Muscular System
Mader
Study Questions 6-10
6. What is the all-or-none law? What is the
difference between a single muscle twitch,
summation and tetanus (p.114)
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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.
6. Continued: What is the difference
between a single muscle twitch, summation
and tetanus (p.114)
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Smt: 3 periods
1.
2.
3.
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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
Tetanus is an infectious disease caused by contamination of wounds
from bacteria that live in the soil.
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
8. What is the difference between isotonic
and isometric contraction? What is muscle
tone? How does muscle contraction affect
muscle size? (p. 115)
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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)
8. Continued: How does muscle
contraction affect muscle size?
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Hypertrophy – strenuous exercise over a
prolonged period causes muscles to get bigger
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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
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. How do muscles get their names? Give an
example for each method of naming a muscle? (p.
117)
1.
2.
3.
4.
5.
6.
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. Which of the head muscles are used for
facial expression? Which are used for
chewing? (p. 120)
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Orbicularis oculi - ~ eye = crows feet
Orbicularis orbis - ~ mouth = pucker
Buccinator – compresses cheek
(trumpeter’s muscle)
Zygomaticus – cheek bone attachment =
smiles
10. Continued: Which are used for
chewing = mastication
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Masseter – zygomatic arch to mandible &
raises mandible (prime mover)
Temporalis – fan-shaped muscle over the
temporal bone & acts as synergist to the
masseter