Relative to skeletal muscle, smooth muscle

Relative to skeletal muscle, smooth muscle

A) only uses less energy to generate a given amount of force.
B) only can sustain contractile force without fatigue.
C) only uses calcium from the sarcoplasmic reticulum and extracellular space.
D) uses less energy to generate a given amount of force and can sustain contractile force without fatigue.
E) uses less energy to generate a given amount of force, can sustain contractile force without fatigue and uses calcium from the sarcoplasmic reticulum and extracellular space.


Answer: : E

An important difference between single-unit and multiunit smooth muscle is the

An important difference between single-unit and multiunit smooth muscle is the

A) numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet.
B) longer actin and myosin filaments in multiunit smooth muscle, which allow coordination of contraction.
C) ability of single-unit fibers to change into multiunit fibers when advantageous.
D) closely controlled individual fibers in single-unit smooth muscle to allow fine control and graded contractions by selective activation.



Answer: : A

Put these myofibers in the order they would be recruited as the body moves from a weak to a strong stimulus:

Put these myofibers in the order they would be recruited as the body moves from a weak to a strong stimulus:

1. glycolytic fast-twitch fibers
2. fatigue-resistant oxidative fast-twitch fibers
3. fatigue-resistant slow-twitch fibers



A) 1, 2, 3
B) 2, 3, 1
C) 3, 2, 1
D) 1, 3, 2
E) 3, 1, 2


Answer: : C

The force generated by a single muscle fiber can be increased by

The force generated by a single muscle fiber can be increased by

A) increasing frequency of action potentials only.
B) increasing muscle length beyond optimal only.
C) increasing the asynchrony of recruitment only.
D) increasing frequency of action potentials and increasing muscle length beyond optimal only.


Answer: : A

Skeletal muscle fibers with the greatest endurance rely on ________ for energy.

Skeletal muscle fibers with the greatest endurance rely on ________ for energy.

A) anaerobic glycolysis
B) oxidative phosphorylation
C) lactic acid accumulation
D) ketone body degradation


Answer: : B

The factor(s) that determine the duration of a twitch in various types of fibers is the speed of the

The factor(s) that determine the duration of a twitch in various types of fibers is the speed of the

A) removal of Ca2+ ions from the sarcoplasm only.
B) hydrolysis of ATP only.
C) movement of Na+ across their membranes only.
D) removal of Ca2+ ions from the sarcoplasm and hydrolysis of ATP.
E) removal of Ca2+ ions from the sarcoplasm and hydrolysis of ATP and movement of Na+ across their membranes.


Answer: : A

After death, when metabolism stops, in which step of the contractile cycle must skeletal muscles remain?

After death, when metabolism stops, in which step of the contractile cycle must skeletal muscles remain?

A) It depends on what part of the contractile cycle they were in at the time of death.
B) the power stoke phase
C) the rigor state
D) a weak binding state


Answer: : C

Put these events in the correct chronological sequence:

Put these events in the correct chronological sequence:

1. End-plate potentials trigger action potentials.
2. Transverse tubules convey potentials into the interior of the cell.
3. Acetylcholine binds to receptors on the motor end plate.
4. Ca2+ is released from the sarcoplasmic reticulum.


A) 1, 2, 3, 4
B) 3, 1, 2, 4
C) 2, 1, 4, 3
D) 3, 1, 4, 2
E) 4, 3, 2, 1


Answer: : B

Which of the following is NOT a correct comparison of cardiac myocytes to other muscle cell types?

Which of the following is NOT a correct comparison of cardiac myocytes to other muscle cell types? 

A) Like smooth muscle cells, some cardiac myocytes have pacemaker potentials.
B) Like some smooth muscle cells, cardiac myocytes are electrically coupled.
C) Like skeletal muscle cells, actin and myosin are organized into sarcomeres.
D) Like skeletal muscle, contraction of cardiac muscle is under autonomic nervous control.
E) Like smooth muscle cells, cardiac muscle is under hormonal control.


Answer: : D

A change in smooth muscle cell tension in the absence of a change in electrical potential of the cells is described as a

A change in smooth muscle cell tension in the absence of a change in electrical potential of the cells is described as a

A) pacemaker potential.
B) slow wave potential.
C) pharmacomechanical coupling.
D) electromechanical coupling.


Answer: : C

The calcium release channel in the smooth muscle sarcoplasmic reticulum that is opened by increases in phospholipase C activity is the

The calcium release channel in the smooth muscle sarcoplasmic reticulum that is opened by increases in phospholipase C activity is the

A) inositol trisphosphate (IP3) receptor channel.
B) ryanodine receptor.
C) dihydropyridine (DHP) receptor.
D) voltage-gated Ca2+ channel.
E) Ca2+-ATPase.


Answer: : A

This protein is activated by the Ca2+-calmodulin complex to phosphorylate the myosin light chain protein.

This protein is activated by the Ca2+-calmodulin complex to phosphorylate the myosin light chain protein.

A) tropomyosin
B) myosin heavy chain
C) myosin light chain kinase
D) myosin light chain phosphatase


Answer: : C

Which of the following is NOT a property of single-unit smooth muscles?

Which of the following is NOT a property of single-unit smooth muscles? 

A) All smooth muscle cells are connected by gap junctions.
B) Their contraction occurs in a coordinated manner.
C) Electrical responses travel directly between cells.
D) Only a proportion of the smooth muscle cells receive autonomic nervous input.
E) Each cell functions independent of its neighbor.


Answer: : E

Smooth muscle cells lack which protein(s)?

Smooth muscle cells lack which protein(s)?

A) actin only
B) myosin only
C) troponin only
D) tropomyosin only
E) troponin and tropomyosin


Answer: : C

Compared to skeletal muscle, contraction of smooth muscle cells is

Compared to skeletal muscle, contraction of smooth muscle cells is

A) only a slower response to a stimulus.
B) only sustained without fatigue.
C) only controlled by the somatic nervous system.
D) a slower response to a stimulus and sustained without fatigue.
E) a slower response to a stimulus, sustained without fatigue, and controlled by the somatic nervous system.


Answer: : D

In order for the bicep muscle to shorten, the force applied by the muscle must be ________ the load applied at the hand.

In order for the bicep muscle to shorten, the force applied by the muscle must be ________ the load applied at the hand.

A) greater than
B) less than
C) equal to


Answer: : A

In the lever system that characterizes the interaction between bones and muscle, the bones act as the ________ whereas the joints form the ________.

In the lever system that characterizes the interaction between bones and muscle, the bones act as the ________ whereas the joints form the ________.

A) lever, fulcrums
B) fulcrum, levers
C) lever, pulleys
D) fulcrum, pulleys


Answer: : A

Before the entire muscle can change length, the force generated by the muscle must stretch the

Before the entire muscle can change length, the force generated by the muscle must stretch the 

A) eccentric contractile elements.
B) parallel elastic elements.
C) series elastic elements.
D) contractile elements.


Answer: : C

A contraction that generates enough force to move a load is known as ________, whereas one that generates force that equals the load is known as ________.

A contraction that generates enough force to move a load is known as ________, whereas one that generates force that equals the load is known as ________.

A) isotropic, isometric
B) isometric, eccentric
C) isotonic, isometric
D) isometric, isotonic
E) isotonic, eccentric


Answer: : C

The nervous system avoids muscle fatigue during submaximal contraction by

The nervous system avoids muscle fatigue during submaximal contraction by 

A) always recruiting slow-twitch motor units.
B) asynchronous recruitment.
C) synchronous recruitment.
D) always recruiting fast-twitch motor units.


Answer: : B