasmic reticulum and MYOSIN head shorten with BINDING SITES closing
        TROPOMYOSIN blocks sites
    - Changes shape
      - Displace TROPOMYOSIN
  - Actin- Thin Filaments
  - Myosin- Thick Filaments
  - A- Band
    - Length of Myosin
  - I- Band
    - End to End of the Myosin (Actin only)
- Immediate Responses to exercise - Warm Up
  - Quicker response time
  - Recruitment of additional fast twitch motor units
  - Better co-ordinated and strength of muscle actions
  - Rentention of muscle action (rehearsal)
    - Reduce antagonistic response- fluent
  - Neural activation and action potential
  - Reduced risk of injury
- Long term adaptations
  - Anaerobic
    - Fast twitch hypertrophy
      - Faster recruitment
    - Increased number of myofibrils
    - Increase in actiin and myosin strength
    - Increased lactate tolerance
      - Reduce OBLA (Onset of blood lactate)
    - Toughening of proprioreceptors
    - Reduced DOMS
  - Aerobic
    - More myoglobin
    - Bigger mitochondria
    - Increased oxidative enzymes
    - Increased glycogen stores
    - Faster recruitment of slow twitch fibres
    - Conversion of type iib to type iib
    - Reduced DOMS

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The Neuromuscular System

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