*muscles

• Muscles


  are needed to move bones at joints and are made of specialised cells that make themselves shorter (contraction)
• muscles use energy to contract which they get from nutrients, especially glucose.

  energy is released from glucose by respiration and the more you ask your muscles to contract, the more energy and glucose they use.
• Tendons


  muscles produce a strong pulling force when they contract and many muscles are attached to bones by tough cords called tendons.

  the muscle pulls on this when contracting which pulls tthe bone and makes it move at a joint.
• Biceps (one biceps, two biceps) & Triceps



  biceps are the big muscles with two tendons that attach it to the scapula.triceps are the thinner muscle.

  
• Bending the Elbow Joint

  when you bend your elbow, your brain sends an electrical impulse along a neurone, to your biceps muscles.

  the cells in the biceps muscle respond by coontracting, making the muscles get shorter.

  the biceps muscles is firmly fixed to the scapula at one end and the radius at the other end.

  so when the biceps muscle gets shorter, these bones are pulled closer together and the elbow bends

  
• Straightening the Elbow Joint

  when you straighten your arm at the elbow joint muscles can generate a force by getting shorter or contracting as they can only contract and relax.

  the biceps cannot push the arm straight again, so you need another muscle to 'pull the arm straight.

  this is done by the triceps muscle.

  when a muscle is not contracting, it relaxes.

  
• Antagonistic Muscles


  when two muscles work together.

  biceps muscle and triceps muscle work as a team

  • to bend the arm, the biceps contract and the triceps relax
  • to straighten the arm, the triceps contracts and the biceps relaxes.

  when one of them contracts, it moves the bones at a joint in one direction and when the other muscle contracts, it moves the bones in the other direction.