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68
Muscle Physiology
A. Multiple Choice
Key/
Page
No.
336
a. striated.
b. unstriated.
c. voluntary.
d. Both striated and voluntary.
e. Both unstriated and involuntary.
336
volume.
a. 50%
b. 60%
c. 70%
d. 80%
e. 90%
338
a. A bands
b. H bands
c. I bands
d. sarcoplasmic reticulum
e. Z lines
339
a. participate in the propagation of an action potential along the surface of the
muscle fiber.
b. bind troponin, which in turn permits tropomyosin to uncover the cross-bridge
binding site on the thin filament.
c. bind tropomyosin, which in turn permits troponin to uncover the cross-bridge
binding site on the thin filament.
d. activate a calcium-calmodulin-dependent protein kinase, which in turn
phosphorylates and activates myosin.
69
341
contraction?
a. As the sarcomere shortens, the H zone becomes smaller.
b. As the sarcomere shortens, the width of the A band remains the same.
c. As the sarcomere shortens, the I band becomes smaller.
d. Two of these.
e. All of these.
343
a. activation of Ca2+ ATPase pumps which triggers a rise in intracellular calcium
levels
b. dihydropyridine to bind calcium channel receptors which triggers a rise in
intracellular calcium levels.
c. activation of stretch-activated Ca2+ channels which triggers a rise in intracellular
calcium levels.
d. activation of dihydroxypyridine receptors in membrane of the T tubule which
triggers a rise in intracellular calcium levels.
e. ryanodine to bind calcium channel receptors which triggers a rise in intracellular
calcium levels.
344 -
346
in the contraction cycle? The events numbered 1 through 6 may be used more than once.
1. Mysoin binds ATP
2. Mysoin hydrolyzes ATP and goes into cocked position
3. Myosin releases ADP and inorganic phosphate
4. Myosin binds actin filament
5. Power stroke
6. Myosin releases actin filament
a. 1, 2, 3, 4, 5, 6, 1
b. 1, 2, 4, 3, 5, 1, 6
c. 1, 6, 2, 4, 3, 5, 1, 6
d. 1, 2, 6, 3, 4, 5, 6, 1
e. None of these.
343 -
346
on a column, pour a mix of the muscle proteins through, wash first to get out the
nonspecific proteins and then do a second to wash to obtain myosin. Based on the
contraction cycle, your first wash should
a. include ATP, but the second wash should not.
b. not include ATP, but the second wash should.
c. include ATP, as should the second wash.
d. not include ATP, and neither should the second.
e. should include calcium, but the second one should not.
70
347,
348
a. Rigor mortis occurs as a result of a rise in intracellular calcium concentrations.
b. In skeletal muscle a single action potential lasts about 5-10 msec.
c. In skeletal muscle the relaxation time lasts slightly longer than the contractile
time.
d. In skeletal muscle the contractile response ceases when the lateral sacs take up
Ca2+.
e. A spring can move much faster than a muscle can contract.
350
a. a muscle and the motor neurons that innervate it.
b. a muscle fiber and the motor neurons that innervate it.
c. a motor neuron and the muscle fibers it innervates.
d. a motor neuron and the muscle it innervates.
e. none of these.
350
fiber?
a. the number of motor units recruited
b. the frequency of action potentials conducted by the motor neuron
c. the length of the fiber at the onset of contraction
d. diameter of the muscle fiber
e. All of these affect tension development by a muscle fiber.
353
a. a single muscle fiber may be innervated by multiple motor neurons.
b. a single motor neuron forms multiple synapses (multiterminal innervation) with
a single muscle fiber.
c. development of muscle tension is modulated by inhibitory presynaptic inputs.
d. muscle fibers are innervated by both excitatory and inhibitory neurons.
e. All of these.
71
354
than lo?
a. Not as much Ca2+ is released in a sarcomere with a length less than lo..
b. Interference between actin filaments originating from opposite ends of the
sarcomere prevents maximal or optimal cross-bridge formation.
c. The muscle fiber runs out of ATP.
d. In this situation, Ca2+ availability and the position of the actin filaments are
responsible for the decrease in muscle shortening because ATP will still be
available.
e. All of these contribute to reduced muscle shortening in a sarcomere with a length
less than lo.
355,
356
a. Muscle tension is produced internally within the sarcomeres.
b. Muscle tension is transmitted to the skeleton by tightening of the series-elastic
component within the sarcomere.
c. It is possible for a skeletal muscle to produce movement without the muscle being
attached to bone at both ends.
d. With respect to skeletal muscle, the load and velocity for shortening are inversely
related for concentric contractions.
e. Actually, all of these are true statements.
72
355
a. tension (or force) increases, but length stays the same.
b. tension (or force) stays the same, but length increases.
c. tension (or force) stays the same, and length stays the same.
d. tension (or force) stays the same, but length decreases.
e. tension (or force) decreases, and length decreases.
355
a. circular muscles (like those in the iris of the eye) contract, making a smaller
aperture.
b. muscle length shortens while tension remains constant.
c. muscle lengths shorten, drawing objects closer to the body midline.
d. None of these.
359
accomplished with a non-hydrolyzable form of ATP such as ATP--S for example?
a. cocking of the cross-bridge in anticipation of the power-stroke
b. release of actin by myosin
c. sequestration of calcium into the sarcoplasmic reticulum
d. All of these could be accomplished with ATP--S.
e. None of these could be accomplished with ATP--S.
359
ADP to ATP during muscle activity.
a. Glucose-1-phosphate
b. Glucose-6-phosphate
c. NADPH
d. Creatine-phosphate
e. NADH
359
of its role in muscle energetics, which of the following statements is true?
a. The concentration of creatine rises as the concentration of ATP rises.
b. The concentration of creatine falls as the concentration of ATP rises.
c. The concentration of creatine is independent of the concentration of ATP.
d. The concentration of creatine rises as the concentration of ADP rises.
359
a. to transport oxygen in the blood
b. to hold together the lipid bilayers that collectively form a myelin sheath
c. to increase the rate of transfer of oxygen from the blood to the muscle
d. to mark foreign bodies for consumption by macrophages
e. None of these.
73
361
a. pyruvic acid.
b. lactic acid.
c. ethanol.
d. acetyl CoA.
e. carbon dioxide.
362
contraction by skeletal muscle?
a. 15%
b. 25%
c. 50%
d. 60%
e. 75%
362
a. are able to take up oxygen more quickly from the blood.
b. are equipped with a myosin-ATPase with more rapid kinetics.
c. are able to generate ATP more rapidly.
d. conduction action potentials more rapidly.
e. are recruited by the nervous system more rapidly.
363
a. it's correlated with its large volume, which in turn means it can hold more
oxygen, and generate ATP aerobically.
b. it implies more cross-sectional area and the fiber can therefore hold more
mitochondria, which means it can generate more ATP to power contraction.
c. it has less surface area relative to its volume, so it depolarizes more rapidly, since
current has less distance to spread.
d. it has more myofibrils per unit length, which means it can form more
cross-bridges, and generate more power (force).
e. none of these.
363
a. slow oxidative fibers (Type I)
b. fast oxidative fibers (Type IIa)
c. fast glycolytic fibers (Type IIx)
d. fast and slow glycolytic fibers
e. fast and slow oxidative fibers
368
a. sensory afferents and/or internurons.
b. cortical neurons whose cell bodies reside in the primary motor cortex.
c. cortical neurons whose cell bodies reside in the somatosensory cortex.
d. cerebellar neurons.
e. brain stem neurons.
74
370
about muscle length, whereas the ________ gives information about muscle tension.
a. muscle spindle; Golgi tendon organ
b. Golgi tendon organ; muscle spindle
c. muscle spindle; Golgi apparatus
d. Golgi apparatus; muscle spindle
e. None of these.
370
a. regulated by the activity of motor neurons.
b. activated by sensory input from the muscle spindle.
c. activated by changes in muscle tension.
d. activated by changes in muscle length.
e. activated by input from the muscle receptor organ.
370,
371
a. Gamma motor neuron activity is too weak to affect whole muscle tension.
b. Golgi tendon organs lie within the belly of the muscle.
c. A muscle spindle is a collection of extrafusal fibers.
d. The primary purpose of the stretch reflex is to counteract the unintended
contraction of the quadriceps.
e. Each muscle spindle has one efferent and two afferent neurons which are used for
reciprocal innvervation.
373 –
375
common?
a. Calcium is bound by the protein calmodulin prior to formation of cross-bridges.
b. Tropomyosin is removed from the myosin-binding site on actin, permitting
formation of cross-bridges
c. Sliding of thick and thin filaments relative to one another depends on a rise in
cytosolic calcium.
d. Sliding of thick and thin filaments relative to one another results in shortening of
the sarcomeres.
e. All of these.
375
a. tropomyosin.
b. caldesmon
c. myosin light chain kinase
d. calmodulin
e. synapsin
75
378
a. contraction occurs following a spontaneous depolarization event.
b. contraction is regulated by pacemaker cells lying within the muscle.
c. the muscle is stimulated to contract through direct nervous input.
d. contraction is proportional to the generator potential of the nerve.
e. more than one of these.
381
increases in the volume of its contents. Typically, an upper limit is placed on the volume,
however, by
a. reflex contraction initiated in response to stretch.
b. tension due to stretching of the intermediate filaments within the smooth muscle.
c. inelastic connective tissue associated with the smooth muscle of the organ.
d. the number of cross-bridge sites present on the myosin filaments.
374,
375
a. Cardiac muscle contraction is modified by hormones.
b. Cardiac cells lack T tubules.
c. Only cardiac muscle has slow myosin ATPase activity.
d. In skeletal muscle Ca2+ is released from the sarcoplasmic reticulum.
e. Skeletal muscle has thick myosin and thin actin filaments
375,
376
a. Smooth muscle can be classified according to the timing and means of increasing
cytosolic Ca2+.
b. In smooth muscle, C-type Ca2+ channels regulate the influx of extracellular Ca2+.
c. Smooth muscle tone exists because the muscle has a relatively low resting
potential.
d. In smooth muscle, Ca2+ binds directly to myosin light chain kinase as opposed to
troponin as it does in skeletal muscle.
e. Skeletal, cardiac, and smooth muscle differ in the energy source used for
contraction.
374,
375
a. Only smooth muscle contraction is modified by hormones.
b. Only smooth muscle takes up Ca2+ from the extracellular fluid.
c. Only skeletal muscle is neurogenic.
d. Only skeletal muscle has a moderately developed sacroplasmic reticulum.
e. Two of these.
380
a. are bulges at the end of certain types of nerve terminal branches
b. can be found on the postganglionic autonomic fibers associated with certain
smooth muscle cells
c. contain neurotransmitter
d. all of these
e. none of these.
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379
a. increasing the number of individual cells recruited by neurons to contract.
b. increasing the levels of cytoplasmic calcium available to permit cross-bridge
formation.
c. increasing the synthesis of contractile units so that more power is attained.
d. doing all of these.
e. doing none of these.
375
a. skeletal
b. multiunit smooth muscle
c. single-unit smooth muscle
d. cardiac muscle
e. all of these
375
a. skeletal
b. smooth
c. cardiac
d. both skeletal and cardiac
e. both smooth and cardiac
B. True of False
338
339
342 contraction.
347
381 action potential that produced it.
350
352 strength.
354 their optimal length which maximizes contraction strength.
77
356
365 usage, fast-glycolytic fibers can be converted to slow-glycolytic fibers.
C. Matching (correct answers are aligned with each number; e.g., #1 matches with letter a)
D. Essay
Page No.
muscle.
present in skeletal muscle cells?.
phosphate come from?
cells and myogenic single-unit smooth muscle cells.
