The Muscular System Muscle tissue overview All muscle

The Muscular System

Muscle tissue overview • All muscle cells are elongated, thus, all muscle cells, regardless of type, are called muscle fibers • The ability of muscle to shorten or contract depends on 2 types of myofilaments • Prefix: - myo/mys: muscle - Sarco: flesh

Muscle Types Muscle type: Body location: Cell Shape: Regulation of Contraction: Contraction Speed/Rhythmic: skeletal muscle attached to bone; single, very long cylindrical, multinucleate, nucleate striations; striations cardiac muscle smooth muscle walls of heart; walls of hollow organs; branching chains, uninucleate striations; striations Single, spindles, uninucleate no striations; striations involuntary, involuntary ner- vous system voluntary, voluntary nervous involuntary, vous system controls; controls, hormones, controls, hormones; chemicals, stretch; Slow to fast/no; Slow/yes; Very slow/some

Skeletal Muscle • Key words: Skeletal, Striated, Voluntary

Skeletal Muscle • Skeletal muscle fibers: are packed into the organs called skeletal muscles that attach to the body’s skeleton • Skeletal muscle fibers are cigar-shaped, multinucleate cells, and are the largest of the muscle fiber types • It is also known as striated muscle because its fibers appear to be striped • It is also known as voluntary muscle because it is the only muscle type subject to conscious control • Skeletal muscle tissue can contract rapidly and with great force, but it tires easily and must rest after short periods of activity

Connective tissue wrapping • Each muscle fiber is enclosed in a delicate connective tissue sheath called an endomysium • A bundle of muscle fibers called a fascicle are surrounded by a connective tissue called the perimysium • A bundle of fascicles are surrounded by a connective tissue called the epimysium

Tendons • The epimysia blend into the strong, cordlike tendons • Tendon connects muscle to bone • Tendons provide durability and conserve space

Cardiac Muscles • Key words: Cardiac, striated, uninucleate, involuntary, heart

Cardiac Muscle • Is found only in the heart • Cardiac muscle is like skeletal muscle in that it is striated and like smooth muscle in that it is involuntary and cannot be consciously controlled by most of us • Cardiac muscle fibers are branching cells joined by special junctions called intercalated disks

Cardiac Muscle • The cardiac muscle is cushioned by small amounts of soft connective tissue and arranged in spiral or figure 8 bundles • Cardiac muscle usually contracts at a fairly steady rate set by the heart’s pacemaker, but can also be stimulated by the nervous system

Smooth Muscle • Key words: smooth, visceral, involuntary, uninucleate, non-striated

Smooth Muscle • Smooth muscle has no striations and is involuntary • Found in the walls of hollow visceral organs such as the stomach, urinary bladder etc.

Smooth Muscle • Smooth muscle cells are arranged in 2 layers: - One layer runs circularly - The other running longitudinally • The two layers alternately contract and relax, and this changes the size and shape of the organ, resulting in the movement of food, wastes, etc.

4 Muscle Functions producing movement walking; swimming; move eyes; Smile Frown move fluid; move food. maintaining posture allow you to stand up straight against the force of gravity. stabilizing joints help reinforce bones that do not articulate well with the skeleton; Ex. : shoulder generating heat ATP used to cause muscles to contract; ATP energy is lost as heat; This helps maintain body temperature.