CHAPTER 17- Muscle Contraction

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.

a. A-band

Thick myofilaments extend the length of the: a. A-band. b. Z-line. c. I-band. d. None of the above are correct.

a. A-band.

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. More actin-myosin reactions occur.

a. ATP releases energy faster.

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.

a. Cardiac muscle requires nervous stimulation to contract.

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

a. Latent period

Which of the following proteins found in myofilaments contains the cross-bridges? a. Myosin b. Actin c. Tropomyosin d. Troponin

a. Myosin

Which type of muscle does not have T-tubules? a. Smooth b. Cardiac c. Striated d. All muscles have T-tubules.

a. Smooth

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.

a. T-tubules

After it is released from the sarcoplasmic reticulum, the calcium combines with which protein? a. Troponin b. Actin c. Myosin d. Tropomyosin

a. Troponin

A sarcomere is a segment of myofibril between two successive: a. Z-lines. b. A-bands. c. I-bands. d. H-bands.

a. Z-lines.

White fibers are also called _____ fibers. a. fast b. slow c. elongated d. intermediate

a. fast

The ability of muscle cells to respond to nerve stimuli is called: a. irritability. b. contractility. c. extensibility. d. elasticity.

a. irritability.

Most body movements are _____ contractions. a. isotonic b. isometric c. a combination of isotonic and isometric d. single twitch

a. isotonic

Bundles of fine fibers that extend lengthwise along muscle fibers are called: a. myofibrils. b. myofilaments. c. striae. d. sarcoplasmic reticulum.

a. myofibrils.

Cross-bridges are also called: a. myosin heads. b. motor end plates. c. synapses. d. motor neurons.

a. myosin heads.

The plasma membrane of a muscle fiber is called the: a. sarcolemma. b. myofibril. c. sarcoplasm. d. sarcomere.

a. sarcolemma.

Skeletal muscles are innervated by: a. somatic motor neurons. b. autonomic motor neurons. c. both somatic and autonomic motor neurons. d. internal stimulation.

a. somatic motor neurons.

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.

a. the calcium ions are attached to the troponin.

The myofibrils contain about how many sarcomeres? a. 150,000 b. 15,000 c. 1500 d. 150

b. 15,000

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

b. A-bands

Which of the following is not one of the major functions of muscles? a. Movement b. Protection c. Heat production d. Posture

b. Protection

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.

b. Sarcocyte

Which type of muscle is responsible for peristalsis? a. Multiunit smooth b. Single-unit smooth c. Cardiac d. Striated

b. Single-unit smooth

_____ muscle is also known as striated muscle. a. Smooth b. Skeletal c. Involuntary d. Visceral

b. Skeletal

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

b. Smooth

Which of the following terms describes an isometric contraction? a. Eccentric contraction b. Static tension c. Concentric contraction d. Both A and C

b. Static tension

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.

b. actin.

A decrease in muscle size is termed: a. hyperplasia. b. atrophy. c. hypertrophy. d. treppe.

b. atrophy.

Painful muscle contractions or involuntary twitches are called: a. tetanic contractions. b. cramps. c. convulsions. d. fibrillations.

b. cramps.

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

b. isotonic

The lactate produced by anaerobic respiration is converted back to glucose in the: a. lungs. b. liver. c. mitochondria. d. sarcoplasmic reticulum.

b. liver.

The protein molecule that has heads jutting out for cross-bridging is: a. actin. b. myosin. c. troponin. d. tropomyosin.

b. myosin.

Muscles usually contract to about _____ of their length. a. 30% b. 40% c. 80% d. 90%

c. 80%

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.

c. Muscles with less than normal muscle tone are referred to as spastic.

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

c. Myofilament, myofibril, fiber

Which structure functions to temporarily store calcium ions? a. T-tubules b. Sarcolemma c. Sarcoplasmic reticulum d. Myofilaments

c. Sarcoplasmic reticulum

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.

c. The more muscle fibers stimulated by a motor neuron, the more precise the movements of that muscle can be.

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.

c. acetylcholine.

Endurance training is also known as: a. isometrics. b. hypertrophy. c. aerobic training. d. strength training.

c. aerobic training.

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.

c. after an injury to a muscle.

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.

c. allow for electrical signals to move deeper into the cell.

The characteristic of the muscle cell that directly causes movement is: a. excitability. b. irritability. c. contractility. d. extensibility.

c. contractility.

The substance that attracts oxygen in the myoglobin molecule is: a. hemoglobin. b. calcium. c. iron. d. ATP.

c. iron.

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.

c. movement is produced.

A motor unit is most correctly described as _____ and a motor neuron. a. sarcomere(s) b. myofibril(s) c. muscle fiber(s) d. filament(s)

c. muscle fiber(s)

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.

c. myosin.

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.

c. replenish energy supply.

The smallest contractile unit of muscle is a: a. fiber. b. myofibril. c. sarcomere. d. myofilament.

c. sarcomere.

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.

c. the sarcoplasmic reticulum begins actively pumping calcium back into its sacs.

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.

c. thin and thick filaments are aligned in sarcomeres like skeletal muscles.

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.

c. unique name for the plasma membrane of a muscle fiber.

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.

d. All of the above are correct.

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.

d. All of the above are correct.

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.

d. All of the above are end-products of the breakdown of ATP.

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.

d. All of the above statements are correct.

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

d. Isometric

Which of the following is not associated with the thin myofilament? a. Troponin b. Tropomyosin c. Actin d. Myosin

d. Myosin

Physiological muscle fatigue may be caused by: a. a relative lack of ATP. b. high levels of lactate. c. failure of the sodium-potassium pumps. d. all of the above.

d. all of the above.

The ion necessary for cross-bridging is: a. iron. b. sodium. c. potassium. d. calcium.

d. calcium.

Glucose can be stored in the muscle as: a. creatine phosphate. b. ATP. c. myoglobin. d. glycogen.

d. glycogen.

The motor end plate makes up part of the: a. Z-line. b. T-tubules. c. sarcoplasmic reticulum. d. neuromuscular junction.

d. neuromuscular junction.

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 lactate. d. produces the maximum amount of energy available from each glucose molecule.

d. produces the maximum amount of energy available from each glucose molecule.

In the structure called a triad, the T-tubule is sandwiched between: a. actin filaments. b. myofibrils. c. sarcolemmas. d. sacs of sarcoplasmic reticulum.

d. sacs of sarcoplasmic reticulum.

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.

d. skeletal muscles contract with varying degrees of strength at different times.

Treppe is also called: a. tetanus. b. electromyography. c. wave summation. d. staircase phenomenon.

d. staircase phenomenon.