Muscles and Movement

Muscles and Movement

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

Muscles

• 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…