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Chapter 11 The muscular system includes all the skeletal muscles that can be controlled voluntarily. There are about 700 identified skeletal muscles in the human body. A. Muscle Attachment 1. Origin- where a muscle begins a. Generally remains stationary b. Generally proximal 2. Insertion- where a muscle ends a. Generally moveable b. Generally distal 3. Contraction results in the shortening of the distance between the origin & insertion, which causes movement at the insertion end. Flexion Extension Rotation Circumduction Adduction Abduction Pronation Supination Protraction Retraction Inversion Eversion Lateral Opposition Flexion Depression Elevation Prime Mover / Agonist- muscle whose contraction is chiefly responsible for producing a particular movement. A. • Ex. biceps brachii Antagonists- muscle that opposes agonist. B. • Ex. triceps brachii C. Synergist- assists the prime mover D. Fixator- stabilizes agonist to prevent movement. A. Fascicle Organization: 1. Rectus- “straight”- parallel muscles whose fibers run along the long axis of the body 2. Transversus- muscles whose fibers run across the long axis of the body 3. Obliquus- muscles whose fibers run at an angle to the long axis of the body B. Relative Position: 1. Externus- visible at body surface 2. Superficialis- visible at body surface 3. Internus- found beneath the surface 4. Profundus- found beneath the surface 5. Extrinsic- superficial muscles that stabilize an organ 6. Intrinsic- muscles located entirely within the organ C. Structure: 1. Ex. biceps brachii (2 tendons of origin) 2. Ex. quadriceps group (4 tendons of origin) D. Size: 1. Longus / Brevis - long / short muscles 2. Major / Minor - large / small muscles E. Shape: 1. Ex. Trapezius- trapezoid-shaped 2. Ex. Rhomboideus- rhomboid-shaped F. Origin & Insertion: 1. Ex. genioglossus a. Origin: chin “geneion” b. Insertion: tongue “glossus” G. Action: 1. Flexor 2. Extensor 3. …