- In an accident with farm machinery, Mr. R. had his
left arm severed just below the elbow. Mrs. R.
stopped the bleeding, called for an ambulance,
and packed the severed arm in ice for the EMTs
to take to the hospital. Will Mr. R. ever be able
to move the fingers of his left hand again? What
structures must be reattached, and what has to
happen? - Name all of the muscles you can think of that move
the thigh at the hip. Group them as synergists, if
possible. Then pair those groups or individual
muscles as antagonists. - Muscle contraction is important for posture.
Muscles oppose each other, contracting equally to
keep us upright. Picture the body in anatomic posi-
tion, and describe what would happen if each of
these muscles relaxedcompletely:
Semispinalis capitis
Masseter
Rectus abdominis
Sacrospinalis
Quadriceps femoris
Gluteus maximus- An exercise for skiers involves sitting against a wall
as if you were sitting in a chair, but without a chair.
Thighs should be parallel to the floor and the knees
should make a 90oangle. Try it. What kind of
exercise is this? Which muscles are doing most of
the work (which ones begin to hurt)? Which do
you think would be easier: 3 minutes of this exer-
cise or 3 minutes of jogging? Can you think of an
explanation? - Can you juggle? Don’t just say “no”—have you
ever tried? Find some old tennis balls and try jug-
gling two balls with one hand, or three balls with
two hands. Explain how muscle sense is involved in
juggling.
Now try to imagine what it would be like to be
without muscle sense. Some people do not have
muscle sense in certain parts of their bodies. Who
are these people, and what has happened that cost
them their muscle sense (and muscle contraction)?
162 The Muscular System
FOR FURTHER THOUGHT
- In terms of ions and charges, describe: (p. 145)
a. Polarization
b. Depolarization
c. Repolarization - With respect to the sliding filament mechanism,
explain the function of: (p. 146)
a. Acetylcholine
b. Calcium ions
c. Myosin and actin
d. Troponin and tropomyosin
e. Cholinesterase- State three of the body’s physiological responses
to exercise, and explain how each helps maintain
homeostasis. (pp. 147–148) - Find the major muscles on yourself, and state a
function of each muscle