Muscles and Movement

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Muscles and Movement

1. Describe the structure of a muscle fibre and explain the differences between fast and slow twitch fibres


  • Antagonistic pairs of muscles pull in opposite directions
  • Extensor muscles contract to cause joint extension. 
  • Flexor muscles contract to reverse the movement of the extensor muscles. 
  • Muscles bring about movement at a joint

Joint Structure

  • Tendons join the muscle to the bone.
  • The muscle is attached to the bone by tendons, and is on the outside of the joint. 
  • The ligament is on the inner side of the muscle and attaches bone to bone. It is strong and flexible.
  • The fibrous capsule encloses the joint and is between the ligament and the synovial membrane.
  • The synovial membrane is protected by the fibrous capsule and secretes synovial fluid.
  • Synovial fluid is secreted by the synovial membrane and acts as a lubricant for the joint.
  • Cartilage protects the bones within the joints and absorbs synovial fluid as well as acting as a shock absorber.
  • Cartilage pads give additional protection. 

Muscle Fibres

  • Bundles of muscle fibres make up muscles. 
  • Myofibrils make up muscle fibres.
  • Myofibrils are made up of contractile units known as sarcomeres.
  • Sarcomeres are made from thin filaments (actin) and thicker filaments (myosin). 
  • In contraction, the actin


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