1. Antagonistic Muscles D. Crowley, 2007

2. Antagonistic Muscles To know how antagonistic muscles work, and how sports injuries occur

3. Skeleton Our skeleton is made of more than 200 bones: calcium and other minerals make the bone strong but slightly flexible Bone is a living tissue with a blood supply (it can repair itself if broken, and exercise and a balanced diet are important for a healthy skeleton) The skeleton has three main functions: - Supporting the body Protecting some of the vital organs Helping the body move

4. Movement Some bones in the skeleton are joined rigidly together and cannot move against each other - bones in the skull are joined like this Other bones are joined to each other by flexible joints - muscles are needed to move bones attached by joints

5. Antagonistic Muscles Muscles can only pull, and they work by getting shorter (contract) As muscles can only pull, each joint is moved by a pair of muscles - an antagonistic pair Muscles are attached to bones by strong tendons - when a muscle contracts, it pulls on the bone, and the bone can move if it is part of a joint

6. Joints If two bones just moved against each other, they would eventually wear away - this can happen in people who have arthritis To stop this happening, the ends of the bones in a joint are covered with a tough, smooth substance called cartilage, kept slippery by synovial fluid Tough ligaments join the two bones in the joint and stop it falling apart

7. Joints Different types of joint allow different types of movement Hinge joints allow simple movement, the same as a door opening and closing, e.g. knee & elbow joints Ball and socket joints allow movement in more directions, e.g. hip & shoulder joints (the bones cannot move on their own, needing muscles

8. Antagonistic Model Try and make a model of the biceps and triceps The elbow joint lets our forearm move up or down, controlled by two muscles, the biceps on the front of the upper arm, and the triceps on the back of the upper arm: - when the biceps muscle contracts, the forearm moves up when the triceps muscle contracts, the forearm moves down Forearm up Biceps contract (triceps relaxed) Forearm down Triceps contract (biceps relaxed)

9. Sports Injuries What are some common sports injuries? Collar bone breakage / fracture Wrist breakage / fracture Ankle breakage / fracture Plaster casts can be made to support the broken bone, giving it support whilst it heals and is reset in the correct position However, the cast stops the muscle from moving (as a result they are much weaker when the cast is removed)

10. Sports Injuries There are also some more common sports injuries, including: - Pulled muscles - muscle fibres (linking muscle cells together) are stretched or torn (but it is more usual to pull a tendon (tendons attach the muscle to the bone) Sprains - ligaments in a joint are torn (ligaments are cords which attach the bones together) Cartilage injuries - cartilage at the end of the bone gets torn, and breaks up Dislocations - bones in a joint move apart or out of line, so they no longer work