Muscle
283
SECTION A CLINICAL TERMS
I band
257
isometric contraction
266
isotonic contraction
267
junctional feet
262
latent period
269
lateral sac
262
lengthening contraction
267
light chains
259
load
266
M line
257
motor end plate
264
motor neuron
264
motor unit
264
muscle
256
muscle fatigue
273
muscle fi ber
256
myoblast
256
myofi bril
257
myoglobin
274
myosin
257
neuromuscular junction
264
optimal length (L
0
)
271
oxidative fi ber
274
oxygen debt
273
power stroke
260
recruitment
276
red muscle fi ber
274
relaxation
258
rigor mortis
261
ryanodine receptor
262
sarcomere
257
sarcoplasmic reticulum
261
satellite cell
256
skeletal muscle
255
sliding-fi lament
mechanism
258
slow fi ber
274
slow-oxidative fi ber
274
smooth muscle
255
striated muscle
255
summation
270
tendon
256
tension
266
tetanus
270
thick fi lament
257
thin fi
lament
257
titin
257
transverse tubule
(T-tubule)
262
tropomyosin
257
troponin
257
twitch
268
unfused tetanus
270
white muscle fi ber
274
Z line
257
atropine
266
botulism
266
curare
266
denervation atrophy
277
disuse atrophy
277
Duchenne muscular
dystrophy
280
hypocalcemic tetany
280
muscle cramp
280
muscular dystrophy
280
myasthenia gravis
280
neostygmine
280
plasmapheresis
280
poliomyelitis
280
succinylcholine
266
thymectomy
280
SECTION A REVIEW QUESTIONS
1. List the three types of muscle cells and their locations.
2. Diagram the arrangement of thick and thin fi laments in a
striated muscle sarcomere, and label the major bands that give
rise to the striated pattern.
3. Describe the organization of myosin, actin, tropomyosin, and
troponin molecules in the thick and thin fi laments.
4. Describe the four steps of one cross-bridge cycle.
5. Describe the physical state of a muscle fi ber in rigor mortis and
the conditions that produce this state.
6. What three events in skeletal muscle contraction and relaxation
depend on ATP?
7. What prevents cross-bridges from attaching to sites on the thin
fi laments in a resting skeletal muscle?
8. Describe the role and source of calcium ions in initiating
contraction in skeletal muscle.
9. Describe the location, structure, and function of the
sarcoplasmic reticulum in skeletal muscle fi
bers.
10. Describe the structure and function of the transverse tubules.
11. Describe the events that result in the relaxation of skeletal
muscle fi bers.
12. Defi ne a motor unit and describe its structure.
13. Describe the sequence of events by which an action potential
in a motor neuron produces an action potential in the plasma
membrane of a skeletal muscle fi
ber.
14. What is an end-plate potential, and what ions produce it?
15. Compare and contrast the transmission of electrical activity at
a neuromuscular junction with that at a synapse.
16. Describe isometric, concentric, and eccentric contractions.
17. What factors determine the duration of an isotonic twitch in
skeletal muscle? An isometric twitch?
18. What effect does increasing the frequency of action potentials
in a skeletal muscle fi ber have upon the force of contraction?
Explain the mechanism responsible for this effect.
19. Describe the length-tension relationship in skeletal muscle
fi bers.
20. Describe the effect of increasing the load on a skeletal muscle
fi ber on the velocity of shortening.
21. What is the function of creatine phosphate in skeletal muscle
contraction?
22. What fuel molecules are metabolized to produce ATP during
skeletal muscle activity?
23. List the factors responsible for skeletal muscle fatigue.
24. What component of skeletal muscle fi bers accounts for the
differences in the fi bers’ maximal shortening velocities?
25. Summarize the characteristics of the three types of skeletal
muscle fi bers.
26. Upon what three factors does the amount of tension developed
by a whole skeletal muscle depend?
27. Describe the process of motor-unit recruitment in controlling
(a) whole-muscle tension and (b) velocity of whole-muscle
shortening.
28. During increases in the force of skeletal muscle contraction,
what is the order of recruitment of the different types of motor
units?
29. What happens to skeletal muscle fi bers when the motor neuron
to the muscle is destroyed?
30. Describe the changes that occur in skeletal muscles following a
period of (a) long-duration, low-intensity exercise training; and
(b) short-duration, high-intensity exercise training.
31. How are skeletal muscles arranged around joints so that a limb
can push or pull?
32. What are the advantages and disadvantages of the muscle-
bone-joint lever system?
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