chapter 9

1. What is the role of tropomyosin in skeletal muscles? A. Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules. B. Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules. C. Tropomyosin is the chemical that activates the myosin heads. D. Tropomyosin is the receptor for the motor neuron neurotransmitter.

A

3. Most skeletal muscles contain ________. A. a mixture of fiber types B. muscle fibers of the same type C. a predominance of slow oxidative fibers D. a predominance of fast oxidative fibers

A

Smooth muscle is characterized by all of the following except ________. A. there are more thick filaments than thin filaments B. there are noncontractile intermediate filaments that attach to dense bodies within the cell C. there are no sarcomeres D. it appears to lack troponin

A

The giant protein titin maintains the organization of the ________ assisting in muscle stretching. A. A band B. M line C. I band D. Z disc

A

2. Which muscle cells have the greatest ability to regenerate? A. no muscle can regenerate B. smooth C. skeletal D. cardiac

B

5. The strongest muscle contractions are normally achieved by ________. A. recruiting small and medium muscle fibers B. increasing the stimulation up to the maximal stimulus C. increasing stimulus above the treppe stimulus D. increasing stimulus above the threshold

B

Muscle tissue has all of the following properties except ________. A. contractility B. excitability C. secretion D. extensibility

C

Muscle tone is ________. A. the feeling of well-being following exercise B. the condition of athletes after intensive training C. a state of sustained partial contraction D. the ability of a muscle to efficiently cause skeletal movements

C

. Rigor mortis occurs because ________. A. no ATP is available to release attached actin and myosin molecules B. the cells are dead C. sodium ions leak into the muscle causing continued contractions D. proteins are beginning to break down, thus preventing a flow of calcium ions

a

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________. A. no muscle tension could be generated B. cross bridge attachment would be optimum because of all the free binding sites on actin C. maximum force production would result because the muscle has a maximum range of travel D. ATP consumption would increase because the sarcomere is "trying" to contract

a

Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions? A. multiunit smooth muscle B. visceral smooth muscle C. cardiac muscle D. skeletal muscle

a

Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers? A. a long, relaxing swim B. a sprint by an Olympic runner C. playing baseball or basketball D. gym climbing

a

What is the functional unit of a skeletal muscle called? A. a sarcomere B. a myofibril C. a myofilament D. the sarcoplasmic reticulum

a

What is the most distinguishing characteristic of muscle tissue? A. the ability to transform chemical energy into mechanical energy B. the diversity of activity of muscle tissue C. the design of the fibers D. the ability to respond to nervous stimulation

a

Which of the choices below does not describe how excess postexercise oxygen consumption (oxygen deficit) restores metabolic conditions? A. increases the level of lactic acid in the muscle B. converts lactic acid back into glycogen stores in the liver C. replaces the oxygen removed from myoglobin D. resynthesizes creatine phosphate and ATP in muscle fibers

a

Which of the following is the correct sequence of events for muscle contractions? A. motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments B. muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments C. neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke D. neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR,

a

27. Which of the following is not a component of the standard treatment for muscle strain? A. ice on the muscle B. stretching of the muscle C. elevation of the limb D. rest of the muscle

b

During muscle contraction, myosin cross bridges attach to which active sites? A. thick filaments B. actin filaments C. myosin filaments D. Z discs

b

Excitation-contraction coupling requires which of the following substances? A. ATP and glucose B. Ca2+ and ATP C. ATP only D. Ca2+ only

b

Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptors.

b

Myoglobin ________. A. is a protein involved in the direct phosphorylation of ADP B. stores oxygen in muscle cells C. breaks down glycogen D. produces the end plate potential

b

The major function of the sarcoplasmic reticulum in muscle contraction is to ________. A. synthesize actin and myosin myofilaments B. regulate intracellular calcium concentration C. make and store phosphocreatine D. provide a source of myosin for the contraction process

b

The oxygen-binding protein found in muscle cells is ________. A. hemoglobin B. myoglobin C. immunoglobin D. ATP

b

What part of the sarcolemma contains acetylcholine receptors? A. any part of the sarcolemma B. motor end plate C. end of the muscle fiber D. part adjacent to another muscle cell

b

What structure in skeletal muscle cells functions in calcium storage? A. mitochondria B. sarcoplasmic reticulum C. myofibrillar network D. intermediate filament network

b

Which of the following describes the cells of unitary smooth muscle? A. They consist of muscle fibers that are structurally independent of each other. B. They exhibit spontaneous action potentials. C. They depend upon recruitment using the autonomic nervous system. D. They are used for vision and hair raising.

b

Which of the following is not a role of ionic calcium in muscle contraction? A. triggers neurotransmitter secretion B. activates epinephrine released from adrenal gland C. binds with troponin D. removes contraction inhibitor

b

Which of the following statements is false or incorrect? A. Under normal resting conditions, cardiac muscle tissue contracts and relaxes about 75 times per minute. B. Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP. C. Cardiac muscle fibers can use lactic acid to make ATP. D. Cardiac muscle contracts when stimulated by its own autorhythmic muscle cells.

b

Which of the following statements is true? A. Cardiac muscle cells are found in the heart and large blood vessels. B. Striated muscle cells are long and cylindrical with many nuclei. C. Cardiac muscle cells have many nuclei. D. Smooth muscle cells have T tubules.

b

Which of the following surrounds the individual muscle cell? A. fascicle B. endomysium C. epimysium D. perimysium

b

. During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________. A. a strong base B. stearic acid C. lactic acid D. hydrochloric acid

c

4. Fatigued muscle cells that recover rapidly are the products of ________. A. intense exercise of long duration B. slow exercise of long duration C. intense exercise of short duration D. slow exercise of short duration

c

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction? A. the tropomyosin blocking the myosin once full contraction is achieved B. calcium ions returning to the terminal cisternae C. acetylcholinesterase destroying the ACh D. the action potential stops going down the overloaded T tubules

c

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________. A. hydrolysis B. the electron transport chain C. glycolysis D. the citric acid cycle

c

Creatine phosphate functions in the muscle cell by ________. A. inducing a conformational change in the myofilaments B. forming a temporary chemical compound with myosin C. storing energy that will be transferred to ADP to resynthesize ATP D. forming a chemical compound with actin

c

In an isotonic contraction, the muscle ________. A. never converts pyruvate to lactate B. rapidly resynthesizes creatine phosphate and ATP C. changes in length and moves the "load" D. does not change in length but increases tension

c

The contractile units of skeletal muscles are ________. A. microtubules B. T tubules C. myofibrils D. mitochondria

c

The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________. A. ATP energizes the sliding process B. actin and myosin interact by the sliding filament mechanism C. the site of calcium regulation differs D. the trigger for contraction is a rise in intracellular calcium

c

What does excess postexercise oxygen consumption represent? A. the amount of oxygen equal to the oxygen already used B. the amount of oxygen taken into the body immediately after the exertion C. the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used D. amount of oxygen needed for aerobic activity to accomplish the same amount of work

c

What produces the striations of a skeletal muscle cell? A. the T tubules B. the sarcoplasmic reticulum C. the arrangement of myofilaments D. a difference in the thickness of the sarcolemma

c

Which of the following is true about smooth muscle? A. Smooth muscle cannot stretch as much as skeletal muscle. B. Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements. C. Certain smooth muscle cells can actually divide to increase their numbers. D. Smooth muscle has well-developed T tubules at the site of invagination.

c

Which of the following statements is most accurate? A. The I band lengthens during isotonic contraction. B. Myofilaments slide during isometric contractions. C. Muscle tension remains relatively constant during isotonic contraction. D. T tubules may be sliding during isotonic contraction.

c

Which of the following would be recruited later in muscle stimulation when contractile strength increases? A. many small motor units with the ability to stimulate other motor units B. large motor units with small, highly excitable neurons C. motor units with larger, less excitable neurons D. motor units with the longest muscle fibers

c

Once a motor neuron has fired, all the muscle fibers in a muscle contract.

false

. The muscle cell membrane is called the ________. A. epimysium B. endomysium C. perimysium D. sarcolemma

d

28. Which of the following is not a connective tissue sheath that wraps individual muscle fibers? A. epimysium B. endomysium C. perimysium D. aponeurosis

d

The sliding filament model of contraction involves ________. A. actin and myosin lengthening in order to slide past each other B. the Z discs sliding over the myofilaments C. the shortening of thick filaments so that thin filaments slide past D. actin and myosin sliding past each other and partially overlapping

d

The term aponeurosis refers to ________. A. the tropomyosin-troponin complex B. the rough endoplasmic reticulum C. the bands of myofibrils D. a sheetlike indirect attachment to a skeletal element

d

What is the functional role of the T tubules? A. hold cross bridges in place in a resting muscle B. stabilize the G and F actin C. synthesize ATP to provide energy for muscle contraction D. enhance cellular communication during muscle contraction

d

What is the primary function of wave summation? A. increase muscle tension B. prevent muscle fatigue C. prevent muscle relaxation D. produce smooth, continuous muscle contraction

d

What is the role of calcium ions in muscle contraction? A. increase levels of myoglobin B. reestablish glycogen stores C. form hydroxyapatite crystals D. bind to regulatory sites on troponin to remove contraction inhibition

d

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods? A. fatigue period B. relaxation period C. latent period D. refractory period

d

Which of the following is a factor that affects the velocity and duration of muscle contraction?

d

A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.

false

During isometric contraction, the energy used appears as movement.

false

Muscle contraction will always promote movement of body parts regardless of how they are attached.

false

. A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.

true

. Cardiac muscle has a limited regenerative capacity.

true

A contraction in which the muscle does not shorten but its tension increases is called isometric contraction.

true

Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments.

true

An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops.

true

Cells of unitary smooth muscle are found in the longitudinal and circular muscle layers of the intestine.

true

Eccentric contractions are more forceful than concentric contractions

true

Muscle cells store more creatine phosphate than ATP resulting in the muscle having a reserve source of energy.

true

Muscle tone is the small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units.

true

One of the functions of skeletal muscle contraction is production of heat.

true

Peristalsis is characteristic of smooth muscle.

true

Smooth muscles relax when intracellular Ca2+ levels drop but may not cease contractions.

true

The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily.

true

The force of muscle contraction is controlled by multiple motor unit summation or recruitment.

true

The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment.

true

When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands do not diminish in length.

true