Deck 12: Muscles

Question 1

The molecular event that occurs immediately after the power stroke is the

A) release of actin from the myosin head.
B) hydrolysis of ATP by the myosin head.
C) release of ADP from the myosin.
D) binding of tropomyosin to the myosin.
E) binding of actin to the myosin.

Answer 1

C

Question 2

A flexor is a skeletal muscle whose shortening moves attached bones

A) away from one another.
B) towards one another.
C) medially.
D) laterally.

Answer 2

B

Question 3

When a skeletal muscle generates enough force during contraction to shorten,

A) only the sarcomere will shorten.
B) only the A band will shorten.
C) only the I band will shorten.
D) the sarcomere and the I band will shorten.
E) the sarcomere, the A band, and the I band will shorten.

Answer 3

D

Question 4

Each myosin head has a binding site for

A) calcium only.
B) actin only.
C) ATP only.
D) calcium and ATP.
E) actin and ATP.

Question 5

Striated muscles are so-called because of a repeating pattern of light and dark bands.One repeating unit of the banding pattern is called a

A) myofilament.
B) myomere.
C) sarcofibril.
D) sarcomere.
E) crossbridge.

Question 6

Which of the following would cause the crossbridge to transition from a high force state to a low force state?

A) increasing myosin ATPase activity
B) increasing intracellular calcium
C) decreasing intracellular calcium
D) energizing the myosin head
E) decreasing myosin ATPase activity

Question 7

The origin is the end of the skeletal muscle that attaches to the

A) more stationary bone.
B) more mobile bone.
C) tendon.
D) ligament.

Question 8

When a skeletal muscle cell contracts and the muscle shortens,

A) myosin heads generate a single power stroke.
B) the position of an actin molecule relative to a myosin molecule does not change.
C) some myosin heads are forming crossbridges as others are releasing them.
D) the actin ATPase allows the actin molecule to swivel.
E) the actin molecule swivels during the power stroke.

Question 9

Most of the time, the parallel thick and thin filaments of the myofibrils are connected by ________ that span the space between myosin and actin molecules.

A) tropomyosin molecules
B) crossbridges
C) nebulin molecules
D) sarcomeres
E) calcium ions

Question 10

________ is composed of multiple globular molecules polymerized to form long chains or filaments.

A) Actin
B) Tropomyosin
C) Troponin
D) Myosin
E) Titin

Question 11

The I band contains

A) thick filaments only.
B) thin filaments only.
C) myosin only.
D) thick and thin filaments.

Question 12

For antagonistic muscle groups to move a limb, flexor contraction occurs coincident with

A) contraction of the extensor.
B) relaxation of the extensor.
C) no changes in the extensor.
D) contraction of the tendon.

Question 13

The function of the titin protein is to

A) stabilize the position of the contractile filaments.
B) pull Z lines together during contraction.
C) interact with actin during contraction.
D) release calcium during contraction.
E) cover the myosin binding site on the actin molecule.

Question 14

Skeletal muscle cells are usually attached to bone by

A) fascicles.
B) ligaments.
C) tendons.
D) flexors.

Question 15

The H zone contains

A) thick filaments.
B) thin filaments only.
C) actin only.
D) thick and thin filaments.

Question 16

In order for high force crossbridges to form in contracting skeletal muscle, calcium must

A) bind to calmodulin to phosphorylate the myosin.
B) phosphorylate the tropomyosin which moves it.
C) phosphorylate the troponin to move the tropomyosin.
D) bind to tropomyosin which moves the troponin.
E) bind to troponin which moves the tropomyosin.

Question 17

The tension generated in a skeletal muscle fiber is directly proportional to the number of

A) thick and thin filaments present.
B) nebulin and titin molecules present.
C) high-energy crossbridges formed.
D) low-energy crossbridges formed.
E) active sarcomeres.

Question 18

The function of transverse tubules is to

A) store Ca²⁺ ions inside the muscle fiber.
B) rapidly conduct action potentials to the interior of the muscle fiber.
C) ensure a supply of glycogen throughout the muscle sarcoplasm.
D) conduct ATP molecules out of the mitochondria throughout the sarcoplasm.

Question 19

The hydrolysis of ATP causes myosin to immediately

A) swivel, moving the actin molecule.
B) release ADP.
C) release from the actin.
D) rotate into a position (cocked) to bind to actin.
E) bind more tightly to the actin (rigor).

Question 20

As ATP binds to the myosin head at the beginning of a muscle contraction cycle, the myosin head immediately

A) detaches from actin.
B) initiates binding with actin.
C) tightens its bond to actin.
D) swivels.

Question 21

Which fibers fatigue sooner?

A) fast-twitch fibers
B) slow-twitch fibers

Question 22

The contraction cycle is triggered by the rise in ________ released from the sarcoplasmic reticulum (SR).

A) Na⁺
B) K⁺
C) Ca²⁺

Question 23

The action potential traveling along the t-tubule is detected by the

A) ryanodine receptor.
B) dihydropyridine (DHP) receptor (L-type calcium channel).
C) acetylcholine receptor.
D) Ca²⁺ ATPase.

Question 24

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.

Question 25

A motor unit consists of

A) one neuron and all the skeletal muscle fibers it controls.
B) one skeletal muscle fiber and all the neurons that control that fiber.
C) one skeletal muscle fiber and the neuron that controls that fiber.
D) one axon terminal branch and the myofibrils it controls.

Question 26

The binding of acetylcholine to its receptor at the neuromuscular junction causes the opening of a

A) Na⁺ channel.
B) channel for both Na⁺ and K⁺.
C) calcium channel.
D) ryanodine receptor.

Question 27

The relaxation of skeletal muscle relies on the activity of the ________, which decreases cytoplasmic calcium concentration.

A) ryanodine receptor
B) dihydropyridine (DHP) receptor (L-type calcium channel)
C) acetylcholine receptor
D) Ca²⁺ ATPase

Question 28

Motor units that control skeletal muscles involved with fine motor movements (eye muscles or the hands)have ________ muscle fibers than motor units that control more gross movements (gastrocnemius muscle of the lower leg).

A) more
B) fewer
C) the same number of

Question 29

During heavy exercise, the ATP requirements of active muscle are likely to be met by metabolism of

A) protein.
B) fatty acids.
C) carbohydrates.
D) nucleotides.

Question 30

The speed with which force is developed by skeletal muscles is determined by the

A) Ca²⁺ ATPase activity.
B) sarcoplasmic calcium concentration.
C) myosin ATPase isoform.
D) Ca²⁺ ATPase activity and sarcoplasmic calcium concentration.
E) Ca²⁺ ATPase activity, myosin ATPase isoform, and sarcoplasmic calcium concentration.

Question 31

When comparing complete tetanus with unfused (incomplete)tetanus, which is True?

A) Complete tetanus involves some relaxation between twitches.
B) Complete tetanus involves development of maximum tension.
C) Complete tetanus occurs at a lower frequency of stimulation than unfused tetanus.
D) Complete tetanus would occur when there is more time between twitch contractions.

Question 32

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

Question 33

The brief period of time between the beginning of the action potential in the muscle and the beginning of contraction is referred to as the

A) refractory period.
B) latent period.
C) relaxation phase.
D) depolarization period.
E) repolarization period.

Question 34

The cause of skeletal muscle fatigue during extended submaximal exercise is primarily a(n)

A) depletion of glycogen stores.
B) depletion of creatine stores.
C) increased inorganic phosphate (Pi) concentration.
D) depletion of K⁺ stores.

Question 35

Which of the following is a characteristic of slow-twitch oxidative skeletal muscle fibers?

A) long contraction duration only
B) few mitochondria only
C) high capillary density only
D) long contraction duration and high capillary density
E) long contraction duration, few mitochondria, and high capillary density

Question 36

Which fibers generate more force?

A) fast-twitch fibers
B) slow-twitch fibers

Question 37

Muscle fatigue arises primarily from failure in

A) neuromuscular transmission.
B) initiation of contraction by the motor cortex.
C) excitation-contraction coupling.
D) signal relay from brain to spinal cord.
E) calcium pumps in the skeletal muscles.

Question 38

Within a single fiber, the tension developed during a twitch depends upon the

A) amplitude of the action potential.
B) length of the sarcomeres prior to contraction.
C) length of the thick filament.
D) duration of the stimulus.

Question 39

________ is the backup energy molecule that can be rapidly converted to ATP in active skeletal muscle.

A) Protein
B) Glucose
C) Fatty acid
D) Phosphocreatine

Question 40

Which of the following statements is NOT correct regarding the motor units and their activation?

A) A motor unit in muscles of gross movement can have thousands of muscle cells.
B) All muscle fibers in a single motor unit are of the same fiber type.
C) A weak contractile stimulus activates fast-twitch motor units.
D) The metabolic capacity of muscle fibers within a motor unit can be altered.
E) At its peak intensity, a contractile stimulus will activate muscle fibers that are easily fatigued.

Question 41

Match the structures with the accurate description.
A.muscle fiber
B.fascicle
C.sarcolemma
D.myofibril
E.t-tubules
a bundle of adjacent muscle cells

Question 42

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

Question 43

Match the structures with the accurate description.
A.muscle fiber
B.fascicle
C.sarcolemma
D.myofibril
E.t-tubules
the muscle cell membrane

Question 44

Match from the following list.
A.A band
B.I band
C.Z disk
D.H zone
E.M line
The letter assigned to this structure stands for the German word for middle; it is the attachment site for the thick filaments.

Question 45

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

Question 46

Match from the following list.
A.A band
B.I band
C.Z disk
D.H zone
E.M line
The structures that serve as the attachment site for the thin filaments and mark the boundaries for one sarcomere.

Question 47

Match the structures with the accurate description.
A.muscle fiber
B.fascicle
C.sarcolemma
D.myofibril
E.t-tubules
a single muscle cell

Question 48

Match from the following list.
A.A band
B.I band
C.Z disk
D.H zone
E.M line
The band with the most overlap between thick and thin filaments, which unevenly scatters light leading to its' dark appearance.

Question 49

Match the structures with the accurate description.
A.muscle fiber
B.fascicle
C.sarcolemma
D.myofibril
E.t-tubules
inward extensions of the muscle cell membrane

Question 50

Match the structures with the accurate description.
A.muscle fiber
B.fascicle
C.sarcolemma
D.myofibril
E.t-tubules
highly organized bundles of contractile proteins within a skeletal muscle cell

Question 51

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.

Question 52

Smooth muscle cells lack which protein(s)?

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

Question 53

Match from the following list.
A.A band
B.I band
C.Z disk
D.H zone
E.M line
The lightest color bands of the sarcomere, comprised only of thin filaments.

Question 54

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.

Question 55

What are the three types of muscle tissues in the human body? What are the two common functions of muscles?

Question 56

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

Question 57

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.

Question 58

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

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

Question 59

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.

Question 60

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.

Question 61

Store-operated calcium channels open in response to ________.

Question 62

Groups of adjacent fibers bundled together into units are called ________.These bundles are surrounded by the proteins ________ and elastin as well as ________ that deliver nutrients to the muscle cells.

Question 63

Smooth muscle fibers can sustain a contraction without fatigue by allowing dephosphorylated myosin to remain attached to actin in what is called the ________.

Question 64

A(n)________ contraction describes the opening of stretch-activated channels in smooth muscle cells in response to a distortion of the cell membrane that is commonly observed in ________.

Question 65

The gap junctions in cardiac muscle are part of specialized cell junctions that are localized to the ________.

Question 66

The T-tubular membrane contains ________ receptors that are ________ and therefore respond to action potentials.This receptor is mechanically linked to ________ receptors in the adjacent sarcoplasmic reticulum.

Question 67

________ and ________ are striated muscles.Why are these muscles classified as striated muscles?

Question 68

Asynchronous activation of motor units is important because it functions to ________.

Question 69

The thick filament of the myofibril is composed of ________ molecules whereas ________ is a protein that makes up the thin filaments.

Question 70

Calcium, released by the sarcoplasmic reticulum, binds to ________ to move the ________, which allows actin to form of a ________ with myosin.

Question 71

In order to contract and relax, muscle cells require energy in the form of ________.The immediate backup energy source is ________ that requires the enzyme ________.

Question 72

In smooth muscle cells, Ca²⁺ binds to ________ which activates the enzyme ________ to phosphorylate myosin and increase force.

Question 73

In comparison to skeletal muscle, smooth muscle cells function over a ________ range of muscle lengths and exhibit a speed of contraction that is ________ than skeletal muscle.

Question 74

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

Question 75

The reductions in muscle force generation at lengths different from optimal are a result of a(n)________.

Question 76

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

Question 77

Fatigue that occurs in response to extended submaximal exertion is usually due to ________ whereas fatigue to a short duration of maximal exertion involves ________.

Question 78

As a muscle cell undergoes an eccentric contraction, sarcomere length will ________ as the length of the A band ________.

Question 79

The heavy chain of myosin contains two important regions: the first acts as ________ to convert energy into movement whereas the second binds to ________.

Question 80

In fast-twitch oxidative-glycolytic fibers, their rapid increases in force rely on the ________ activity where rapid relaxation requires ________ activity.