Deck 17: Muscle Contraction

Question 1

Thick myofilaments extend the length of the:

A) A-band.
B) Z-line.
C) I-band.
D) None of the above are correct.

Answer 1

A

Question 2

Which of the following proteins found in myofilaments contains the cross-bridges?

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

Answer 2

A

Question 3

A motor unit is most correctly described as a _____ and a motor neuron.

A) sarcomere(s)
B) myofibril(s)
C) muscle fiber(s)
D) filament(s)

Answer 3

C

Question 4

The smallest contractile unit of muscle is a:

A) fiber.
B) myofibril.
C) sarcomere.
D) myofilament.

Question 5

Which of the following is not one of the major functions of muscles?

A) Movement
B) Protection
C) Heat production
D) Posture

Question 6

Skeletal muscles are innervated by:

A) somatic motor neurons.
B) autonomic motor neurons.
C) both somatic and autonomic motor neurons.
D) internal stimulation.

Question 7

Bundles of fine fibers that extend lengthwise along muscle fibers are called:

A) myofibrils.
B) myofilaments.
C) striae.
D) sarcoplasmic reticulum.

Question 8

Most body movements are _____ contractions.

A) isotonic
B) isometric
C) a combination of isotonic and isometric
D) single twitch

Question 9

_____ muscle is also known as striated muscle.

A) Smooth
B) Skeletal
C) Involuntary
D) Visceral

Question 10

The plasma membrane of a muscle fiber is called the:

A) sarcolemma.
B) myofibril.
C) sarcoplasm.
D) sarcomere.

Question 11

The ability of muscle cells to respond to nerve stimuli is called:

A) irritability.
B) contractility.
C) extensibility.
D) elasticity.

Question 12

The neurotransmitter(s) secreted at the motor end plates of skeletal muscles is(are):

A) dopamine.
B) norepinephrine.
C) acetylcholine.
D) any of the above.

Question 13

The first event to occur in muscle relaxation is that:

A) tropomyosin returns to its original position.
B) myosin cross-bridges are prevented from binding to actin.
C) the sarcoplasmic reticulum begins actively pumping calcium back into its sacs.
D) acetylcholine is released.

Question 14

The purpose of creatine phosphate in muscle contraction is to:

A) carry oxygen.
B) store calcium.
C) replenish energy supply.
D) rotate the cross-bridges.

Question 15

The protein molecule that has heads jutting out for cross-bridging is:

A) actin.
B) myosin.
C) troponin.
D) tropomyosin.

Question 16

White fibers are also called _____ fibers.

A) fast
B) slow
C) elongated
D) intermediate

Question 17

In the structure called a triad, the T-tubule is sandwiched between:

A) actin filaments.
B) myofibrils.
C) sarcolemmas.
D) sacs of sarcoplasmic reticulum.

Question 18

The ion necessary for cross-bridging is:

A) iron.
B) sodium.
C) potassium.
D) calcium.

Question 19

Aerobic respiration:

A) allows the body to avoid the use of oxygen for a short time.
B) results in the formation of an incompletely catabolized molecule.
C) results in the formation of lactic acid.
D) produces the maximum amount of energy available from each glucose molecule.

Question 20

The chief function of the T-tubules is to:

A) provide nutrients to the muscle fiber.
B) allow for the fiber to contract.
C) allow for electrical signals to move deeper into the cell.
D) allow for the generation of new muscle fibers.

Question 21

A contraction in which the tension within the muscle remains the same but the length changes is called a(n) _____ contraction.

A) tonic
B) isotonic
C) isometric
D) tetanic

Question 22

Which of the following is not associated with the thin myofilament?

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

Question 23

Which of the following statements is incorrect about motor units?

A) Some motor neurons stimulate only a few dozen muscle fibers.
B) Some motor neurons stimulate a few thousand muscle fibers.
C) The more muscle fibers stimulated by a motor neuron, the more precise the movements of that muscle can be.
D) All of the above statements are correct.

Question 24

The characteristic of the muscle cell that directly causes movement is:

A) excitability.
B) irritability.
C) contractility.
D) extensibility.

Question 25

During which phase of the twitch contraction is there a triggering of the release of calcium ions into the sarcoplasm?

A) Latent period
B) Contraction phase
C) Relaxation phase
D) None of the above

Question 26

All of the following are true characteristics of an isometric contraction except:

A) the muscle does not shorten.
B) it can produce work by tightening to resist a force.
C) movement is produced.
D) the tension produced by the myosin cross-bridges cannot overcome the load placed on the muscle.

Question 27

Cross-bridges are also called:

A) myosin heads.
B) motor end plates.
C) synapses.
D) motor neurons.

Question 28

From smallest to largest, which of the following is the correct order of arrangement?

A) Fiber, myofibril, myofilament
B) Myofibril, myofilament, fiber
C) Myofilament, myofibril, fiber
D) Fiber, myofilament, myofibril

Question 29

Painful muscle contractions or involuntary twitches are called:

A) tetanic contractions.
B) cramps.
C) convulsions.
D) fibrillations.

Question 30

Treppe is also called:

A) tetanus.
B) electromyography.
C) wave summation.
D) staircase phenomenon.

Question 31

The graded strength principle states that:

A) muscle fibers either will contract with all the force possible under existing conditions or will not contract at all.
B) skeletal muscles contract with the same degree of strength at all times, but the force generated is graded.
C) muscle size is indirectly proportional to muscle strength.
D) skeletal muscles contract with varying degrees of strength at different times.

Question 32

Physiological muscle fatigue may be caused by:

A) a relative lack of ATP.
B) high levels of lactic acid.
C) failure of the sodium-potassium pumps.
D) all of the above.

Question 33

The strength of a muscle contraction is influenced by the:

A) amount of load.
B) initial length of muscle fibers.
C) recruitment of motor units.
D) All of the above are correct.

Question 34

Sarcolemma is a:

A) system of transverse tubules that extend at a right angle to the long axis of the cell.
B) segment of the myofibril between two successive Z-lines.
C) unique name for the plasma membrane of a muscle fiber.
D) None of the above are correct.

Question 35

All of the following are characteristics of smooth muscle except:

A) there are no striations.
B) there are no T-tubules.
C) thin and thick filaments are aligned in sarcomeres like skeletal muscles.
D) the sarcoplasmic reticula are loosely organized.

Question 36

A decrease in muscle size is termed:

A) hyperplasia.
B) atrophy.
C) hypertrophy.
D) treppe.

Question 37

Which of the following types of muscle tissue contains cells that have a single nucleus?

A) Cardiac
B) Smooth
C) Skeletal
D) Both A and B

Question 38

Endurance training is also known as:

A) isometrics.
B) hypertrophy.
C) aerobic training.
D) strength training.

Question 39

Attempting to pick up an object too heavy to lift would result in which type of muscle contraction?

A) Isotonic
B) Flaccid
C) Treppe
D) Isometric

Question 40

A sarcomere is a segment of myofibril between two successive:

A) Z-lines.
B) A-bands.
C) I-bands.
D) H-bands.

Question 41

The myofilament that can be described as bundled golf clubs with their heads sticking out from the bundle is:

A) troponin.
B) actin.
C) myosin.
D) tropomyosin.

Question 42

Muscle contractions will continue as long as:

A) the calcium ions are attached to the troponin.
B) there is dopamine in the neuromuscular junction.
C) there is ADP in the muscle cell.
D) T-tubules are transmitting impulses.

Question 43

Which of the following is not an end-product of the breakdown of ATP?

A) An inorganic phosphate
B) Energy that can be used in muscle contraction
C) ADP
D) All of the above are end-products of the breakdown of ATP.

Question 44

The myofibrils contain about how many sarcomeres?

A) 150,000
B) 15,000
C) 1500
D) 150

Question 45

Glucose can be stored in the muscle as:

A) creatine phosphate.
B) ATP.
C) myoglobin.
D) glycogen.

Question 46

Which part of the sarcomere stays almost the same size during contraction?

A) A-band
B) I-band
C) H-band
D) None of the parts of the sarcomere stay the same size during contraction.

Question 47

Which of the following terms describes an isometric contraction?

A) Eccentric contraction
B) Static tension
C) Concentric contraction
D) Both A and C

Question 48

The motor end plate makes up part of the:

A) Z-line.
B) T-tubules.
C) sarcoplasmic reticulum.
D) neuromuscular junction.

Question 49

The lactic acid produced by anaerobic respiration is converted back to glucose in the:

A) lungs.
B) liver.
C) mitochondria.
D) sarcoplasmic reticulum.

Question 50

The striations seen in skeletal muscle cells under the microscope are what part of the sarcomere?

A) Z-lines
B) A-bands
C) I-bands
D) All of the above

Question 51

Which type of muscle is responsible for peristalsis?

A) Multiunit smooth
B) Single-unit smooth
C) Cardiac
D) Striated

Question 52

Which of the following is not a name for a muscle cell?

A) Muscle fiber
B) Sarcocyte
C) Myocyte
D) All of the above are names for muscle cells.

Question 53

Which type of muscle does not have T-tubules?

A) Smooth
B) Cardiac
C) Striated
D) All muscles have T-tubules.

Question 54

Which of the following is not a factor in why a warm muscle contracts more forcefully than a cool muscle?

A) ATP releases energy faster.
B) Calcium diffuses through the sarcoplasm more quickly.
C) Calcium tends to accumulate in the sarcoplasm.
D) All of the above are factors.

Question 55

The myofilament that can be described as a globular protein strung together like beads to form two intertwined strands is:

A) troponin.
B) actin.
C) myosin.
D) tropomyosin.

Question 56

After it is released from the sarcoplasmic reticulum, the calcium combines with which protein?

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

Question 57

Which structure functions to temporarily store calcium ions?

A) T-tubules
B) Sarcolemma
C) Sarcoplasmic reticulum
D) Myofilaments

Question 58

Muscles usually contract to about _____ of their length.

A) 30%
B) 40%
C) 80%
D) 90%

Question 59

The substance that attracts oxygen in the myoglobin molecule is:

A) hemoglobin.
B) calcium.
C) iron.
D) ATP.

Question 60

A satellite cell in a muscle can become active:

A) during isotonic contractions.
B) during isometric contractions.
C) after an injury to a muscle.
D) when a muscle becomes fatigued.

Question 61

Which of the following is not a part of the neuromuscular junction?

A) T-tubules
B) Motor neuron
C) Motor end plate
D) All of the structures are part of the neuromuscular junction.

Question 62

A neuromuscular junction is a type of connection called a synapse.

Question 63

Which of the following statements about cardiac muscle is incorrect?

A) Cardiac muscle requires nervous stimulation to contract.
B) Cardiac muscle is also called striated involuntary muscle.
C) Cardiac muscle contains intercalated disks.
D) All of the above statements are correct.

Question 64

Hemoglobin carries oxygen in red blood cells, and myoglobin stores oxygen in muscle fibers.

Question 65

T-tubules are perpendicular to muscle fibers.

Question 66

Anaerobic respiration is the first choice of the muscle cell for the production of ATP.

Question 67

The following are characteristics that allow muscles to function as they do: excitability, contractility, extensibility, and regulation.

Question 68

Myofibrils contain several sarcomeres lined up end to end.

Question 69

Muscle fibers use creatine phosphate to restore their ATP population.

Question 70

Which of the following is an incorrect statement regarding heat production?

A) The body temperature set point is established by the hypothalamus.
B) Shivering will increase body temperature.
C) Body temperature functions on a negative-feedback mechanism.
D) All of the above are correct.

Question 71

The sliding-filament theory is the current model of muscle contraction.

Question 72

The protein molecule that has heads jutting out for cross-bridging is called myosin.

Question 73

A triad consists of a T-tubule sandwiched between sacs of the sarcoplasmic reticulum.

Question 74

Muscle fibers of skeletal muscle contain several nuclei.

Question 75

The cell membrane of a muscle fiber is called the sarcoplasmic reticulum.

Question 76

Another name for muscle cells is muscle fibers.

Question 77

Muscle cells have one nucleus and one mitochondrion.

Question 78

Which of the following statements about cardiac muscle is incorrect?

A) Cardiac muscle forms an electrically coupled mass called a syncytium.
B) Much of the calcium necessary for contraction comes from outside the cell.
C) In cardiac muscles, the T-tubules form dyads rather than the triads formed in skeletal muscles.
D) All of the above statements are correct.

Question 79

Which of the following statements is incorrect regarding muscle tone?

A) Tonic contractions is another name for muscle tone.
B) Muscle tone is important in maintaining posture.
C) Muscles with less than normal muscle tone are referred to as spastic.
D) All of the above statements are correct.

Question 80

ATP is made up of adenine, ribose sugar, and three phosphate groups.