Muscle and Muscle Tissue - PowerPoint

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					Muscle and Muscle
Tissue
Chapter 9 & 10
Muscle Tissue
•3 Types                        •Differ in:
  •Smooth – smooth muscle          •Structure
  •Skeletal – skeletal muscle      •Function
  •Cardiac – cardiac muscle        •Location
                                   •Means of activation
Functions of Muscle
 • Skeletal
   • responsible for locomotion
   • Posture, stabilize joints, generate heat
 • Cardiac
   • responsible for movement of blood
 • Smooth muscle
   • helps maintain blood pressure, and squeeze
     or propel substances through organs
Functional Characteristics of Muscle
Tissue
    • Excitability (irritability) – the ability to
       receive and respond to stimuli

     • Contractility – ability to shorten forcibly

     • Extensibility – ability to stretch or extend

     • Elasticity – ability to recoil and resume
       original resting length
Muscle Tissue Similarities
•Muscle Terminology            •Skeletal and smooth
  •Sarcolemma – muscle         muscle are elongated and
  plasma membrane              are called muscle fibers
  •Sarcoplasm – cytoplasm of
  a muscle cell                •Muscle will contract based
  •Prefixes:                   on 2 types of
     •Myo                      microfilaments
     •Mys all mean muscle        •Actin
     •Sarco                      •Myosin
Skeletal Muscle Tissue
 •   Muscle that attaches to and covers bone
 •   Creates motion
 •   Has obvious striations (stripes)
 •   Is voluntary
     • most of the time
 • Contracts rapidly but tires easily
 • Extremely adaptable and can exert forces
     ranging from a fraction of an ounce to
     over 70 lbs.
Skeletal Muscle
• Each muscle is an organ
  • Consisting of
    • Blood vessels
    • Nerve fibers
    • Connective tissues
       • Endomysium – fine sheath of connective tissue composed of
         reticular fibers surround each muscle fiber
       • Perimysium – fibrous connective tissue that surrounds a group of
         muscle fibers called fascicles
       • Epimysium – an overcoat of dense regular tissue that surrounds
         the entire muscle
Skeletal Muscle
Skeletal Muscle
•Nerve & Blood Supply         •Attachments
  •Each muscle has              •Most muscles are attached
     •One nerve                 to bones in 2 places
     •One artery                   •Attach either
     •One or more veins                •Directly – epimysium of the
                                       muscle is fused to the bone
  •Each muscle fiber has               •Indirectly – connective
     •One nerve controlling            tissue wrappings extend
     contraction                       beyond the muscle as a
                                       tendon
  •Muscles need
     •Oxygen and nutrients
     •Waste elimination
Microscopic Anatomy
• Muscle Fibers:
  • Each fiber is long, cylindrical with multiple nuclei
    just beneath sarcolemma
  • Each fiber has unique oxygen-binding proteins
    called myoglobin
Myofibrils
•Muscle fibers are
made up of densely
packed myofibrils
  •Rod like contractile
  elements

  •Myofibrils are what
  gives muscle its
  striated appearance
     •Because it makes
     perfect Dark A Bands
     and Light I Bands
Sarcomere
•Myofibrils are
composed of the
sarcomeres
   •Smallest contractile
   unit of the muscle
   •Composed of
   myofilaments
      •Thick – myosin (entire A
      band)
      •Thin – actin (across I
      band and partway into A
      band)
      Z disc – connects
      myofibrils to one another
Sarcoplasmic Reticulum (SR) and T
Tubules
 •SR – an elaborate,   •T Tubules –         elongated
 smooth ER that        tubes that penetrate the cell’s
                       interior at the A – I band junction
 mostly runs               •Conduct impulses to the
 longitudinally and        deepest parts of the muscle
                           •Part of the SR
 surrounds each
 myofibril
 •Functions in
 regulation of
   calcium levels
Skeletal Muscle Contraction
 •Sliding Filament Model of contraction:
   •Thin Filaments slide past Thick filaments (filaments overlap
   more than before)
   •Causes the muscle to shorten
Contraction
• In order to contract a skeletal muscle must:
  • Be stimulated by a nerve ending – motor neurons
     • The size of the muscle relates to the size of the motor
      neuron
  • Receive an electrical impulse along sarcolemma and
    T tubules
  • Have a rise in Ca2+ levels (final trigger for muscle
    contraction)
Stages of Muscle Contraction
 • Cross Bridge formation – myosin cross
   bridge attaches to actin filament
 • Working (power) stroke – myosin pulls
   actin filament toward M line
 • Myosin releases actin filament
   • ATP attaches to myosin and the cross bridge
     is broken
 • “Cocking” of the myosin – energy for
   hydrolysis of ATP cocks myosin into high-
   energy position
Types of Contractions
•Isometric contraction         •Isotonic Contraction
  •Increasing muscle tension     •Decreasing muscle length
     •Muscle doesn’t shorten        •Muscle shortens during
     during contraction             contraction
Muscle Tone
• Constant, slightly contracted state of all
  muscles, which does not produce active
  movement
• Keeps muscles firm, healthy, and ready to
  respond to stimuli
Muscle Metabolism: Anaerobic
Glycolysis
• When muscle contractile activity reaches 70%
 of the maximum
  • Bulging of the muscle compresses blood vessels
  • Oxygen delivery is impaired
  • Pyruvic acid is converted to lactic acid
    • Causes muscle soreness
Muscle Fatigue
• The muscle is in a state of physiological
 inability to contract
  • Occurs when:
     • ATP production fails to keep pace with ATP demand
     • Lactic acid accumulates in the muscle
Heat Production
• Only 40% of the energy released in muscle
 activity is actually used in the work

• The remaining 60% is given off as heat
Cardiac Muscle
• Found only in the heart
• Striated
• Involuntary
• Contracts at a steady rate due to the heart’s
  pacemaker
• Changes beat based upon body’s needs
    • Running – speeds up
    • Sleeping – slows down
Smooth Muscle
• Found in the walls of hollow organs
  • Stomach, urinary bladder, vessels
• Forces food and other substances through
 internal body channels
  • Responsible for peristalsis
• Not striated
• Involuntary
Smooth Muscles
• Made up of small spindle –shaped fibers

• Lacks the coarse connective tissue sheath of skeletal
  muscle
  • But has endomysium

• Organized into 2 layers
  • Longitudinal – muscle fibers run parallel to the long axis of
    the organ
  • Circular – fibers run around the circumference of the organ

• Has same contractile mechanism as skeletal
Peristalsis
• Peristalsis – alternating contraction and
 relaxation of smooth muscles that mix and
 squeeze substances through the hollow organs

• Caused by:
  • Longitudinal layer of smooth muscle contracts
     • When the longitudinal layer contracts the organ elongates
Microscopic Smooth Muscle
• SR is less developed

• T tubules are absent

• Plasma membrane has pouch like infoldings
 called caveoli

• No visible striations (no sarcomere)
Microscopic
              •Thin and Thick filaments
              are present
                •Ratio of thick to thin
                filaments is much lower
                than skeletal
                •Arranged diagonally –
                causing smooth muscle to
                contract in a corkscrew
                manner
Smooth Muscle
• Some unique features of smooth muscle
  • Smooth muscle is very tone

  • Slow, prolonged contractile activity

  • Low energy requirements

  • Response to stretch
Response to Stretch
• Smooth muscle exhibits a phenomenon called stress-
  relaxation response in which

  • Smooth muscle responds to stretch briefly and then adapts
    to new length

  • The new length, however, retains its ability to contract

  • This enables organs such as the stomach and bladder to
    temporarily store contents
Hyperplasia
• Hyperplasia – is the ability of smooth muscle to
 divide and increase in number

• Exhibited in women
  • At puberty, the estrogen stimulates the synthesis of
    more smooth muscle, causing the uterus to grow to
    adult size
  • At pregnancy, estrogen stimulates uterine growth to
    accommodate the increasing size of the growing
    fetus
Types of Smooth Muscle
• Single Unit

• Multiunit
Single Unit
• Commonly called visceral muscle

  • Contracts rhythmically as a unit

  • Arranged in opposing sheets and exhibit stress-
   relaxation response
Multiunit
•   Structurally independent muscle fibers
•   Have a rich nerve supply
•   Responds to neural stimuli
•   Found:
    •   Large airways to lungs
    •   In large arteries
    •   In arrector pilli muscle and attached to hair follicles
    •   Internal eye muscles
Muscular Dystrophy
• Muscular Dystrophy –
  • Group of inherited muscle destroying diseases
   where the muscles enlarge due to fat and
   connective tissue deposits, but muscle fibers
   atrophy and degenerate
Muscular Dystrophy
• Most common type: Duchenne Muscular
 Dystrophy (DMD)
  • Inherited, sex-linked trait, carried by women and
      exhibited in men (1/3500)
  •   Diagnosed between age 2-10
  •   Victims become clumsy and fall
  •   Progress from extremities upward
  •   Usually die in 20s due to respiratory failures
  •   No cure, but myoblast therapy is promising
Developmental Aspects of Muscle
• Muscle tissue develops from embryonic
  mesoderm called myoblast
• Agrin – growth factor
• Skeletal Muscle – multinucleated due to the
  fusing of myoblasts
• Smooth and Cardiac – myoblasts do not fuse
  but do develop gap junctions
Regeneration
• Cardiac and Skeletal muscles become amitotic
  but retain ability to lengthen and thicken
• Satellite cells – cells that float around fixing
  damaged skeletal fibers
  • Limited regenerative ability
• Cardiac cells lack satellite cells
• Smooth muscle has good regenerative abilities
After Birth
• Muscular development reflects neuromuscular
 coordination

• Development occurs head-to-toe and proximal-
 to-distal

• Athletics and training can improve
 neuromuscular control
Male vs. Female
• Men                            • Women
  •Biological factors make         • Skeletal muscle make up
  men stronger than women          36% of body mass
     •Skeletal muscle makes up
     42% of body mass


  •Men have testosterone, sex
                                   •Body strength per unit
  hormone due to difference
  in men and women                 muscle mass is about the
                                   same in males as females
Aging
• With age, connective tissue increase and
    muscle fibers decrease
•   Muscles become stringier
•   By age 80, 50% of muscle mass is lost
    (sarcopenia)
•   Regular exercise reverses sarcopenia
•   Aging of cardiovascular system affects every
    organ in the body

				
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posted:8/15/2012
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