Types of Muscle
- Smooth
- Does not require conscious
- Found in walls of internal organs (excluding heart)
- g. Intestines, blood vessels
- Cardiac
- Does not require conscious
- Found only in the heart
- Skeletal (striated/striped/voluntary)
- Requires conscious
- Controls mobility
- g. biceps, triceps
Skeletal Muscle
- Skeletal muscle is attached to bones via tendons
- Ligaments attach bones to another bone
- Pairs of skeletal muscles work antagonistically at the joints
- The bones act as levers, allowing the muscles to pull against them
- Skeletal muscle is made up of bundles of muscle fibres
- Cell membranes of muscle fibre cells is the sarcolemma
- Transverse Tubules are the folds of the sarcolemma inwards across the muscle fibre and into the sarcoplasm (cytoplasm)
- Transverse tubules help to spread electrical impulses through the sarcoplasm so all parts of the muscle fibre is reached equally
- Sarcoplasmic reticulum is a network of internal membranes which through the sarcoplasm
- Sarcoplasmic reticulum stores and releases Ca2+
- There is high number of mitochondria to provide adequate ATP
- Muscle fibres are multinucleate (many nuclei)
- They have lots of myofibrils
- Long cylindrical organelles which are made up of proteins which are specialised for muscle contraction
Myofibrils
- Contain bundles of thick and thin myofilaments which can slide past each other
- Thick myofilament is Myosin (dark band)
- Thin myofilament is Actin (light band)
A band) some overlapping thick and thin filaments
I band) Only contains (thin) actin filament
H Zone) Only contains myosin filaments
Z line) End of each sarcomere
M line) Middle of the myosin filament
Sliding Filament Theory
- Muscle contraction occurs due to sliding filaments
- Myosin and actin filaments slide over one another to make the sarcomere contract
- Myofilaments do no contract.
- The larger amount of simultaneous sarcomere contractions results in the muscle fibres and myofibrils contracting
- Sarcomeres return to original length after on relax