Overview: Muscle
- Muscle is tissue specialized for contraction, meaning it can shorten or generate force.
- Contractile filaments are protein filaments inside muscle cells that create force by interacting with one another.
- Actin and myosin are the major contractile-filament proteins in muscle cells.
- Striated muscle has visible microscopic stripes produced by the organized arrangement of actin and myosin filaments.
- Smooth muscle lacks cross-striations because its contractile filaments are not organized into sarcomeres.
- Skeletal muscle is striated muscle that usually contracts under voluntary control.
- Cardiac muscle is striated muscle found in the heart and contracts involuntarily.
- Voluntary contraction means contraction can be consciously controlled, as in most skeletal muscle movement.
- Involuntary contraction means contraction occurs without conscious control, as in cardiac muscle and smooth muscle.
- Muscle classification separates muscle into skeletal, cardiac, and smooth types based on structure, control, and organization.
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