Muscle Anatomy

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Muscle Anatomy

• Anatomy and Physiology L3

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Lets Review!!What type of muscle tissue does
each describe?

• Long, thin multinucleated
• Striated
• Involuntary
• Contracts rhythmically
• Found in cardiac tissue

• Voluntary
• Contractions are slow and steady
• Walls of visceral organs blood vessels
• Contract rapidly vigorously

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Functions

• Movement
• Skeletal
• Cardiac
• Smooth
• Posture Maintenance (skeletal)
• Joint stability (skeletal)
• Heat generation (skeletal)

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Gross Anatomy of Muscle
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Gross Anatomy

• Fascia outer, toughest covering of Dense CT
• Epimysium Each skeletal second fibrous layer
• Each made up of many bundles of fascicles

• Perimysium another CT, wrapping each fascicle
• Fascicle group of bundled muscle fibers
• Endomysium thin, delicate inner layer wrapping
  each muscle fiber (cell)

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Myofibril (make-up of fiber)

• Bundles of muscle fibers
• Sarcolemma cell membrane
• SR similar to ER
• Sarcomere contractile unit
• Multi-nucleate

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Microscopic view

• What are these stripes?
• Circles?

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Myofibril

• Thread-like protein structures
• 2 types
• Thick Myosin
• Thin Actin
• Alternating light/dark create striations
• Allow muscle to contract (shorten) and relax
  (lengthen)

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Skeletal Muscle fiber
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Take a Break and Review!

• Go to following animation
• www.brookscole.com/chemistry_d/templates/student_r
  esources/shared_resources/animations/muscles/muscl
  es.html
• Great animations and review activities!

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Sarcoplasmic Reticulum (SR)

• Primary Fxn storage of calcium
• High concentration of Calcium (Ca)
• Maintained by Calcium pump

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Homework! (please type)

• Protein structure of muscle mainly made up of
  Actin Myosin. Describe 2 others.
• What is the function of dystrophin?
• What is Muscular Dystrophy?
• Cause
• Physiological effects
• Clinical affects
• Difference between Duchanne MD and Becker MD?

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Motor Unit Composed of motor neuron all the
muscle fibers

• NM Jxn
• Terminal end stores ACh
• ACh released into fiber
• ACh acts as stimulus

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Steps in Muscle Contraction
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Steps in Muscle Contraction

• Nerve impulse travels down motor neuron to NM
  junction
• Acetylcholine (ACh) released into muscle
• ACh diffuses across muscle fiber
• Signals the SR to release Calcium stores
• Ca initiates formation of crossbridges between
  Actin and Myosin (ATP)
• Ca stimulates a change in Myosin shape

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Steps in Muscle Relaxation

• Motor neuron impulse to stop contraction
• Ca moves (Active transport) back into SR (to be
  stored) (ATP)
• Absence of Ca causes crossbridges to break
  because Myosin changes back its shape
• Actin filaments slide back (ATP)
• RESULT Muscle relaxes