1. 1 Chapter 11 The Muscular System

2. 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. 3 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 Fascicle Arrangement

4. 4 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) Fascicle Arrangement

5. 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. 6 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 How Muscles Produce Movement

7. 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