Chapter 11 The Muscular System

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Chapter 11The Muscular System
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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

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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 _at_ 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

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Fascicle Arrangement

• Effects of fascicle arrgmt (ctd)
• triangular
• spread over broad area converge _at_ 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)

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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

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How Muscles Produce Movement

• Coordination within muscle groups
• movement result of antagonistic muscle pairs _at_
  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

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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