The Muscular System

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The Muscular System

• Chapter 11
• Anatomy and Physiology
• Mr. Knowles
• Liberty Senior High School

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You cant talk about the physique without a
little physics first!
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The Physics of the Muscular System

• Tension- an active force applied to some object
  that requires energy. Ex. People pulling on a
  rope, the PULL is the tension.
• When muscle cells contract, they PULL on the
  connective tissue, tendons.

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The Physics of a Physique

• Compression- another active force that PUSHES an
  object AWAY from the source.
• Resistance- a passive force that OPPOSES movement
  that depends on weight, shape, friction, etc.

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The Laws of Muscle Physics

• When the Tension gt Resistance Movement.
• The object is pulled toward the source of the
  tension. Muscle cells can ONLY shorten and
  generate tension, NOT lengthen to generate
  compression.

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Tension and Muscles

• The amount of tension a muscle can generate is
  related to the number of resting sarcomeres it
  has. The more sarcomeres ? the more tension.
• Some muscles contract and pull against tendons or
  sheets of collagen called aponeuroses at their
  ends.

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Structure and Function of Muscles

• Structure Function
• Some work across joints ? movement.
• Others support soft tissue ?form slings.
• Still others completely
• encircle openings ?sphincters.

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Organization of Skeletal Muscle Fibers

• Muscle fibers form bundles called ????
  Fascicles!
• The fibers within a single fascicle are parallel
  BUT the organization of the fascicles,
  themselves, can vary.

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Four Patterns of Fascicle Organization . . .

• Parallel Muscles
• Convergent Muscles
• Pennate Muscles
• Circular Muscles

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Parallel Muscles

• The fascicles are parallel to the long axis of
  the muscle. Most common type of muscle.
• The muscle is spindle-shaped with a central body
  (belly) or gaster.
• Example biceps brachii

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Parallel Muscles
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Convergent Muscles

• The muscle fibers are based over a broad area,
  but all the fibers come together at a common
  attachment site.
• Fibers spread out like a fan
• Example pectoralis major

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Convergent Muscles
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Pennate Muscles

• The fascicles form a common angle with the
  tendon.
• Contracting pennate (feather) muscles do not move
  their tendons as far as parallel but contain more
  muscle fibers which produces more tension.

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Three Types of Pennate Muscles

• Unipennate extensor digitorum
• Bipennate rectus femoris
• Multipennate deltoid

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Unipennate extensor digitorum
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Bipennate rectus femoris
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Multipennate deltoid
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Circular Muscles

• Fibers are concentrically arranged around an
  opening or recess. When the muscle contracts,
  the diameter of the opening decreases.
• Guard entrances exits of internal passageways
  sphincters.
• Example orbicularis oris

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Circular Muscles
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Tension of a Muscle

• Related to the length and number of the resting
  sarcomeres it has.
• The tension a muscle provides can change through
  the movement.
• Ex. The biceps brachialis through a curl.

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Muscle Work Together

• Complex movements require several muscles to work
  together for efficiency.
• Large limb muscles may not reach maximum tension
  until part way through the motion. Need smaller
  muscles to assist.
• At the start of the movement, smaller muscles
  produces maximum tension, while the larger muscle
  produces minimum tension until much later.

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General Names of Muscles

• Prime Mover or Agonist- a muscle whose
  contraction is mainly responsible for the
  movement. Ex. Biceps.
• Antagonists- are prime movers whose actions
  oppose a particular agonist. Ex. Triceps to the
  biceps.
• Synergist- usually smaller muscles that assist
  the prime mover in performing an action usually
  important at the beginning.

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Muscle Terms

• Every muscle has a beginning- origin and an end-
  insertion. The movement produced is the action.
• Origins- remains stationary during the movement
  usually proximal to the insertion.
• Insertions- changes its position during the
  movement.

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Muscle Terms

• Action- is the motion produced by the contraction
  of the muscle(s). Usually across a joint.

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Naming Muscles

• Some names refer to fascicle organization
• Rectus- straight, parallel muscles to the long
  axis of the body.
• Often combined with a term describing precise
  location
• Rectus abdominis, Rectus femoris.

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Naming Muscles

• Directional terms
• Transversus or Obliquus- fibers that run at an
  oblique angle to the long axis of body.
• Lateralis- lateral muscles.
• Medialis- more medial muscles.

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Naming Muscles

• Location names may specify a certain region of
  the body. Ex. Temporalis- head, Brachialis-arm.
• Relative Position muscles close to the
  surface-externus, those deeper-internus.
• Structure biceps- has two heads, triceps- has
  three , and quadriceps- has four.

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Naming Muscles

• Shape Trapezius- trapezoid, Deltoid-triangular,
  Orbicularis-circle.
• Size larger muscles- Major, smallest- Minor,
  long muscles-Longus.
• Action based on the motion flexor, extensor,
  abductor, adductors.

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Other Location Names

• Oris- refers to the mouth.
• Oculi- refers to the eye.

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The Muscle Insertion and Origin Activity
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