Question 1

Slow oxidative fibers in skeletal muscle have

Accepted Answer

A)  few mitochondria but abundant sarcoplasmic reticulum. 
B)  few mitochondria but numerous capillaries. 
C)  large diameters, to hold many mitochondria. 
D)  low levels of glycolytic enzymes but high levels of oxidative enzymes. 
A)  few mitochondria but abundant sarcoplasmic reticulum. 
B)  few mitochondria but numerous capillaries. 
C)  large diameters, to hold many mitochondria. 
D)  low levels of glycolytic enzymes but high levels of oxidative enzymes.

Question 2

In skeletal muscle, an incomplete tetanus would result from

Accepted Answer

A)  action potentials arriving at a rate fast enough for the intracellular Ca2+ levels to rise much higher than they would in a muscle twitch. 
B)  action potentials arriving at a rate fast enough for sarcomeres to generate force while the elastic components of the muscle are still stretched. 
C)  action potentials arriving so quickly that there is no fluctuation in intracellular Ca2+ levels. 
D)  many, but not all, of the thin filaments being activated to permit cross-bridge formation. 
A)  action potentials arriving at a rate fast enough for the intracellular Ca2+ levels to rise much higher than they would in a muscle twitch. 
B)  action potentials arriving at a rate fast enough for sarcomeres to generate force while the elastic components of the muscle are still stretched. 
C)  action potentials arriving so quickly that there is no fluctuation in intracellular Ca2+ levels. 
D)  many, but not all, of the thin filaments being activated to permit cross-bridge formation.

Question 3

In relaxed skeletal muscle, myosin heads are

Accepted Answer

A)  bound to actin with ADP and phosphate bound. 
B)  bound to actin with ATP bound. 
C)  dissociated from actin with ATP bound. 
D)  dissociated from actin with ADP and phosphate bound. 
A)  bound to actin with ADP and phosphate bound. 
B)  bound to actin with ATP bound. 
C)  dissociated from actin with ATP bound. 
D)  dissociated from actin with ADP and phosphate bound.

Question 4

Which type of muscle does not use troponin as part of the excitation-contraction coupling mechanism?

Accepted Answer

A)  Skeletal muscle 
B)  Smooth and cardiac muscle 
C)  Smooth muscle 
D)  All muscles use troponin. 
A)  Skeletal muscle 
B)  Smooth and cardiac muscle 
C)  Smooth muscle 
D)  All muscles use troponin.

Question 5

Lengthening of a muscle occurs

Accepted Answer

A)  as a result of an external load that acts on the muscle. 
B)  as the muscle cell action potential repolarizes. 
C)  as Ca2+ levels drop following a contraction. 
D)  only when the muscle is generating negative force. 
A)  as a result of an external load that acts on the muscle. 
B)  as the muscle cell action potential repolarizes. 
C)  as Ca2+ levels drop following a contraction. 
D)  only when the muscle is generating negative force.

Question 6

The extraocular muscles that move the mammalian eyeball can contract and relax at much higher frequencies than the muscles of the limbs, but they produce relatively low force as they rotate the eye. These characteristics tell us that extraocular muscles have

Accepted Answer

A)  high levels of myosin. 
B)  a high volume fraction of myofibrils. 
C)  a high volume fraction of sarcoplasmic reticulum. 
D)  troponin C with high Ca2+ affinity. 
A)  high levels of myosin. 
B)  a high volume fraction of myofibrils. 
C)  a high volume fraction of sarcoplasmic reticulum. 
D)  troponin C with high Ca2+ affinity.

Question 7

For muscle, the work produced during any given contractile event is equal to

Accepted Answer

A)  force multiplied by distance. 
B)  speed multiplied by the distance. 
C)  force of the contraction multiplied by the distance the load is displaced. 
D)  speed of the contraction multiplied by the distance the load is displaced. 
A)  force multiplied by distance. 
B)  speed multiplied by the distance. 
C)  force of the contraction multiplied by the distance the load is displaced. 
D)  speed of the contraction multiplied by the distance the load is displaced.

Question 8

Lactate produced by muscle cells

Accepted Answer

A)  is produced only during very intense exercise. 
B)  is always broken down to yield ATP within the muscle cell that produced it. 
C)  is always used to produce glucose by gluconeogenesis in the cell that produced it. 
D)  can be exported into the bloodstream and used by other cells. 
A)  is produced only during very intense exercise. 
B)  is always broken down to yield ATP within the muscle cell that produced it. 
C)  is always used to produce glucose by gluconeogenesis in the cell that produced it. 
D)  can be exported into the bloodstream and used by other cells.

Question 9

ATP use is lower in smooth muscle than in skeletal muscle in part because

Accepted Answer

A)  there is no sarcoplasmic reticulum calcium ATPase in smooth muscle. 
B)  smooth muscle myosin does not require an ATP molecule for each cross-bridge cycle. 
C)  smooth muscle myosin completes the cross-bridge cycle more slowly than skeletal muscle myosin does. 
D)  calcium removal from the cytoplasm does not require ATP in smooth muscle. 
A)  there is no sarcoplasmic reticulum calcium ATPase in smooth muscle. 
B)  smooth muscle myosin does not require an ATP molecule for each cross-bridge cycle. 
C)  smooth muscle myosin completes the cross-bridge cycle more slowly than skeletal muscle myosin does. 
D)  calcium removal from the cytoplasm does not require ATP in smooth muscle.

Question 10

Which muscle can generate the most power per cubic centimeter of muscle?

Accepted Answer

A)  A muscle containing mostly slow oxidative fibers contracting at its Vmax 
B)  A muscle containing mostly slow oxidative fibers contracting against a moderate load 
C)  A muscle containing mostly fast glycolytic fibers contracting at its Vmax 
D)  A muscle containing mostly fast glycolytic fibers contracting against a moderate load 
A)  A muscle containing mostly slow oxidative fibers contracting at its Vmax 
B)  A muscle containing mostly slow oxidative fibers contracting against a moderate load 
C)  A muscle containing mostly fast glycolytic fibers contracting at its Vmax 
D)  A muscle containing mostly fast glycolytic fibers contracting against a moderate load

Question 11

The smallest unit of a skeletal muscle that shortens during a muscle contraction is the

Accepted Answer

A)  myosin molecule. 
B)  thin filament. 
C)  sarcomere. 
D)  myofibril. 
A)  myosin molecule. 
B)  thin filament. 
C)  sarcomere. 
D)  myofibril.

Question 12

A skeletal muscle fiber with high myosin ATPase activity, a high rate of Ca2+ reuptake by the sarcoplasmic reticulum, and large number of mitochondria would be classified as a

Accepted Answer

A)  slow oxidative fiber. 
B)  fast oxidative glycolytic fiber. 
C)  fast glycolytic fiber. 
D)  slow glycolytic fiber. 
A)  slow oxidative fiber. 
B)  fast oxidative glycolytic fiber. 
C)  fast glycolytic fiber. 
D)  slow glycolytic fiber.

Question 13

Single-unit smooth muscle differs from multiunit smooth muscle in that multiunit smooth muscle

Accepted Answer

A)  contains gap junctions that link the cells as an electrical syncytium. 
B)  is often spontaneously active. 
C)  is usually stretch-activated. 
D)  has cells that function as independent units. 
A)  contains gap junctions that link the cells as an electrical syncytium. 
B)  is often spontaneously active. 
C)  is usually stretch-activated. 
D)  has cells that function as independent units.

Question 14

Suppose that each cross-bridge cycle moves the thin filament 10 nanometers relative to the thick filament. If myosin in a particular muscle can go through the cross-bridge cycle at 250 cycles per second, what is the rate at which a muscle that is 30 cm long can shorten?

Accepted Answer

A)  75 mm/s 
B)  0.30 m/s 
C)  0.60 m/s 
D)  2.5 m/s 
A)  75 mm/s 
B)  0.30 m/s 
C)  0.60 m/s 
D)  2.5 m/s

Question 15

Refer to the figure shown.
  In the figure, which panel represents the transient rigor state?

Accepted Answer

A)  I 
B)  IV 
C)  V 
D)  VI 
A)  I 
B)  IV 
C)  V 
D)  VI

Question 16

Which statement provides the most likely explanation for the differing patterns of innervation in arthropod skeletal muscle (polyneuronal) and vertebrate skeletal muscle (single innervation)?

Accepted Answer

A)  Vertebrates need to modulate muscle force, whereas arthropods always exert the same force with a given muscle. 
B)  Action potentials in vertebrate neurons are all-or-nothing, whereas arthropod neurons fire action potentials of varying magnitude. 
C)  Action potentials in arthropod neurons are all-or-nothing, whereas vertebrate neurons fire action potentials of varying magnitude. 
D)  The two patterns are products of the evolutionary history of the two taxa, and each one allows effective control of muscle contraction. 
A)  Vertebrates need to modulate muscle force, whereas arthropods always exert the same force with a given muscle. 
B)  Action potentials in vertebrate neurons are all-or-nothing, whereas arthropod neurons fire action potentials of varying magnitude. 
C)  Action potentials in arthropod neurons are all-or-nothing, whereas vertebrate neurons fire action potentials of varying magnitude. 
D)  The two patterns are products of the evolutionary history of the two taxa, and each one allows effective control of muscle contraction.

Question 17

Explain why a muscle always works by shortening and cannot actively increase its length unless an external force pulls on it.

Accepted Answer

During the cross-bridge cycle, myosin go

Question 18

Running mice are capable of moving their legs back and forth much more quickly than elephants. Thus, compared to an elephant muscle cell, a mouse muscle cell likely contains more

Accepted Answer

A)  actin. 
B)  myosin. 
C)  troponin C. 
D)  SR Ca2+-ATPase. 
A)  actin. 
B)  myosin. 
C)  troponin C. 
D)  SR Ca2+-ATPase.

Question 19

Which of the following is not a function of ATP in skeletal muscle?

Accepted Answer

A)  Releases calcium from the sarcoplasmic reticulum 
B)  Detachment of myosin from actin 
C)  Generates power strokes 
D)  Powers calcium pumps 
A)  Releases calcium from the sarcoplasmic reticulum 
B)  Detachment of myosin from actin 
C)  Generates power strokes 
D)  Powers calcium pumps

Question 20

Some crabs have giant skeletal muscle fibers that are much larger in diameter than muscle fibers found in most other animals. What fiber type are these fibers likely to be and why?

Accepted Answer

The giant fibers are fast glycolytic fib

Exam 20: Muscle

Slow oxidative fibers in skeletal muscle have

In skeletal muscle, an incomplete tetanus would result from

In relaxed skeletal muscle, myosin heads are

Which type of muscle does not use troponin as part of the excitation-contraction coupling mechanism?

Lengthening of a muscle occurs

The extraocular muscles that move the mammalian eyeball can contract and relax at much higher frequencies than the muscles of the limbs, but they produce relatively low force as they rotate the eye. These characteristics tell us that extraocular muscles have

For muscle, the work produced during any given contractile event is equal to

Lactate produced by muscle cells

ATP use is lower in smooth muscle than in skeletal muscle in part because

Which muscle can generate the most power per cubic centimeter of muscle?

The smallest unit of a skeletal muscle that shortens during a muscle contraction is the

A skeletal muscle fiber with high myosin ATPase activity, a high rate of Ca2+ reuptake by the sarcoplasmic reticulum, and large number of mitochondria would be classified as a

Single-unit smooth muscle differs from multiunit smooth muscle in that multiunit smooth muscle

Suppose that each cross-bridge cycle moves the thin filament 10 nanometers relative to the thick filament. If myosin in a particular muscle can go through the cross-bridge cycle at 250 cycles per second, what is the rate at which a muscle that is 30 cm long can shorten?

Refer to the figure shown. In the figure, which panel represents the transient rigor state?

Which statement provides the most likely explanation for the differing patterns of innervation in arthropod skeletal muscle (polyneuronal) and vertebrate skeletal muscle (single innervation)?

Explain why a muscle always works by shortening and cannot actively increase its length unless an external force pulls on it.

Running mice are capable of moving their legs back and forth much more quickly than elephants. Thus, compared to an elephant muscle cell, a mouse muscle cell likely contains more

Which of the following is not a function of ATP in skeletal muscle?

Some crabs have giant skeletal muscle fibers that are much larger in diameter than muscle fibers found in most other animals. What fiber type are these fibers likely to be and why?

Animals and Environments: Function on the Ecological Stage

Molecules and Cells in Animal Physiology

Genomics, Proteomics, and Related Approaches to Physiology

Physiological Development and Epigenetics

Transport of Solutes and Water

Nutrition, Feeding, and Digestion

Energy Metabolism

Aerobic and Anaerobic Forms of Metabolism

The Energetics of Aerobic Activity

Thermal Relations

Food, Energy, and Temperature at Work: The Lives of Mammals in Frigid Places

Neurons

Synapses

Sensory Processes

Nervous System Organization and Biological Clocks

Endocrine and Neuroendocrine Physiology

Reproduction

Integrating Systems at Work: Animal Navigation

Control of Movement

Movement and Muscle at Work: Plasticity in Response to Use and Disuse

Introduction to Oxygen and Carbon Dioxide in Physiology

External Respiration: the Physiology of Breathing

Transport of Oxygen and Carbon Dioxide in Body Fluids With an Introduction to Acid- Base Physiology

Circulation

Oxygen, Carbon Dioxide, and Internal Transport at Work: Diving by Marine Mammals

Water and Salt Physiology: Introduction and Mechanisms

Kidneys and Excretion With Notes on Nitrogen Excretion

Water, Salts, and Excretion at Work: Mammals of Deserts and Dry Savannas

Water and Salt Physiology of Animals in Their Environments

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A skeletal muscle fiber with high myosin ATPase activity, a high rate of Ca²⁺ reuptake by the sarcoplasmic reticulum, and large number of mitochondria would be classified as a