movement of the entire animal as a whole
- hard structures inside the body.
- made from cartilage and bone
- made up of cells in a hard extracellular matrix of calcium phosphate, with small amounts of calcium carbonate and protein fibers.
- meet at locations called articulations or joints, so they can swivel, hinge, or pivot.
bands of tough, fibrous connective tissue.
the muscle that swings two long bones in an arc toward each other
the muscle that straightens bones out
- a long, thin muscle cell.
- muscle fibers contain many myofibrils
- alternating light-dark units that repeat down the length of a myofibril.
- they shorten as the cell contracts and lengthen when the cell is relaxed.
the theory that muscle movements are caused by two types of long filaments: thick filaments and thin filaments, that slide past one another during contraction.
- composed of two coiled chains of the globular protein actin.
- one end of each thin filament is bound to a structure called the Z disk which forms the wall of the sarcomere.
- composed of multiple strands of a long protein called myosin. anchored to the middle of the sarcomere.
- myosin is the site of active movement
- the state an animal enters when myosin and actin are locked together shortly after the animal dies
- because ATP is unavailable in dead tissue, it suggests that ATP is involved in getting myosin to release from actin
Since ATP is always available in living muscles, how do our muscles ever stop contracting and relax?
- Thin filaments contain 2 proteins called tropomyosin and troponin. They work together to block the myosin binding sites on actin so that the thick and thin filaments can't slide past each other.