Chapter 11 The Muscular System

1. Chapter 11The Muscular System

2. How Muscles Produce Movement • Produce movement by exerting force on tendons which in turn pull on bones • Generally cross one joint & are attached to bones of joint • One bone remains stationary & other moves • Attachment sites • Origin = attachmt of muscle tendon to stationary bone • Insertion = attachmt of tendon to movable bone • Insertion moves toward origin • Belly of muscle = fleshy portion between tendons • Actions = movements occurring when muscle is contracted

3. Fascicle Arrangement • Effects of fascicle arrangement • Fibers within fascicles are parallel to each other • Fascicles within muscles arranged in 1 of 5 patterns • Parallel • fascicles parallel to long axis of muscle • terminate in tendons @ either end of muscle • ex: stylohyoid • Fusiform • fascicles nearly parallel to long axis • taper toward tendons • ex: digastric muscle • Circular • fascicles arranged in concentric circles • ex: orbicularis oris

4. Fascicle Arrangement • Effects of fascicle arrgmt (ct’d) • triangular • spread over broad area & converge @ thick, central tendon • ex: pectoralis major • pennate • short fascicles; tendon extends entire length of muscle • 3 subcategories • unipennate = fascicles on one side of tendon (extensor digitorum longus) • bipennate = fascicles on both sides of centrally positioned tendon (rectus femoris) • multipennate = fascicles attached obliquely from a # of directions to several tendons (deltoid)

5. Fascicle Arrangements • A contracting muscle shortens to about 70% of its length • Fascicular arrangement represents a compromise between force of contraction (power) and range of motion • muscles w/ longer fibers have greater range of motion • short fiber can contract as forcefully as a long one

6. How Muscles Produce Movement • Coordination within muscle groups • movement = result of antagonistic muscle pairs @ joints • prime mover (agonist) = muscle that contracts to cause action • antagonist stretches & yields to prime mover • within a pair of muscles, roles of antagonist/prime mover switch with movement produced • ex: biceps/triceps brachii in flexion/extension of elbow

7. Naming Skeletal Muscles • Names of most skeletal muscles are based on several types of characteristics • Characteristics may be reflected in name of muscle • direction of fibers • size of muscle • major = large  pectoralis major • minimus = smallest  gluteus minimus • shape of muscle • delt = triangular  deltoid • rhomb = diamond  rhomboid • action of muscle • Adduction of thigh  adductor longus • number/site of origins • biceps brachii/femoris: 2 sites of origin • triceps brachii: 3 sites of origin • quadriceps femoris: 4 sites of origin