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Chapter 8
Muscular System
Term | Definition |
---|---|
Skeletal Muscle | also called striated or voluntary muscle; has crosswise stripes or striations; contractions can be voluntarily controlled |
Cardiac Muscle | composes bulk of heart; Cardiac fibers are branched; has dark bands called intercalated disks |
Nonstriated muscle, or involuntary muscle | also called smooth or visceral muscle; lacks striations when seen under a microscope, appears smooth; Found in walls of hollow structures like the digestive tract, blood vessels, etc |
Regions of a Skeletal Muscle | Origin, Insertion, Body |
Bursae | small synovial-lined sacs containing a small amount of synovial fluid; located between some tendons and underlying bones |
myosin | thick myofilaments |
actin | thin myofilaments |
sarcomeres | separated from each other by dark bands called Z lines |
Prime Mover | mainly responsible for producing a given movement |
Synergist | helps the prime mover produce a given movement |
Antagonist | opposes the action of a prime mover in any given movement |
Neuromuscular Junction (NMJ) | point of contact between a nerve ending and the muscle fiber |
Motor Unit | combination of a motor neuron with the muscle fibers it controls |
Threshold Stimulus | Minimal level of stimulation required to cause a muscle fiber to contract |
"all of none" | Once stimulated by a threshold stimulus, a muscle fiber will contract completely |
Flexion | Decreases an angle |
Extension | Increases an angle |
Abduction | Away from the midline |
Adduction | Toward the midline |
Rotation | Around an axis |
Circumduction | Move distal end of a part in a circle |
Supination & Pronation | Hand positions that result from twisting |
Dorsiflexion & Plantar Flexion | Ankle movements (upward and downward foot movement) |
Inversion & Eversion | Ankle movements (sideways) |