MUSCLE SAMPLE QUESTIONS:

10. The region of the resting sarcomere where the thin and thick filaments are overlapping is seen in the _______________. A) narrow dark line known as the Z line B) dark color of the I bands C) lighter region of the I bands D) dark color of the A bands

D) dark color of the A bands Feedback: See Figure 12.6 The striations of skeletal muscles are produced by thick and thin filaments.

20. Dense bodies are characteristic of ______________. A) smooth muscle B) cardiac muscle C) skeletal muscle

A) smooth muscle Feedback: Dense bodies are cytoplasmic protein structures which are analogous to the Z discs of striated muscle. See Figure 12.35.

12. The basic unit of muscle contraction is the sarcomere, which is ______________. A) one A band and the adjacent I band B) the distance from one Z line to the next C) equivalent to a fascicle of muscle fibers D) equivalent to one of the myofibrils within a muscle fiber

B) the distance from one Z line to the next Feedback: See Figure 12.6 The striations of skeletal muscles are produced by thick and thin filaments.

23. According to the sliding filament mechanism of muscle contraction, sarcomeres shorten: A. following the bonding of calcium to myosin B. as actin slides over myosin C. as troponin slides over tropomyosin D. following the bonding of actin to Z lines

B. as actin slides over myosin

28. In an isotonic muscle twitch, the fibers develop: A. enough force (tension) to move tropomyosin away from actin B. enough force to overcome the load, then shorten C. force but do not shorten. D. not enough force to overcome the load.

C. force but do not shorten.

6. Skeletal muscle cells are striated, that is they have alternating dark and light bands called _____________, respectively. A) A and I bands B) H and M bands C) Z and M lines D) I and H bands

A) A and I bands Feedback: See Figure 12.6 The striations of skeletal muscles are produced by thick and thin filaments.

4. At what stage in the cross-bridge cycle is ATP split into ADP and Pi? A) Before the cross bridges of myosin can attach to actin. B) During the power stroke when the myosin cross bridge flexes. C) At the end of the power stroke before myosin lets go of the actin filament. D) At the end of the power stroke after myosin lets go.

A) Before the cross bridges of myosin can attach to actin. The myosin head has an actin binding site and an ATP binding site, which serves as an ATPase to hydrolyze ATP. When ATP is hydrolyzed into ADP and Pi, the myosin head becomes activated and changes its orientation and is ready to bind to the actin subunits. See Figure 12.10 Activation of the myosin head.

6. The ability of myosin to interact with actin is regulated by the binding of _________. A) Ca2+ to troponin B) ATP to actin C) Ca2+ to tropomyosin D) titin to ATP

A) Ca2+ to troponin Feedback: The binding of Ca2+ to troponin causes movement of the troponin-tropomyosin complex which exposes binding sites on the actin. See Figure 12.14 The role of Ca2+ in muscle contraction.

25. The cerebellum cannot excite skeletal muscle contraction. A) True B) False

A) True Feedback: All output from the cerebellum is inhibitory.

16. Small motor units having a small innervation ratio allow for greater control than large motor units. A) True B) False

A) True Feedback: In the extraocular muscles that position the eyes, the innervation ratio is 1:23 which affords a finer degree of control than the gastrocnemius muscle that has an innervation ration of 1:1,000 which results in powerful contractions.

23. Alpha motoneurons are lower motoneurons that exit the spinal cord by way of the ventral root of a spinal nerve. A) True B) False

A) True Feedback: See Figure 12.28 The knee-jerk reflex.

18. Strabismus can be corrected by injecting Botox into the affected extraocular muscle. A) True B) False

A) True Feedback: Strabismus is deviation of the eye and by paralyzing the affected extraocular muscle, corrects the condition. 19 CORRECT

19. Lower motor neurons are influenced by effects from the upper motor neurons as well as from sensory feedback from the muscles and tendons. A) True B) False

A) True Feedback: Voluntary control of skeletal muscles is due to the influence of upper motor neurons and reflex activity that arises from sensory feedback.

3. During contraction the ________________. A) actin filaments bind to the myosin cross bridges B) I bands lengthen C) sarcomeres do not change in length D) size of the H zone increases

A) actin filaments bind to the myosin cross bridges Feedback: During contraction the I bands become shorter, the sarcomeres become shorter, and the size of the H zone decreases. See Figure12.9 The sliding filament model of muscle contraction and Table 12.2 Summary of the Sliding Filament Theory of Contraction.

2. Abductor and adductor muscles make up pairs that together are called __________. A) antagonistic B) agonistic C) complementary D) permissive

A) antagonistic Feedback: Abductor and adductor muscles act on the same joint to produce opposite actions, termed antagonistic.

7. If enough muscle fibers contract to make the muscle as a whole shorten in length, the muscle is said to exhibit ________________ contractions. A) concentric B) eccentric C) isometric

A) concentric Feedback: Isometric contractions exhibit an increase in tension within the muscle without shortening. In an eccentric contraction, the muscle will lengthen despite its contraction.

19. The Ca2+ that is required for sustained contraction of smooth muscle fibers comes mainly from the __________________. A) extracellular fluid surrounding the fibers B) cisternae of the rough endoplasmic reticulum C) varicosities of autonomic nerve fibers D) sarcoplasmic reticulum

A) extracellular fluid surrounding the fibers Feedback: The sarcoplasmic reticulum is less developed in smooth muscle therefore Ca2+ released from this organelle may account for only the initial phase of the contraction. Extracellular Ca2+ diffusion into the smooth muscle cell is responsible for sustained contractions.

14. Excitation-contraction coupling refers especially to the ________________. A) means by which electrical excitation of a muscle results in muscle contraction B) propagation of action potentials from the neuromuscular junction to the T tubules C) calcium release and binding to troponin molecules D) attachment of myosin cross bridges to the thin filaments

A) means by which electrical excitation of a muscle results in muscle contraction Feedback: The coupling is achieved by calcium which enters the muscle cell cytoplasm in response to electrical excitation and which stimulates the events culminating in contraction. See Figure 12.16 The structures involved in excitation-contraction coupling.

25. Medications (drugs) that inhibit __________ would result in an increase in the force of muscle contraction associated with a single twitch. A. acetylcholinesterase B. calcium channels on somatic motor neurons C. acetylcholine receptors D. calcium receptors on troponin

A. acetylcholinesterase

21. Which of the following pairs are both contractile proteins in skeletal muscle? A. actin and myosin B. actin and troponin C. myosin and tropomyosin D. troponin and tropomyosin

A. actin and myosin

15 If a muscle is repeatedly stimulated and allowed to relax between stimuli, the successive contractions will be stronger. This phenomenon, known as treppe, or staircase effect, is thought to be due to the accumulation of neurotransmitter in the neuromuscular cleft. A) True B) False

B) False Feedback: It is thought to be due to an increase in intracellular Ca2+.

20. Damage to higher motor neurons immediately leads to spastic paralysis, in which the muscles are overly sensitive to stretch and exhibit exaggerated contractions. A) True B) False

B) False Feedback: Damage to upper motor neurons at first produces spinal shock in which there is flaccid paralysis. This is followed in a few weeks by spastic paralysis.

17. To achieve coordinated muscle contraction, it is important that all the myosin cross bridges bind to the thin filaments and produce their power strokes in unison. A) True B) False

B) False Feedback: During a normal contraction, only a portion of the cross bridges are attached at any given time. The power strokes are thus not in synchrony but rather like the actions of a team engaged in a tug of war where the pulling action is asynchronous.

21. Impulses from one motor nerve fiber will cause the contraction of one muscle fiber. A) True B) False

B) False Feedback: Each somatic motor neuron innervates a group of skeletal muscle fibers making up what is known as a motor unit. See Figure 12.4 Motor units.

24. Skeletal muscles are called voluntary because they only contract in response to conscious, voluntary control from the brain. A) True B) False

B) False Feedback: Skeletal muscles are often called voluntary but they also contract in an unconscious reflex fashion in response to a particular stimulus.

15. The nervous system must monitor the behavior of muscles. The receptor that provides information about the amount of tension being exerted on a given tendon is the ________. A) extrafusal fiber B) Golgi tendon organ C) gamma motoneuron D) muscle spindle

B) Golgi tendon organ Feedback: Muscle spindles are receptors that monitor muscle length and extrafusal fibers are part of the muscle spindle apparatus. Gamma motoneurons are lower motor neurons that innervate the intrafusal fibers of a muscle spindle.

17. Slow twitch muscle fibers _________________. A) have a relatively low oxidative capacity B) are very resistant to fatigue C) have a high glycogen content D) have a high myosin ATPase content

B) are very resistant to fatigue Feedback: Slow twitch muscle fibers have a high oxidative capacity, have a low glycogen content, and have a low myosin ATPase content. See Table 12.3 Characteristics of Muscle Fiber Types.

8.A motor unit is __________. A) the motor end plate where a nerve fiber synapses with a muscle fiber B) one motor neuron and all muscle fibers that it innervates C) a spinal reflex arc D) a sarcomere

B) one motor neuron and all muscle fibers that it innervates Feedback: See Figure 12.4 Motor units.

16. Sustained muscle activity may consume ATP faster than aerobic respiration can produce it. In such circumstances, ATP can be made by combining ADP with phosphate groups borrowed from ________________. A) creatine kinase B) phosphocreatine C) cyclic AMP D) phospholipids

B) phosphocreatine Feedback: Within muscle cells, the phosphocreatine concentration is more than three times the concentration of ATP and represents a ready reserve of high energy phosphate than can be donated directly to ADP. See Figure 12.24 The production and utilization of phosphocreatine in muscles.

31. Increasing the afterload on a muscle will: A. cause greater amounts of calcium to be released during a twitch B. decrease the velocity with which the muscle shortens C. decrease the duration of the isometric phase of a twitch D. increase the duration of the isotonic phase of a twitch

B. decrease the velocity with which the muscle shortens

29. Compared to slow-oxidative (red) muscle, fast-glycolytic (white) muscle fibers have more: A. blood capillaries B. glycogen C. myoglobin D. mitochondria

B. glycogen

32. Compared to slow-oxidative (red) muscle, fast-glycolytic (white) muscle fibers have more: A. blood capillaries B. glycogen C. myoglobin D. mitochondria

B. glycogen

27. As you are sitting here taking this exam, the postural control muscles that are keeping you upright are contracting: A. at a tetanic frequency B. isometrically C. isotonically D. with the maximum number of motor units available

B. isometrically

9. Terminal cisternae of the sarcoplasmic reticulum release Ca2+ when signaled by the ________________. A) motor end plate B) sarcomeres C) T tubules D) motor nerve fibers

C) T tubules Feedback: Once the motor nerve fiber has reached the neuromuscular junction and has been tranmitted to the muscle cell, the spread of the action potential into the T tubules stimulates the opening of their voltage gated Ca2+ channels which in turn stimulates the opening of the voltage gated Ca2+channels in the terminal cisternae of the sarcoplasmic reticulum. See Figure 12.16 Excitation-contraction coupling in skeletal muscle.

1 Suppose you are sitting in the middle of a sofa and move both of your hands to your stomach. This action of the arms is known as ________________. A) extension B) abduction C) adduction D) flexion

C) adduction Feedback: Adduction is a movement toward the midline of the body whereas abduction is a movement away from the midline of the body. Extension is a movement that increases the angle at a joint whereas flexion is a movement that decreases the angle at a joint. See Table 12.1 Skeletal Muscle Actions.

3. The fibrous connective tissue sheath, which encloses a whole muscle, is called the _______________. A) endomysium B) perimysium C) epimysium D) sarcolemma

C) epimysium Feedback: The perimysium is the fibrous connective tissue that surrounds fascicles within the muscle, the endomysium surrounds individual muscle fibers, and the sarcolemma is the plasma membrane of a single muscle fiber. See Figure 12.1 The structure of a skeletal muscle .

11. The sensitivity of muscle spindles to stretch can be adjusted by _________________. A) further stretching of the extrafusal fibers B) alpha motoneurons C) gamma motoneurons D) annulospiral nerve endings

C) gamma motoneurons Feedback: The effect of gamma motoneurons, which is sometimes termed active stretch of the spindles, serves to increase the sensitivity of the spindles when the entire muscle is passively stretched by external forces.

5. Skeletal muscle cells are different from other cells in that they _____________. A) lack smooth endoplasmic reticulum B) have no mitochondria C) have multiple nuclei D) depend entirely on anaerobic respiration

C) have multiple nuclei Feedback: Skeletal muscle cells have the same organelles that are present in other cells but unlike other cells, they have multiple nuclei because each muscle fiber is formed from the union of several embryonic myoblasts and their nuclei are retained in the resulting muscle fiber. See Figure 12.2 The appearance of skeletal muscle fibers through the light microscope.

13 A person continues breathing heavily for some time after exercising in order to "repay an oxygen debt". This oxygen debt includes all of the following except the oxygen that was __________________. A) taken from hemoglobin in the blood B) taken from myoglobin in the muscle C) needed to replenish the store of glycogen in the muscle D) needed to metabolize the lactic acid produced by exercise

C) needed to replenish the store of glycogen in the muscle Feedback: This occurs during recovery after the exercise, which is accomplished by the Cori cycle.

18. Which of the following is not a factor in muscle fatigue? A) a drop in intracellular pH B) accumulation of lactic acid C) production of IPSPs by motor neurons D) accumulation of extracellular K+

C) production of IPSPs by motor neurons Feedback: The production of IPSPs occurs in higher brain centers to regulate muscle activity.

10. As opposed to the upper motor neurons, the lower motor neurons have their cell bodies located in the ________________. A) thalamus as opposed to the cerebral cortex B) medulla oblongata as opposed to higher brain centers C) spinal cord as opposed to the brain D) lumbar and sacral regions as opposed to cervical and thoracic

C) spinal cord as opposed to the brain Feedback: The axons of these neurons are within nerves that stimulate muscle contraction. See Table 12.5 A Partial Listing of Terms Used to Describe the Neural Control of Skeletal Muscles.

2. A muscle is stimulated and exhibits a contraction (twitch). Before this twitch is over, it is stimulated again, and a second twitch occurs "piggyback" on the first one and causes a higher contraction strength. This phenomenon is called ______________. A) incomplete tetanus B) graded contraction C) summation D) complete tetanus

C) summation Feedback: Incomplete tetanus occurs by increasing the stimulation frequency to a muscle resulting in the relaxation time becoming shorter and shorter between twitches. Complete tetanus occurs by increasing the stimulation frequency even more so that a smooth sustained contraction is observed. Graded contractions refers to contractions of different strengths. See Figure 12.19 Incomplete and complete tetanus.

7. If a muscle is already at about 80% of its resting length, it cannot be stimulated to contract any more because ____________. A) there is no more ATP B) the myosin cross bridges cannot reach the actin filaments C) the Z lines abut against the thick filaments and cannot go any further D) muscle fibers obey the all-or-none law

C) the Z lines abut against the thick filaments and cannot go any further Feedback: See Figure 12.21 The length-tension relationship in skeletal muscles.

5. Rigor mortis in a corpse results from the fact that ____________. A) all of the neurotransmitter is used up B) all of the calcium ions are used up C) thick filaments cannot let go of the thin filaments without ATP D) motor neurons can no longer function

C) thick filaments cannot let go of the thin filaments without ATP Feedback: In nonliving muscle, without ATP the ADP remains bound to the cross bridges and the cross bridges remain tightly bound to actin. Muscles will remain in a partially contracted state until decomposition ensues.

9. Contraction in a muscle occurs because the ______________. A) thin filaments get shorter B) thick filaments get shorter C) thin filaments slide between the thick filaments D) titin proteins pull on opposite ends of the sarcomere

C) thin filaments slide between the thick filaments Feedback: As the filaments slide (but not shorten), the sarcomeres become shorter. The titin proteins have elastic properties that contribute to relaxation. See Figure 12.9 The sliding filament model of muscle contraction.

22. A motor unit is defined as the number of: A. sarcomeres in a muscle cell B. muscle cells in a whole muscle C. muscle cells innervated by a motor neuron D. motor neurons innervating a whole muscle

C. muscle cells innervated by a motor neuron

24. The neuromuscular junction is an area on the plasma membrane of a muscle cell where: A. T-tubules connect to the sarcoplasmic reticulum B. sarcomeres attach to acetylcholine receptors C. somatic motor neurons release acetylcholine D. somatic motor neurons attach to sodium channels

C. somatic motor neurons release acetylcholine

12. The cerebral nuclei normally inhibit lower motor neurons. Therefore, damage to the cerebral nuclei can cause __________________. A) clonus B) paraplegia C) intention tremor D) chorea

D) chorea Feedback: Chorea is sudden and uncontrolled random movements and also akinesia which is lack of desire to use the affected limb result from damage to the cerebral nuclei. See Table 12.7 Symptoms of Upper Motor Neuron Damage

4. Within a muscle, the fibers are divided into larger bundles called _____, each surrounded by its own connective tissue sheath. A) sarcomeres B) sarcolemma C) myofibers D) fascicles

D) fascicles Feedback: Myofibers are another name for muscle fiber, sarcolemma is the plasma membrane of a single muscle fiber, and a sarcomere is the basic unit of striated muscle.

14. Myosin light-chain kinase __________________. A) is activated by cAMP B) phosphorylates myosin to regulate muscle contraction in cardiac muscle C) phosphorylates myosin to stimulate relaxation in smooth muscle D) is antagonized by the actions of myosin phosphatase

D) is antagonized by the actions of myosin phosphatase Feedback: Myosin light-chain kinase activates cross bridges and contraction occurs whereas myosin phosphatase inactivates cross bridges and relaxation occurs. See Figure 12.37 Excitation-contraction coupling in smooth muscle.

11. The thick filaments of muscle fibers are composed of ______________. A) tropomyosin B) troponin C) actin D) myosin

D) myosin Feedback: Troponin, tropomyosin, and actin make up the thin filaments of muscle fibers.

1. When a skeletal muscle contracts, it usually moves the bone at one end much more than the bone at its other end. The attachment of the muscle to the less moveable bone is called its ______________. A) ligament B) insertion C) flexor D) origin

D) origin Feedback: The insertion is the more moveable bony attachment of the muscle. A flexor is a skeletal muscle action that decreases the angle at a joint. A ligament is a band of dense regular connective tissue that connects bones to cartilage and serves to strengthen joints.

8. ATP is required by two different processes that are necessary for the contraction and relaxation of a muscle. One is the interaction between thick and thin filaments of the sarcomeres and the other is the ___________________. A) binding of acetylcholine to the motor end plate B) release of calcium from the sarcoplasmic reticulum C) movement of the troponin-tropomyosin complex D) reuptake of calcium by the sarcoplasmic reticulum.

D) reuptake of calcium by the sarcoplasmic reticulum. Feedback: The reuptake of calcium by the sarcoplasmic reticulum requires active transport pumps, which require ATP to operate.

13. The Ca2+ that binds to troponin to activate muscle contraction comes from the storage sites located in the ________________. A) transverse tubules B) extracellular fluid C) synaptic vesicles of the motor neuron D) sarcoplasmic reticulum

D) sarcoplasmic reticulum Feedback: The sarcoplasmic reticulum is a modified endoplasmic reticulum consisting of interconnected sacs and tubes that surround each myofibril within the muscle fiber. See Figure 12.15 The sarcoplasmic reticulum.

26. Action potentials on the T-tubules of skeletal muscle cells: A. activate calcium pumps within the cytoplasm of a cell B. cause tropomyosin to change shape C. activate myosin receptors on actin D. cause the release of calcium from the sarcoplasmic reticulum

D. cause the release of calcium from the sarcoplasmic reticulum

29. In an isotonic muscle twitch, the fibers develop: A. enough force (tension) to move tropomyosin away from actin B. enough force to overcome the preload, then shorten C. force but do not shorten D. enough force to overcome the afterload, then shorten

D. enough force to overcome the afterload, then shorten

30. Slightly stretching a muscle before initiating contraction will enable the muscle to generate more force because: A. tropomyosin more easily pulls away from actin B. the activity of the calcium pump is increased C. greater amounts of calcium are released during a twitch D. there is a more optimal alignment of actin-myosin binding sites

D. there is a more optimal alignment of actin-myosin binding sites

22. A muscle contracts more strongly when lifting a 20-pound weight than when lifting a 5-pound weight. This is because more fibers are contracting, not because individual fibers contract harder. A) True B) False

Feedback: When contractions of greater strength are required, more and more motor units are activated in a process called recruitment. A) True

20. The muscles of a professional sprinter are most likely to have ________. a. 80 percent fast-twitch muscle fibers percent slow-twitch muscle fibers b. 20 percent fast-twitch muscle fibers percent slow-twitch muscle fibers c. 50 percent fast-twitch muscle fibers percent slow-twitch muscle fibers d. 40 percent fast-twitch muscle fibers percent slow-twitch muscle fibers

a. 80 percent fast-twitch muscle fibers percent slow-twitch muscle fibers

23. Which of the following statements is false? a. Slow fibers have a small network of capillaries. b. Slow fibers contain the pigment myoglobin. c. Slow fibers contain a large number of mitochondria. d. Slow fibers contract for extended periods.

a. Slow fibers have a small network of capillaries. b. Slow fibers contain the pigment myoglobin.

27. Which of the following statements describes smooth muscle cells? a. They are resistant to fatigue. b. They have a rapid onset of contractions. c. They cannot exhibit tetanus. d. They primarily use anaerobic metabolism.

a. They are resistant to fatigue.

17. A sprinter would experience muscle fatigue sooner than a marathon runner due to ________. a. anaerobic metabolism in sprinter b. anaerobic metabolism in marathon runner the muscles of the c. aerobic metabolism in the muscles of the sprinter d. glycolysis in the muscles of the marathon runner

a. anaerobic metabolism in sprinter

26. Smooth muscles differ from skeletal and cardiac muscles in that they ________. a. lack myofibrils b. are under voluntary control c. lack myosin d. lack actin

a. lack myofibrils

8. Depolarization of the sarcolemma means ________. a. the inside of the membrane has become less negative as sodium ions accumulate b. the outside of the membrane has become less negative as sodium ions accumulate c. the inside of the membrane has become more negative as sodium ions accumulate d. the sarcolemma has completely lost any electrical charge

a. the inside of the membrane has become less negative as sodium ions accumulate

21. The muscles of a professional marathon runner are most likely to have ________. a. 80 percent fast-twitch muscle fibers percent slow-twitch muscle fibers b. 20 percent fast-twitch muscle fibers percent slow-twitch muscle fibers c. 50 percent fast-twitch muscle fibers percent slow-twitch muscle fibers d. 40 percent fast-twitch muscle fibers percent slow-twitch muscle fibers

b. 20 percent fast-twitch muscle fibers percent slow-twitch muscle fibers

5. Which element is important in directly triggering contraction? a. sodium (Na+) b. calcium (Ca++) c. potassium (K+) d. chloride (Cl )

b. calcium (Ca++)

16. Muscle fatigue is caused by ________. a. buildup of ATP and lactic acid levels b. exhaustion of energy reserves and buildup of lactic acid levels c. buildup of ATP and pyruvic acid levels d. exhaustion of energy reserves and buildup of pyruvic acid levels

b. exhaustion of energy reserves and buildup of lactic acid levels

7. The correct order for the smallest to the largest unit of organization in muscle tissue is ________. a. fascicle, filament, muscle fiber, myofibril b. filament, myofibril, muscle fiber, fascicle c. muscle fiber, fascicle, filament, myofibril d. myofibril, muscle fiber, filament, fascicle

b. filament, myofibril, muscle fiber, fascicle

18. What aspect of creatine phosphate allows it to supply energy to muscles? a. ATPase activity b. phosphate bonds c. carbon bonds d. hydrogen bonds

b. phosphate bonds

11. The cell membrane of a muscle fiber is called ________. a. myofibril b. sarcolemma c. sarcoplasm d. myofilament

b. sarcolemma

22. Which of the following statements is true? a. Fast fibers have a small diameter. b. Fast fibers contain loosely packed myofibrils. c. Fast fibers have large glycogen reserves. d. Fast fibers have many mitochondria.

c. Fast fibers have large glycogen reserves.

6. Which of the following properties is not common to all three muscle tissues? a. excitability b. the need for ATP c. at rest, uses shielding proteins to cover actin- binding sites d. elasticity

c. at rest, uses shielding proteins to cover actin- binding sites

12. Muscle relaxation occurs when ________. a. calcium ions are actively transported out of the sarcoplasmic reticulum b. calcium ions diffuse out of the sarcoplasmic reticulum c. calcium ions are actively transported into the sarcoplasmic reticulum d. calcium ions diffuse into the sarcoplasmic reticulum

c. calcium ions are actively transported into the sarcoplasmic reticulum

13. During muscle contraction, the cross-bridge detaches when ________. a. the myosin head binds to an ADP molecule b. the myosin head binds to an ATP molecule c. calcium ions bind to troponin d. calcium ions bind to actin

c. calcium ions bind to troponin

15. During which phase of a twitch in a muscle fiber is tension the greatest? a. resting phase b. repolarization phase c. contraction phase d. relaxation phase

c. contraction phase

28. From which embryonic cell type does muscle tissue develop? a. ganglion cells b. myotube cells c. myoblast cells d. satellite cells

c. myoblast cells

25. If cardiac muscle cells were prevented from undergoing aerobic metabolism, they ultimately would ________. a. undergo glycolysis b. synthesize ATP c. stop contracting d. start contracting

c. stop contracting

10. According to the sliding filament model, binding sites on actin open when ________. a. creatine phosphate levels rise b. ATP levels rise c. acetylcholine levels rise d. calcium ion levels rise

d. calcium ion levels rise

24. Cardiac muscles differ from skeletal muscles in that they ________. a. are striated b. utilize aerobic metabolism c. contain myofibrils d. contain intercalated discs

d. contain intercalated discs

19. Drug X blocks ATP regeneration from ADP and phosphate. How will muscle cells respond to this drug? a. by absorbing ATP from the bloodstream b. by using ADP as an energy source c. by using glycogen as an energy source d. none of the above

d. none of the above

14. Thin and thick filaments are organized into functional units called ________. a. myofibrils b. myofilaments c. T-tubules d. sarcomeres

d. sarcomeres

29. Which cell type helps to repair injured muscle fibers? a. ganglion cells b. myotube cells c. myoblast cells d. satellite cells

d. satellite cells

4. Muscle that has a striped appearance is described as being ________. a. elastic b. nonstriated c. excitable d. striated

d. striated

9. In relaxed muscle, the myosin-binding site on actin is blocked by ________. a. titin b. troponin c. myoglobin d. tropomyosin

d. tropomyosin