Deck 8: Muscle Physiology

Question 1

A function of tropomyosin is

A) bind Ca²⁺.
B) form attachments with myosin cross bridges.
C) prevent myosin cross bridges from attaching to the thin filaments.
D) serve as an ATPase.
E) none of these answers.

Answer 1

prevent myosin cross bridges from attaching to the thin filaments.

Question 2

Z lines

A) are formed by the T tubules.
B) extend down the middle of the I band.
C) are formed by the cross bridges.
D) are the thin filaments.
E) extend down the middle of the sarcomere.

Answer 2

extend down the middle of the I band.

Question 3

The Z line of the sarcomere is characterized by

A) overlapping thin and thick filaments.
B) only thick filaments.
C) only thin filaments.
D) a very dark coloration.
E) none of these answers.

Answer 3

none of these answers.

Question 4

The light and dark bands of a sarcomere are generated by the overlap of:

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

Question 5

Myosin is

A) spherical.
B) the main structural component of the thick filaments.
C) is referred to as a regulatory protein.
D) all of these answers.
E) none of these answers.

Question 6

Troponin

A) binds with calcium to prevent sarcomere shortening.
B) breaks down actin.
C) breaks down myosin.
D) forms the boundaries of a sarcomere.
E) is an enzyme in the sarcomere.

Question 7

Which of the following statements concerning cross bridges is not correct? Cross bridges

A) cross bridges bind to actin during muscle contraction.
B) cross bridges are formed by the globular heads of the myosin molecules.
C) formation is tied to Cl^- levels in the cytosol
D) cross bridges bend during muscle contraction.
E) cross bridges protrude from the thick filaments.

Question 8

Actin

A) has ATPase activity.
B) is spherical.
C) forms a helical chain that forms the main structural component of the thin filaments.
D) two of these answers.
E) all of these answers.

Question 9

Actin

A) is spherical.
B) contains a globular head that forms the cross bridges between the thick and thin filaments.
C) is referred to as a regulatory protein.
D) is inhibited by Ca2+.
E) none of these answers.

Question 10

The striated appearance of skeletal muscle is due to the

A) regular orderly arrangement of the T tubules.
B) regular orderly arrangement of the lateral sacs of the sarcoplasmic reticulum.
C) regular orderly arrangement of the thick and thin filaments into A and I bands.
D) regular orderly arrangement of the motor units.
E) presence of white and red muscle fibers within the muscle.

Question 11

Which protein contributes to the elasticity of the sarcomere?

A) actin
B) myosin
C) troponin
D) tropomysosin
E) titin

Question 12

Myosin

A) is found in the A band.
B) is found in the I band.
C) is the primary protein found in the thin filaments.
D) contracts during muscle contraction because it is one of the contractile proteins.
E) none of these answers.

Question 13

Which of the following characteristics are shared by all three types of muscle tissues?

A) each one contains myosin and actin.
B) each one is neurogenic.
C) each one is striated.
D) each one is considered to be under voluntary control.
E) none of these answers.

Question 14

The functional unit of skeletal muscle is the

A) lengthens when the muscle contracts
B) area between two Z lines.
C) consists of just actin and myosin
D) two of these answers.
E) all of these answers.

Question 15

Muscle fibers develop tension by

A) contraction of sarcomeres.
B) shortening.
C) the pushing of myosin by actin.
D) both (a) and (b) above.
E) none of these answer.

Question 16

The region between two Z lines is a

A) muscle fiber.
B) myofibril.
C) myofilament.
D) sarcomere.
E) sarcoplasmic reticulum.

Question 17

Sarcomeres are arranged end to end as

A) fascicles.
B) myofibrils.
C) bands.
D) perimysium.
E) none of these answers.

Question 18

Order the following muscle cell components from larger to smaller 1 troponin
2 myofibril
3 sarcomere
4 thin filament
5 muscle fiber

A) 3, 4, 1, 5, 2
B) 1, 2, 3, 5, 4
C) 5, 4 ,3 , 1, 2
D) 5, 2, 3, 4, 1
E) 3, 4, 5, 2, 1

Question 19

Thin filaments in skeletal muscle are composed of

A) actin.
B) troponin and tropomysosin.
C) myosin.
D) actin, troponin, and tropomyosin.
E) all of these answers.

Question 20

The striated appearance of skeletal muscle is due to the

A) regular arrangement of the T tubules running transversely through the muscle fiber.
B) presence of the Z lines extending down the middle of the I bands.
C) presence of gap junctions.
D) regular arrangement of the motor units.
E) none of these answers.

Question 21

Of the step in excitation-contraction below, which occurs before the others?

A) exposed actin sites bind with myosin cross bridges.
B) sodium channels open in the fiber's membrane.
C) calcium is released from the sarcoplasmic reticulum.
D) troponin binds calcium.
E) attachment of ATP allows for cross bridge detachment.

Question 22

The sarcolemma

A) is the muscle cell plasma membrane
B) provide a means of rapidly transmitting the action potential from the surface into the central portions of the muscle fiber.
C) store ATP.
D) run longitudinally between the myofibrils.
E) have expanded lateral sacs.

Question 23

An action potential rapidly spreads to the central portions of a muscle cell by means of the

A) Z lines.
B) sarcoplasmic reticulum.
C) H zone.
D) pores in the membrane surface.
E) T tubules.

Question 24

The T tubules

A) form the Z lines.
B) store Ca²⁺.
C) provide a means of rapidly transmitting the action potential to the central portions of the muscle fiber.
D) allow for nutrients to be carried into the cell.
E) none of these answers.

Question 25

Binding of ____ to myosin permits cross-bridge ____ between actin and myosin.

A) ATP, binding.
B) ATP, detachment.
C) calcium, binding.
D) calcium, detachment.
E) none of these answers.

Question 26

This structure provide a means of rapidly transmitting the action potential to the central portions of the muscle fiber.

A) T-tubule
B) sarcoplasmic reticulum
C) Z lines
D) myofibril
E) myofilaments

Question 27

During contraction, asynchronous cycling of crossbridges

A) prevents tetany.
B) prevents thick filaments from slipping backwards.
C) prevents thin filaments from slipping backwards.
D) utilizes less ATP.
E) none of these answers.

Question 28

Sequence the following events involved in muscle cell contraction

A) 1, 2, 3, 4, 5
B) 2, 1, 3, 4, 5
C) 2, 4, 3, 1, 5
D) 3, 4, 5, 1, 2
E) 3, 5, 2, 1, 4

Question 29

Which is characteristic of cross bridges?

A) they are a component of thick filaments.
B) they are comprised of actin
C) they have an troponin binding site.
D) they attach to Z lines
E) they allow shortening of the muscle proteins

Question 30

This molecule allows crossbridge detachment:

A) ATP
B) sodium
C) actin
D) calcium
E) acetylcholine

Question 31

Which molecules are involved with regulation of cross bridge attachment activity?

A) calcium ions.
B) troponin.
C) tropomyosin.
D) both (a) and (b) above.
E) all these answers.

Question 32

The H zone

A) is the area within the middle of the A band where the thin filaments do not reach.
B) shortens or disappears during contraction.
C) contains only thick filaments.
D) both (a) and (b) above.
E) all of these answers.

Question 33

During excitation-contraction coupling,

A) the action potential travels down the transverse tubules.
B) Ca²⁺ is released from the sarcoplasmic reticulum.
C) Ca²⁺ is taken up by the sarcoplasmic reticulum.
D) both (a) and (b) above are correct.
E) all of these answers.

Question 34

During muscle contraction, the

A) contractile proteins contract.
B) contractile proteins shorten
C) A band becomes smaller
D) I band remains unchanged.
E) amount of calcium in the cytosol remains constant

Question 35

During contraction of skeletal muscle fibers, the

A) contractile proteins contract.
B) thin filaments slide inward toward the A band's center as a result of cycles of cross-bridge binding and bending.
C) thick and thin filaments become tightly coiled, thus shortening the sarcomere.
D) I bands slide in between the A bands.
E) lateral sacs of the sarcoplasmic reticulum shrink, pulling the Z lines closer together.

Question 36

The sarcoplasmic reticulum stores ____ when a muscle is relaxed and releases it for binding to ____ during contraction.

A) calcium, troponin
B) calcium, tropomyosin
C) sodium, tropomyosin
D) potassium, tropomyosin
E) sodium, troponin

Question 37

Which is not characteristic of cross bridges?

A) they are a component of thin filaments.
B) they are comprised of myosin.
C) they have an actin binding site.
D) they have an ATPase binding site.
E) they provide power stroking.

Question 38

Which of the following changes in banding pattern occur during muscle contraction?

A) the A band gets shorter.
B) the I band gets shorter.
C) the H zone gets shorter.
D) both the I band and the H zone get shorter.
E) all of these answers.

Question 39

According to the sliding-filament mechanism of muscle contraction, the

A) A bands slide in closer between the I bands.
B) thin filaments slide inward toward the center of the A band.
C) Z lines slide in between the T tubules.
D) contractile proteins contract, thus shortening the sarcomere.
E) filaments slide into the lateral sacs of the sarcoplasmic reticulum.

Question 40

Of the step in excitation-contraction below, which occurs last?

A) exposed actin sites bind with myosin cross bridges.
B) sodium channels open in the fiber's membrane.
C) calcium is released from the sarcoplasmic reticulum.
D) troponin binds calcium.
E) attachment of ATP allows for cross bridge detachment.

Question 41

Which of the following is involved in the process of muscle relaxation

A) acetylcholinesterase destroys acetylcholine to allow the muscle membrane to return to resting potential.
B) Ca²⁺ is released by the sarcoplasmic reticulum
C) cross bridge formation increases
D) both (a) and (b) above.
E) all of these answers.

Question 42

Which of the following is not a method of gradation of skeletal muscle contraction?

A) twitch summation
B) motor unit recruitment
C) stimulating variable portions of each motor unit
D) varying the number of motor units stimulated
E) varying the frequency at which a motor unit is stimulated

Question 43

Which of the following is not a determinant of whole muscle tension?

A) the number of muscle fibers contracting.
B) the tension produced by each contracting fiber.
C) the extent of motor-unit recruitment.
D) the frequency of stimulation.
E) the proportion of each motor unit that is contracting at any given time.

Question 44

Summation

A) results from increases in cystolic calcium levels.
B) a decreased in the rate of firing of the motor neuron
C) produces weaker than normal contractions
D) rarely results in tetany.
E) none of these answers.

Question 45

A motor unit refers to

A) a single motor neuron plus all of the muscle fibers it innervates.
B) a single muscle fiber plus all of the motor neurons that innervate it.
C) all of the motor neurons supplying a single muscle.
D) a pair of antagonistic muscles.
E) a sheet of smooth muscle cells connected by gap junctions.

Question 46

Which of the following is not involved in the relaxation of muscle?

A) when acetylcholine is destroyed by acetylcholinesterase.
B) when there is no longer a local action potential.
C) when the T tubules actively take up the Ca²⁺ that had been released.
D) when the actin and myosin molecules are no longer bound together.
E) when the troponin-tropomyosin complex slips back into its blocking position.

Question 47

Which of the following characteristics associated with twitch summation allows for maximal contraction force?

A) high levels of NE in the synapse
B) lower frequency of action potentials in the sarcolemma
C) increased movement of calcium into the sarcoplasmic reticulum
D) rapid rise of calcium in the cytosol
E) longer latent periods of contractions

Question 48

A motor unit has a small number of muscle fibers. Which of the following would likely be true of this motor unit. It:

A) is can produce a great amount of forces
B) is associated with muscles of the lower back
C) is involved in delicate contractions
D) has companion motor units that likely have many muscle fibers
E) is a sheet of smooth muscle cells connected by gap junctions.

Question 49

Which of the following is involved in the process of muscle relaxation

A) acetylcholinesterase destroys acetylcholine to allow the muscle membrane to return to resting potential.
B) Ca²⁺ is actively taken up by the lateral sacs of the sarcoplasmic reticulum when there is no longer a local action potential.
C) the cross bridges from the thick filaments bind to the thin filaments and bend in such a way as to return the filaments to their original resting position.
D) both (a) and (b) above.
E) all of these answers.

Question 50

Which of the following is involved in the gradation of muscle contraction?

A) variation in the number of motor units activated
B) variation in the frequency of action potentials initiated in each muscle fiber
C) variation in the size of the action potentials initiated in each muscle fiber
D) both (a) and (b) above.
E) all of these answers.

Question 51

During a cross-bridge cycle in skeletal muscle, the

A) cross bridge is energized as myosin ATPase activity hydrolyzes ATP.
B) myosin cross bridge is able to bind with an actin molecule when Ca²⁺ pulls the troponin-tropomyosin complex aside.
C) linkage between actin and the myosin cross bridge is broken at the end of the cross-bridge cycle as Mg²⁺ binds to the cross bridge.
D) both (a) and (b) above.
E) all of these answers.

Question 52

In twitch summation,

A) the muscle fiber is stimulated again before the action potential has returned to resting potential.
B) the muscle fiber is stimulated again before the filaments have completely returned to their resting position.
C) stronger muscle contractions occur but stronger action potentials do not occur.
D) both (b) and (c) above.
E) all of these answers.

Question 53

Why are you able to repeatedly contract and relax your muscles of respiration, allowing you to breathe in and breathe out?

A) As soon as all of the Ca²⁺ stored in the lateral sacs of the sarcoplasmic reticulum is used up, muscle relaxation occurs.
B) After the muscle cell becomes excited, acetylcholinesterase rapidly destroys acetylcholine.
C) When there is no longer a local action potential in the muscle cell, Ca²⁺ is actively transported back into the lateral sacs of the sarcoplasmic reticulum, and muscle relaxation occurs.
D) Both (b) and (c) above.
E) All of these answers.

Question 54

Twitch summation

A) is a means by which gradation of muscle contraction may be accomplished.
B) results from increasing the number of motor units that are firing within a muscle.
C) results from increasing the frequency at which motor units are firing within a muscle.
D) both (a) and (b) above.
E) both (a) and (c) above.

Question 55

What would happen if ATP supplies became very low in a muscle cell?

A) tension development would decrease.
B) cross bridges would not detach from actin.
C) possibly contractures.
D) in death, rigor mortis.
E) all these answers.

Question 56

Cross bridge interaction between actin and myosin in skeletal muscle is directly blocked by

A) acetylcholine.
B) triads.
C) Z lines.
D) calcium.
E) tropomyosin.

Question 57

If you wanted to pick up something heavier than your pencil (such as your book), you would need to have a stronger muscle contraction. In what way might you accomplish this?

A) stimulate more motor units
B) decrease the frequency of stimulation to allow a more prolonged contraction to occur
C) decrease the refractory period
D) block acetylcholinesterase at the neuromuscular junction to allow acetylcholine to function longer
E) none of these answers.

Question 58

Cross bridges

A) extend between the A and I bands and bend to pull the bands together during muscle contraction.
B) are formed by the globular heads of the myosin molecules.
C) link troponin and tropomyosin to actin to form the thin filament.
D) extend from the thick filaments and bind to actin, then bend to pull the thin filaments in closer together during muscle contraction.
E) two of these answers.

Question 59

The energy for cross bridge cycling during muscle contraction is provided by

A) acetylcholine.
B) Ca²⁺.
C) ATP.
D) myosin.
E) actin.

Question 60

Which of the following results in muscle relaxation?

A) addition of magnesium to muscle cells.
B) AChE activity.
C) return of calcium to lateral sacs.
D) sliding together of thick and thin filaments.
E) two of these answers.

Question 61

Myoglobin

A) can store small amounts of O₂.
B) increases the rate of O₂ transfer from the blood into muscle fibers.
C) is abundant in fast-glycolytic fibers.
D) both (a) and (b) above.
E) all of these answers.

Question 62

Which of the following properties characterize fast-oxidative muscle fibers?

A) high myosin-ATPase activity
B) low myosin-ATPase activity
C) low oxidative capacity
D) both high myosin-ATPase activity and low oxidative capacity are correct.
E) both low myosin-ATPase activity and low oxidative capacity.

Question 63

Energy sources available to form ATP in muscle fibers are below. Which statement is correct?
1. phosphorylation of ADP by creatine phosphate
2. oxidative phosphorylation of ADP in the mitochondria
3. phosphorylation of ADP by the glycolytic pathway in the cytosol

A) (1) and (2) produce the same amount of ATP
B) (1) is the first sourced utilize to supply ATP to a contracting muscle
C) (1) and (3) are considered aerobic
D) (1) and (2) occur in the mitochondria
E) none of these answers.

Question 64

Which of the following statements concerning the characteristics of different types of muscle fibers is incorrect?

A) the higher the ATPase activity, the faster the speed of contraction.
B) muscles that have high glycolytic capacity and large glycogen stores are more resistant to fatigue.
C) muscles with high ATP-synthesizing ability are more resistant to fatigue.
D) oxidative types of muscle fibers contain myoglobin.
E) muscle fibers containing large amounts of myoglobin have a dark red color in comparison to the paler fibers, which have little myoglobin.

Question 65

During aerobic exercise what is the primary means by which ATP is produced for contractile activity?

A) creatine phosphate.
B) fermentation.
C) oxidative phosphorylation.
D) glycolysis.
E) myoglobin.

Question 66

In a muscle fiber undergoing maximal tetanic stimulation, the velocity of shortening ____ as the load ____.

A) decreases, decreases.
B) decreases, increases.
C) increases, increases.
D) remains constant, increases.
E) remains constant, decreases.

Question 67

The origin of a muscle is its

A) main, thick part of this structure.
B) middle, thin part of this structure.
C) movable end of attachment.
D) source of development in the fetus.
E) stationary end of attachment.

Question 68

Submaximal isometric contractions are important for

A) moving large objects.
B) walking.
C) maintaining posture.
D) writing.
E) none of these answers.

Question 69

Which of the following is a characteristic of isometric muscle contractions?

A) they occur at constant tension.
B) the muscle shortens.
C) they are used for body movements.
D) they occur at constant length.
E) the external muscle tension is greater than the load.

Question 70

During an isotonic contraction of a muscle in the arm

A) filaments do not shorten in the muscle.
B) movement does not occur.
C) the muscle does not change length.
D) the tension in the muscle does not overcome a load.
E) the tension in the muscle remains constant.

Question 71

Muscle tension

A) is created during muscle contraction as the tension generated by the contractile elements is transmitted via the connective tissue and tendons to the bones.
B) is the force exerted on a muscle by the weight of an object.
C) is greater than the load during an isometric contraction.
D) more than one of these.
E) none of these answers.

Question 72

With eccentric muscle contractions,

A) the development of tension occurs at constant muscle length.
B) the muscle lengthens while contracting.
C) the muscle shortens while contracting.
D) muscle length and tension vary throughout a range of motion.
E) none of these answers.

Question 73

If the load on a muscle is increased, eventually a load will be reached at which the velocity of shortening becomes zero. At this point, the muscle contraction is referred to as

A) concentric.
B) eccentric.
C) isotonic.
D) isokinetic.
E) isometric.

Question 74

If a skeletal muscle is lengthened significantly beyond its resting length:

A) muscle tension is increased
B) the muscle cannot shorten during contraction.
C) at this state, the muscle will produce a force less than normal
D) no change will occur
E) only smooth muscle can be stretched beyond its resting length

Question 75

Select the correct statement about the summation of simple twitches.

A) They can occur from the long duration of the action potential in a muscle fiber.
B) They reduce the tension in a muscle.
C) They result from the slow stimulation of a muscle fiber.
D) The effect is unrelated to the refractory periods of action potentials.
E) The twitches from action potentials add together.

Question 76

Which of the following statements concerning the length-tension relationship is incorrect?

A) It refers to the relationship between the length of the muscle before the onset of contraction and the tetanic tension that each contracting fiber can subsequently develop at that length.
B) it is based on the amount of overlap of thick and thin filaments.
C) it allows no tension development if the whole muscle is stretched to 30% longer than its optimal length.
D) within the body, it is limited to a functional range because of limitations on muscle length imposed by attachment to the skeleton.
E) none of these answers.

Question 77

The first means by which ATP is produced at the onset of contractile activity is

A) transfer of energy and phosphate from creatine phosphate to ADP.
B) oxidative phosphorylation.
C) glycolysis.
D) degradation of myoglobin.
E) none of these answers.

Question 78

Energy sources available to form ATP in muscle fibers are
1. phosphorylation of ADP by creatine phosphate
2. oxidative phosphorylation of ADP in the mitochondria
3. phosphorylation of ADP by the glycolytic pathway in the cytosol

A) (1) and (2) are correct.
B) (2) and (3) are correct.
C) (1) and (3) are correct.
D) (1), (2), and (3) are correct.
E) none of these answers.

Question 79

Which of the following statements concerning the length-tension relationship of skeletal muscle is incorrect?

A) when a muscle is maximally stretched, it can develop the most tension upon contraction because the thin filaments can slide in a maximal distance.
B) maximum tension can be developed if the muscle is at its lowest at the onset of contraction.
C) in the body, the relaxed length of muscle is at its optimal length.
D) when the initial length of muscle prior to contraction becomes very short, tension is decreased during contraction because of thin filament overlap, because the thick filaments are compressed against the Z lines, and because not as much Ca2+ is released during excitation-contraction coupling.
E) the tension that can be achieved during a tetanic contraction is less when a muscle is shorter or longer than its optimal length at the onset of contraction.

Question 80

The insertion of a muscle

A) is only associated with smooth muscle
B) contains muscle spindles
C) is the movable end of attachment.
D) source of development in the fetus.
E) serves the same function as the origin