MUSCLES & TENDONS
- Muscles can be categorised into 3 types: Skeletal, cardiac and smooth
Structure:
Sarcomere "the functional unit"
Auxiliary structures:
Auxiliary structures of muscles are the supportive tissues & organs that assist in the function and movement of muscles.
- Tendons
- Aponeuroses: Flat tendons that attach muscles to other muscles or to bones.
- Fascia: Connective tissue that surrounds muscles blood vessels & nerves.
- Bursae: Small fluid-filled sacs located between tendons and bone or between muscles and skin.
- Ligaments: connect bone to bone.
Tendons structure:
Tendons are dense connective tissue that attach muscles to bones, providing stability and transmitting the force generated by muscle contraction to produce movement.
- Muscle contraction is initiated by the signal from CNS
- Release of acetylcholine at the neuromuscular junction
- Causes action potential in muscle fibre
- Triggers the release of calcium ions from sarcoplasmic reticulum
- Calcium ions combine with troponin and tropomyosin uncovers the binding sites on actin and initiates contraction
- Myosin binding sites on actin exposed. Myosin head binds to actin
- Myosin head executes power stroke
- Actin filament slides towards the centre of sarcomere (contraction)
- Signal from CNS stops; calcium ions are pumped back into the sarcoplasmic reticulum
- Tropomyosin masks the binding sites. Filaments pulled back to the original position (relaxation)