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Muscular System

This study guide answers questions about the all-or-none law, single muscle twitch, summation, tetanus, muscle attachment, and the effects of muscle contraction on muscle size. It also discusses how muscles get their names and the head muscles used for facial expression and chewing.

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Muscular System

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  1. Muscular System Mader Study Questions 6-10

  2. 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.

  3. 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

  4. Tetanus is an infectious disease caused by contamination of wounds from bacteria that live in the soil.

  5. 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

  6. 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 don’t shorten and no movement occurs • Muscle tone – applies to whole muscle refers to condition where some fibers are always contracted (posture – neck, trunk, legs)

  7. 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

  8. 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!

  9. 9. How do muscles get their names? Give an example for each method of naming a muscle? (p. 117) • Size – gluteus maximus • Shape – deltoid • Direction of fibers – rectus (straight) abdominalis • Location – frontalis overlies frontal bone • Number of attachments – biceps, triceps • Action – extensor digitorum extends fingers

  10. 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 (trumpeter’s muscle) • Zygomaticus – cheek bone attachment = smiles

  11. 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

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