Why its important
Three types of muscle tissue
show the structure of a sarcomere, including Z lines,actin filaments, myosin filaments with heads, and the light and dark bands.
- The H zone is the area only occupied by the thick filaments (myosin)
- The I bands (light) are the regions occupied by only thin filaments (actin)
- The A bands (dark) are the regions occupied by both filaments (overlap)
- The Z lines represent the extremities of a single sarcomere
Explaining how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of act in and myosin filaments and the use of ATP.
- An action potential from a motor neuron triggers the release of Ca2+ ions from the sarcoplasmic reticulum
- Calcium ions expose the myosin heads by binding to a blocking molecule (troponin complexed with tropomyosin) and causing it to move
- The myosin heads form a cross-bridge with actin binding sites
- ATP binds to the myosin heads and breaks the cross-bridge
- The hydrolysis of ATP causes the myosin heads to change shape and swivel - this moves them towards the next actin binding site
- The movement of the myosin heads cause the actin filaments to slide over the myosin filaments, shortening the length of the sarcomere
- Via the repeated hydrolysis of ATP, the skeletal muscle will contract
2 Major disorders that occur in this system
Other common disorders are muscular dystrophies and metabolic muscle disorders. Muscular dystrophy affects muscle fibers. Metabolic muscle disorders interfere with chemical reactions involved in drawing energy from food.Neuromuscular junction disorders impair the transmission of nerve signals to muscles.