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Anatomy of a Muscle. REC3010 – Human Movement. REC3010 – Human Movement. Muscles in the Body We know that there are 3 different types of muscle in the body Smooth Muscle – Found in the organs Cardiac Muscle – Found in the walls of the heart Skeletal Muscle – Found attached to the skeleton

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anatomy of a muscle

Anatomy of a Muscle

REC3010 – Human Movement

rec3010 human movement
REC3010 – Human Movement

Muscles in the Body

  • We know that there are 3 different types of muscle in the body
    • Smooth Muscle – Found in the organs
    • Cardiac Muscle – Found in the walls of the heart
    • Skeletal Muscle – Found attached to the skeleton
  • Even though all muscle moves and acts in similar fashion, we are going to focus on Skeletal Muscle
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REC3010 – Human Movement

Skeletal Muscle

  • The human body is made up of approximately 600 different skeletal muscles.
    • This number varies depends on what source is used. (350 – 650)
  • The muscle cells
    • Are striated and tubular
    • Have many nuclei
    • Are very long and have many nucleus
    • Are often referred to as fibres, rather than cells
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REC3010 – Human Movement

The Hierarchy of Muscle Structure

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REC3010 – Human Movement

The Hierarchy of Muscle Structure

d) myofibril c) muscle fibre b) muscle fibre bundle a) Muscle belly

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REC3010 – Human Movement

Holding The Muscle Together

  • All muscle components are held together with connective tissue
  • Connective tissue is made up of
    • Epimysium
      • Surrounds entire muscle
    • Perimysium
      • Surrounds bundles of muscle fibers
        • Fascicles
    • Endomysium
      • Surrounds individual muscle fibers
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REC3010 – Human Movement

Holding The Muscle Together

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REC3010 – Human Movement

The Muscle Fibre – Sacromere

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REC3010 – Human Movement

The Muscle Fibre – Thin Myofilament

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REC3010 – Human Movement

The Muscle Fibre – Thick Myofilament

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REC3010 – Human Movement

Movement of the Muscle

  • Text
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REC3010 – Human Movement

Sliding Filament Mechanism

  • Myosin heads attach to actin molecules
    • at binding (active) site
  • Myosin “pulls” on actin, causing thin myofilaments to slide across thick myofilaments, towards the center of the sarcomere
  • Sarcomere shortens, I bands get smaller, H zone gets smaller, & zone of overlap increases
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REC3010 – Human Movement

Sliding Filament Mechanism

  • As sarcomeres shorten, myofibril shortens.
  • As myofibrils shorten, so does muscle fibre.
  • Once a muscle fiber begins to contract, it will contract maximally.
  • This is known as the “all or none” principle.
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REC3010 – Human Movement

Neuromuscular junction

  • Location where the neuron activates muscle to contract
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REC3010 – Human Movement

Muscle Stimulation

  • Muscles require large amounts of interaction with nerves and motor neurons in order to function
  • Involuntary muscle movements are initiated and regulated via the autonomic nervous system
  • Voluntary muscle movements are initiated and regulated via the somatic nervous system
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REC3010 – Human Movement

Autonomic Nervous System

  • Also referred to as the involuntary nervous system
  • Involved with unconscious sensations and actions
  • Controls and regulates the functions of most internal organs and stimuli responses
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REC3010 – Human Movement

Somatic Nervous System

  • Also referred to as the voluntary nervous system
  • Involved with conscious sensations and actions
  • Controls and regulates the functions of most skeletal muscle and movement patterns
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REC3010 – Human Movement

Causing a Muscle to Move

  • Skeletal muscles are made up of thousands of muscle fibers
  • A single motor neuron may directly control a few fibers within a muscle, or hundreds to thousands of muscle fibers
  • All of the muscle fibers controlled by a single motor neuron constitute a motor unit
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REC3010 – Human Movement

Causing a Muscle to Move

  • The size of the motor unit determines how fine the control of movement can be
    • small motor units  precise control
      • e.g. eye muscles - 1:1 muscle/nerve ratio
    • large motor units gross control
      • e.g. hamstring muscle - 300:1 muscle/nerve ratio
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REC3010 – Human Movement

Causing a Muscle to Move

  • Recruitmentis the ability to activate more motor units as more force (tension) needs to be generated
  • There are always some motor units active, even when at rest. This creates a resting tension known as muscle tone, which helps stabilize bones & joints, & prevents atrophy
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REC3010 – Human Movement

Muscle Contraction

  • When skeletal muscles contract, they may produce two types of contractions
    • Isotonic contraction
    • Isometric contraction
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REC3010 – Human Movement

Muscle Contraction

  • Isotonic contraction
    • As tension increases (more motor units recruited), length of muscle changes usually resulting in movement of a joint. The tension (load) on a muscle stays constant (iso = same, tonic = tension) during a movement.
    • Example: lifting a baby, picking up object, walking, etc.
  • Isometric contraction
    • no change in length of muscle even as tension increases. The length of a muscle stays constant (iso = same, metric = length) during a “contraction”
    • Necessary in everyday life to counteract effects of gravity
    • Example: holding a baby at arms length, pushing against a closed door
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