The Muscular System

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The Muscular System
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Muscle Control
Skeletal
Skeletal
Cardiac
Smooth
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Types of Responses

• Twitch-
• A single brief contraction
• Not a normal muscle function
• Tetanus
• One contraction immediately followed by another
• Muscle never completely returns to a relaxed
  state
• Effects are compounded

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Where Does the Energy Come From?

• Energy is stored in the muscles in the form of
  ATP
• ATP comes from the breakdown of glucose during
  Cellular Respiration
• This all happens in the Mitochondria of the cell
• When a muscle is fatigued (tired) it is unable to
  contract because of lack of Oxygen

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• Muscle Contraction
• The nerve impulse from motor neuron reaches
  synapse.
• The impulse triggers the release of acetylcholine
  in the synapse.     
• Acetylcholine binds to receptors on surface of
  muscle cell, triggers an impulse. 
• Calcium ions in sarcoplasmic reticulum move
  toward bind to troponin.
• Troponin moves out, allowing actin and myosin to
  react.
• The thin actin filaments slides inside the myosin
  filaments, shortening. This is repeated for each
  sarcomere, along the muscle fiber.  This causes a
  shortening of the entire muscle.

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Muscle Relaxation

1. An enzyme present in the synaptic cleft,
   acetylcholinesterase, destroys Ach shortly after
   it is bound to the receptors. The membrane, thus,
   no longer, responds to impulse. 
2. Ca goes off troponin and is transported by into
   its storage vesicles (using ATP). Actin and
   myosin are no longer linked.  
3. The sarcomere slides back into resting position.
   The muscle relaxes.

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Muscle Contractions

• Isotonic- muscles shorten/lengthen and movement
  occurs (most normal exercise)
• Isometric- muscle is activated, but it is held at
  a constant length

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Injuries to the Muscles

• Just like our skeletal system, sometimes we may
  injure our muscles.

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Types of Injuries

• Contusions (muscle bruises)
• One of most common experienced by athletes
• Often caused by direct trauma/repeated blow
• Muscle Strains
• Occurs when muscle is overstretched or pulled
• Can be caused by sudden/forceful contraction of
  muscle (lifting heavy weight)
• Tendonitis (inflammation of the tendon)
• Occurs when tendon is irritated and inflamed
• Can be caused by sudden pull on tendon and
  overuse/repetitive movements

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Muscle Strains

• Tears are often called pulled or strained
  muscles.
• The degree of the injury will determine treatment
  and recovery time.

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Categories of Muscle Strains

• Grade I Strain This is a mild strain and only
  some muscle fibers have been damaged. Healing
  occurs within two to three weeks.
• Grade II Strain This is a moderate strain with
  more extensive damage to muscle fibers, but the
  muscle is not completely ruptured. Healing occurs
  within three to six weeks.
• Grade III Strain This is a severe injury with a
  complete rupture of a muscle. This typically
  requires a surgical repair of the muscle the
  healing period can be up to three months.

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Body Building

• Many people work very hard to build their
  muscles.
• They use various exercises to build strength and
  muscle mass.
• This is a common practice with many men and women
  today, and many compete in contests.

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How much is too much?
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Flexion
Types of Musculo-Skeletal Movement
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Extension
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Hyperextension
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Abduction, Adduction Circumduction
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Rotation
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More Types of Movement

• Inversion- turn sole of foot medially
• Eversion- turn sole of foot laterally
• Pronation- palm facing down
• Supination- palm facing up
• Opposition- thumb touches tips of fingers on the
  same hand