muscle contraction

• they contract and bring about movement
• types of muscle tissue are skeletal (striated), smooth (non-striated) and cardiac
• When a muscle contracts the actin myofilaments slide over the myosin myofilaments
• The I bands become shorter
• Z lines are closer together so the sacromere is shorter

  actin and myosin overlapping more
• H zone becomes shorter
• 1. ACh is released from the axon terminal of a motor neurone and binds to receptors in the motor end plate. this binding triggers an end-plate potential, which cause san action potential in the muscle cell
• 2. action potential propagates along the sarcolemma and down t tubules
• 3. the action potential triggers Ca2+ release from sarcoplasmic reticulum
• 4. Ca2+ binds to troponin, exposing myosin-binding sites
• 5. the cross bridge cycle begins so the muscle fibre contracts
• 6. Ca2+ is actively transported back into lumen of sarcoplasmic reticulum following the action potential
• 7. tropomyosin blocks myosin-binding sites so relaxing muscle fibres