Muscular System

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Muscular System

• Mader
• Study Questions 6-10

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6. What is the all-or-none law? What is the
difference between a single muscle twitch,
summation and tetanus (p.114)

• An individual muscle fiber will contract
  completely or not at all, HOWEVER,
• The strength of a contraction of an entire muscle
  can increase according to how many fibers are
  contracted (not necessarily all of the fibers)
• THEREFORE, the entire muscle does not follow the
  all-or-none law.

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6. Continued What is the difference between a
single muscle twitch, summation and tetanus
(p.114)

• Smt 3 periods
• Latent time between stim. contraction
• Contraction
• Relaxation
• Summation many impulses in rapid successtion
• Tetanus when a muscle is not allowed to relax
  completely between stimuli

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Tetanus is an infectious disease caused by
contamination of wounds from bacteria that live
in the soil.
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7. Describe how muscles are attached to bone.
Define the terms prime mover, synergist and
antagonist. (p. 115)

• Origin on the stationary bone
• Insertion on the bone that moves
• Prime mover the one muscle that does most of
  the work when several muscles work together to
  move a bone
• Synergists muscles assisting the prime mover
  muscles can only pull not push
• Antagonists muscle pairs that work in
  opposition to bring about movement in opposite
  directions

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8. What is the difference between isotonic and
isometric contraction? What is muscle tone? How
does muscle contraction affect muscle size? (p.
115)

• Isotonic muscles contract, shorten and movement
  occurs
• Isometric muscles contract but dont shorten
  and no movement occurs
• Muscle tone applies to whole muscle refers to
  condition where some fibers are always contracted
  (posture neck, trunk, legs)

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8. Continued How does muscle contraction affect
muscle size?

• Hypertrophy strenuous exercise over a prolonged
  period causes muscles to get bigger
• Muscles are stronger and fatigue slowly
• Increases the number of myofibrils
• Atrophy decrease in muscle mass due to
  inactivity (astronauts)
• Causes muscle fibers to shorten and leave body
  parts contracted in contorted positions

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According to researchers, after just 5 to 11 days
in space, astronauts can lose up to 20 percent of
their muscle fibers - that is a lot of loss!
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9. How do muscles get their names? Give an
example for each method of naming a muscle? (p.
117)

1. Size gluteus maximus
2. Shape deltoid
3. Direction of fibers rectus (straight)
   abdominalis
4. Location frontalis overlies frontal bone
5. Number of attachments biceps, triceps
6. Action extensor digitorum extends fingers

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10. Which of the head muscles are used for
facial expression? Which are used for chewing?
(p. 120)

• Orbicularis oculi - eye crows feet
• Orbicularis orbis - mouth pucker
• Buccinator compresses cheek (trumpeters
  muscle)
• Zygomaticus cheek bone attachment smiles

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10. Continued Which are used for chewing
mastication

• Masseter zygomatic arch to mandible raises
  mandible (prime mover)
• Temporalis fan-shaped muscle over the temporal
  bone acts as synergist to the masseter