Skeletal muscle contraction

• Neurotransmitter 


  A chemical produced and secreted by a neuron which transmits the nerve impulse across the synaptic cleft to the muscle fibre.
• All or none law


  Depending on whether the stimulus is above a threshold, all muscle fibres will give a complete contraction or no contraction at all.
• Motor neurone 


  A nerve cell which conducts a nerve impulse to a group of muscle fibres.
• Motor unit 


  A motor neuron and the muscle fibres stimulated by its axon
• Action potential 


  Positive electrical charge inside the nerve and muscle cells which conducts the nerve impulses down the neurone and into the muscle fibre.
• Slow oxidative muscle fibres


  A type of muscle fibre rich in mitochondria, myoglobin and capillaries which produces a small amount of force over a long period of time.
• Fast glycolytic muscle fibres


  A type of muscle fibre rich in phosphocreatine which produces maximal force over a short period of time.
• Phosphocreatine 


  A high energy compound stored in the muscle cell used as a fuel for very high intensity energy production.
• Mitochondria 


  A structure in the sarcoplasm responsible for aerobic energy production.
• Myoglobin


  A protein in the muscle responsible for transporting oxygen to the mitochondria.
• Aerobic work 


  Low intensity, long duration, exercise in the presence of oxygen.
• Anaerobic work

  High intensity, short duration, exercise in the absence of oxygen.
• Work: relief ratio


  The volume of relief in relation to the volume of work performed.
• Joint


  An area of the body where two or more bones articulate to create human movement
• Ligament 


  A tough band of fibrous, slightly elastic connective tissue that attaches bone to bone
• Articular cartilage 


  Smooth tissue which covers the surface articulating bones to absorb shock and allow friction- free movement
• Flexion 


  Movement which decreases the angle at a joint, usually to the front of the body
• Extension 


  Movement which increases the joint angle, usually to the back of the body
• Dorsi-flexion 


  Movement at the ankle joint as the toes move up
• Plantar flexion 


  Movement at the ankle joint as the toes move down
• Abduction 


  Movement of the limbs away from the midline of the body
• Adduction 


  Movement of the limbs towards the midline of the body
• Horizontal extension 


  Movement of the limbs away from the midline of the body parallel to the ground
• Horizontal flexion 


  Movement of the limbs towards the midline of the body parallel to the ground
• Rotation 


  Movement whereby articulating bones turn about their longitudinal axis in a screwdriver action
• Tendon


  A fibrous connective tissue that attaches a muscle to bone
• Agonist 


  A muscle responsible for creating movement at a joint. Also known as the prime mover.
• Antagonist

  A muscle that opposes the agonist providing a resistance for coordinated movement
• Fixator 


  A muscle that stabilises one part of a body while another moves
• Antagonistic muscle action


  Paired muscle action. As the agonist muscle shortens to create movement, the antagonist lengthens to coordinate the action
• Isotonic contraction 


  Muscular contraction which changes length during its contraction. This can occur in two ways: concentric and eccentric contraction
• Concentric contraction 


  Muscular contraction which shortens while producing tension
• Eccentric contraction 


  Muscular contraction which lengthens while producing tension
• Isometric contraction 


  Muscular contraction which stays the same length while producing tension
• Delayed onset muscle soreness 


  Pain and stiffness felt in the muscle which peaks 24-72 hours after exercise, associated with eccentric muscle contractions
• Movement analysis 


  Analysis of the type and cause of bodily movement, including knowledge of the joint type , articulating bones, movement pattern, agonist and antagonist muscle action and contraction type
• Articular / hyaline cartilage

  This covers the ends of the bones at a joint and is there to prevent friction between the articulating bones
• Joint capsule

  A tough fibrous layer of tissue encasing the joint, which is present to protect and strengthen the joint
• Synovial membrane

  The inner layer or lining to the joint capsule, which nourishes the articular cartilage and prevents friction
• Synovial fluid

  Fluid that fills the joint capsule, which nourishes the articular cartilage and prevents friction