MUSCLES

MUSCLES

1. WHAT DO THEY DO?

   • Produce Movement
     • Shortens
       • Pulls a bone closer to another
   • Maintain Posture
     • Tonic Contraction
       • Only a few muscle fibres shorten
       • Produce NO movement
   • Produce Heat
     • By-product in energy production

2. CHARACTERISTICS

   • Contractibility
     • capable of actively shortening
   • Extensibility
     • stretched without causing damage
   • Elasticity
     • 'elastic band' return to resting length
   • Irritability or Excitability
     • receiving and responding to stimulus

3. TYPES OF MUSCLES

   • SMOOTH
     • involuntary
     • very elastic
     • sustained slow contractions
     • can be very powerful
     • non-striated
     • /Visceral muscles
       • walls of arteries
       • Muscles of digestive system
   • CARDIAC
     • involuntary
     • striated
     • very elastic
     • fatigue resistant
     • Heart wall
   • SKELETAL
     • Voluntary
       • Activated by CNS
     • less elastic
     • fatigue more than other muscle types
     • attach to and move skeleton
     • striated
     • MUSCLE FIBRE TYPES
       • Slow twitch
         • Type 1 fibres
         • small motor units
         • small motor nerve and motor end plates
         • low frequency of firing
         • weak contractions
       • Fast twitch
         • Type 2 fibres
           • Type 2a
             • Fast Oxidative Glycolytic Fibres FOG
               • immediate fibres
             • characteristics of both Type 1 & Type 2
               • adaptable
                 • dependant on training
           • Type 2b
             • Glycolytic fibres
             • large motor nerve and motor plates
             • high frequency of firing
             • strong contractions
             • low endurance
             • high concentration of anaerobic enzymes
         • large
         • anaerobic
         • high force output (strong)
         • low endurance
     • TYPES OF MUSCLE CONTRACTIONS
       • Concentric
         • muscle shortens under tension
       • Eccentric
         • Muscle lengthens under tension
       • Isometric
         • Tension but no change in muscle length
     • FUNCTIONS IN MOVEMENT
       • Agonist
         • Prime mover
         • contracts to produce movement
       • Antagonist
         • opposite to agonist
         • lengthens and yields to movement of the agonist
       • Synergist
         • assists agonist
         • stabilising surrounding joints
           • preventing unwanted movement
       • Fixator
         • assist to stabilise the movement
           • steadying at proximal end of a limb
             • whilst movement occurs at the distal end

4. STRUCTURE

   • Muscle Belly
     • Soft fleshy part
     • Consists of Motor Units
       • = motor nerve
   • Muscle Tendon
     • connects muscle belly - bone
     • dense connective tissue
       • extremely strong