Muscle Physiology

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Muscle Physiology

• Anatomy Physiology/Tissues, Bones and Muscles

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Muscle Functions

• Muscles have four major roles in our bodies
• Produce movement
• Maintain posture
• Stabilize joints
• Generate heat a by-product of
• muscle activity

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Anatomy of a Muscle

• To understand how muscles move, it is essential
  to understand their basic anatomy.
• The outermost layer of a muscle is called the
  epimysium, which is a very tough connective tissue

Epimysium
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Muscle Anatomy Continued

• Below the epimysium is another layer of
  connective tissue called the perimysium, which
  covers bundles of muscle cells called a fascicle.

Fascicle
Perimysium
Epimysium
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Anatomy of a Muscle Continued

• Each muscle fiber in the fascicle is wrapped by a
  thin connective tissue called an endomysium.

Endomysium
Fascicle
Perimysium
Epimysium
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Muscle Fibers

• Successful muscle movement (contraction or
  relaxation of a muscle) depends on a very
  organized coordination of many parts of the
  muscle.
• A single muscle cell is often called a muscle
  fiber, because it is long and contains multiple
  nuclei.

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Myofibrils

• A single muscle fiber is made of many myofibril
  organelles.

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Actin and Myosin Filaments

• Each myofibril is made of a combination of actin
  filaments, which are thin, and myosin filaments,
  which are thick.
• The actin and myosin are arranged in repeating
  units called sarcomeres.

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Parts of the Sarcomere

• Each area of the sarcomere has a specific name,
  because these units are essential for
  understanding how muscles contract and relax
• Thin (actin) filaments are attached to membranes
  called Z discs (or Z lines). A full sarcomere
  extends from one Z disc to another.
• A bands contain both thin (actin) and thick
  (myosin) filaments.
• I bands contain only thin (actin) filaments and
  span parts of two sarcomeres.
• Alternating light (I) and dark (A) bands give the
  myofibril a striped appearance.
• The H zone contains only thick (myosin)
  filaments.

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Muscle Movement

• When muscles contract (shorten) the Z discs move
  closer together. This means that the H zone
  becomes smaller and the the I bands shorten.
• When muscle relax (lengthen), the Z discs move
  apart. The means that the H zone becomes larger
  and the I bands get longer.

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Muscle Movement Continued

• The movement of sarcomeres is controlled by
  crossbands that connect actin and myosin.
• These crossbands attach the myosin and actin
  filaments and use ATP as a source of energy to
  slide the filaments across each other.
• This model of muscle movement is known as the
  Sliding Filament Theory.
• http//highered.mcgraw-hill.com/sites/0072437316/s
  tudent_view0/chapter42/animations.html

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Prentice Hall Muscle Contraction Video

• 4 minutes
• http//www.youtube.com/watch?v83yNoEJyP6g