Chapter 9- Skeletal Muscle Tissue

28) Identify the structure where ATP is produced. A) 6 B) 7 C) 1 D) 3 E) 2 ** look at doc

C) 1

29) Where is ATP is consumed? A) 1 B) 2 C) 3 D) 7 E) 8 ** look at doc

C) 3

20) The area in the center of the A band that contains no thin filaments is the A) Z line. B) M line. C) H band. D) I band. E) zone of overlap.

C) H band.

7) The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n) A) fascicle. B) tendon. C) ligament. D) epimysium. E) myofibril.

B) tendon.

76) Calcium ions are bound to troponin during which of the following steps. A) latent period B) contraction phase C) recovery phase D) the first 2 msec following stimulation E) None of the answers is correct.

B) contraction phase

3) Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for A) conduction. B) contraction. C) peristalsis. D) cushioning. E) None of the answers is correct.

B) contraction.

93) Which of the following is not true of the muscular system? A) It depends upon calcium stored and released from the skeletal system. B) It depends upon calcitonin and parathyroid hormone levels to maintain calcium homeostasis. C) It depends upon the integumentary system to protect muscles. D) It depends upon the cardiovascular system to provide the hemoglobin stored in slow muscle fibers. E) It depends upon the nervous system to stimulate skeletal muscle tissue to contract.

D) It depends upon the cardiovascular system to provide the hemoglobin stored in slow muscle fibers.

64) How would a drug that blocks acetylcholine receptors at the motor end plate affect skeletal muscle? A) It would make the muscles more excitable. B) It would produce uncontrolled muscle spasms. C) It would cause spastic paralysis (muscles are contracted and unable to relax). D) It would cause flaccid paralysis (muscles are relaxed and unable to contract). E) It would have little effect on skeletal muscles.

D) It would cause flaccid paralysis (muscles are relaxed and unable to contract).

26) Where would calcium ions be predominately found? A) 1 B) 2 C) 4 D) 8 E) 9 ** look at doc

E) 9

47) Which of the following is an ion that is more concentrated inside the cell than outside? A) sodium B) chloride C) hydrogen D) calcium E) potassium

E) potassium

63) Triggering of the muscle action potential occurs after A) acetylcholine binds to chemically gated channels in the motor end plate membrane. B) acetylcholinesterase binds to receptors on the end plate. C) calcium ion binds to channels on the end plate. D) the nerve action potential jumps across the neuromuscular junction. E) Any of these actions can produce an action potential in the muscle cell.

A) acetylcholine binds to chemically gated channels in the motor end plate membrane.

89) What is the contraction in graph (d) called? A) complete tetanus B) incomplete tetanus C) twitch D) wave summation E) treppe ** look at doc

A) complete tetanus

12) Individual muscle cells are surrounded by what connective tissue? A) endomysium B) perimysium C) sarcolemma D) sarcomere E) myofibrils

A) endomysium

6) The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the A) endomysium. B) perimysium. C) epimysium. D) superficial fascia. E) periosteum.

A) endomysium.

79) A muscle producing tension that peaks but falls to only intermediate stimulus rates is said to be in A) incomplete tetanus. B) complete tetanus. C) treppe. D) wave summation. E) recruitment.

A) incomplete tetanus.

24) Identify the structures labeled "1." A) mitochondria B) glycogen C) ATP D) myofibril E) synaptic vesicle ** look at doc

A) mitochondria

62) When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes A) more permeable to sodium ions. B) less permeable to sodium ions. C) more permeable to calcium ions. D) less permeable to potassium ions. E) repolarized.

A) more permeable to sodium ions.

92) In an isotonic contraction, A) muscle tension exceeds the load and the muscle lifts the load. B) tension rises and falls but the muscle length is constant. C) the peak tension is less than the load. D) many twitches fuse into one. E) flexion is produced.

A) muscle tension exceeds the load and the muscle lifts the load.

51) If potassium channels were blocked, the ________ phase of the action potential would not occur normally. A) repolarization B) depolarization C) refractory D) threshold

A) repolarization

14) The plasma membrane of skeletal muscle is called the A) sarcolemma. B) sarcomere. C) sarcosome. D) sarcoplasmic reticulum. E) sarcoplasm.

A) sarcolemma.

36) Which of the following best describes the term titin? A) substance that accounts for elasticity of resting muscle B) repeating unit of striated myofibrils C) storage site for calcium ions D) where thin filaments are anchored E) largely made of myosin molecules

A) substance that accounts for elasticity of resting muscle

11) At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a A) tendon. B) satellite cell. C) ligament. D) tenosynovium. E) sheath.

A) tendon.

159) List the interrelated steps that occur once the contraction cycle begins.

1: Exposure of active sites: calcium ions entering the sarcoplasm bind to troponin. 2: Formation of Cross-Bridges: when active sites are exposed, the energized myosin heads bind to them forming cross-bridges; 3: Pivoting of Myosin Heads: each myosin head points away from the M line. 4: Detachment of Cross-Bridges: Another ATP binds to the myosin head, the link between the active site on the actin molecule and the myosin head is broken. *5: Reactivation of Myosin: Myosin reactivation occurs when the free myosin head splits the ATP into ADP and a phosphate group. The energy released in this process is used to recock the myosin head

161) Why would a sprinter experience muscle fatigue before a marathon runner would?

A marathon runner builds up more slow fibers with slow oxidative (aerobic) fibers so they last the entire marathon (long period of time), while a sprinter builds up more fast fibers that are Fast glycolytic anaerobic fibers.

163) Six weeks after Fred broke his leg, the cast is removed. As he steps down from the exam table, his leg gives way, and he falls. Propose a logical explanation.

A muscle not regularly stimulated by a motor neuron will lose tone and mass and become weak (will atrophy). While his leg was immobilized, it did not receive sufficient stimulation to maintain proper tone. It will take a while for Bill's muscles to build up enough to support his weight.

157) Describe the structures of a sarcomere.

A sarcomere consists of thin and thick filaments arranged so they can slide over each other. The boundary of the sarcomere are the Z lines. Thin filaments extend from the Z lines and overlap with thick filaments in the middle of the sarcomere. The I band is on each side of the Z line where only thin filaments occur. The A band is the length of the thick filaments and is divided into three parts; the zone of overlap is on each end where thin and thick filaments occur, the H band is in the middle and has only thick filaments, and the M line is the center of the A band.

102) After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs. A) an oxygen debt B) paralysis C) treppe D) tetanus E) atrophy

A) an oxygen debt

106) Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to A) repeated, exhaustive stimulation. B) sustained low levels of muscle activity. C) high amounts of oxygen. D) increased levels of testosterone. E) prolonged periods of inactivity.

A) repeated, exhaustive stimulation.

113) The muscle weakness of myasthenia gravis results from A) insufficient acetylcholine release from presynaptic vesicles. B) loss of acetylcholine receptors in the end-plate membrane. C) the motor neuron action potential being too small to shock the muscle fibers. D) excessive acetylcholinesterase that destroys the neurotransmitter. E) All of the answers probably contribute to the muscle weakness.

B) loss of acetylcholine receptors in the end-plate membrane.

105) The type of muscle fiber that is most resistant to fatigue is the ________ fiber. A) fast B) slow C) intermediate D) anaerobic E) high-density

B) slow

110) Which of the following is not a type of motor fiber? A) pink-fast twitch B) white-slow twitch C) white-fast twitch D) red-slow twitch E) type I

B) white-slow twitch

104) During the recovery period, the body's need for oxygen is increased because A) muscle cells are producing energy anaerobically. B) the individual is panting. C) additional oxygen is required to restore energy reserves consumed during exercise. D) the liver requires more oxygen to produce lactic acid. E) the muscles are not producing ATP.

C) additional oxygen is required to restore energy reserves consumed during exercise.

107) Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of A) slow fibers. B) intermediate fibers. C) fast fibers. D) red muscles. E) fatty muscles.

C) fast fibers.

103) During the Cori cycle, in the liver, A) glucose is released from glycogen. B) lactate is produced from glucose. C) glucose is produced from lactate. D) lactate is produced from pyruvic acid. E) lactate is shuffled to muscle cells

C) glucose is produced from lactate.

111) Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass? A) epinephrine B) thyroid hormone C) testosterone D) parathyroid hormone E) calcitonin

C) testosterone

114) Of the following clinical conditions affecting skeletal muscle, which is caused by a virus? A) tetanus B) botulism C) Duchenne muscular dystrophy D) polio E) rigor mortis

D) polio

112) After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as A) tetany. B) treppe. C) depolarization. D) rigor mortis. E) oxygen debt.

D) rigor mortis.

108) Which of the following statements is/are not true regarding human muscles? A) Most have both slow and fast fibers. B) Slow fibers are abundant in the calf muscles. C) Eye muscles are composed entirely of fast fibers. D) Slow fibers are abundant in the back muscles. E) Fast fibers are high in myoglobin.

E) Fast fibers are high in myoglobin.

109) When comparing slow fibers to fast fibers, slow fibers A) take less time to reach peak tension. B) have much larger fiber diameters. C) generate much more tension. D) are lacking myoglobin. E) appear dark red.

E) appear dark red.

101) Which of these would not lead to increased oxygen consumption? A) increased heat production B) increased conversion of lactic acid to glucose C) increased aerobic respiration by muscle cells D) increased muscle activity E) lactic acidosis

E) lactic acidosis

152) A hypothetical genetic disease causes the body to produce antibodies that compete with acetylcholine for receptors on the motor end plate. Patients with this disease exhibit varying degrees of muscle weakness and flaccid paralysis in the affected muscles. If you could administer a drug that inhibits acetylcholinesterase or a drug that blocks acetylcholine, which one would you use to alleviate these symptoms?

I would use the drug that blocks acetylcholine

158) How would a drug that blocks acetylcholine release affect muscle contraction?

If a drug blocked the binding of ACh to receptors at the motor end plates of neuromuscular junctions, the muscle's ability to contract would be inhibited

154) Thirty minutes after Mary has completed a 25-km race, she begins to notice severe muscle soreness and stiffness in her legs. Her urine is dark colored. She wonders whether she may have damaged her muscles during the race. She visits the ER, and the doctor orders several blood tests. What kind of blood tests can help determine whether muscle damage has occurred?

If muscle damage occurred, the doctor would find enzymes such as creatine phosphokinase and proteins such as myoglobin or troponin in the bloodstream released by injured skeletal muscle cells. The level of these substances correlates with the severity of the injury.

162) Explain how the flexibility or rigidity of a dead body can provide a clue about a murder victim's time of death.

In rigor mortis, the membranes of the dead cells are no longer selectively permeable; the SR is no longer able to retain calcium ions. As calcium ions enter the sarcoplasm, a sustained contraction develops, making the body extremely stiff. Contraction persists because the dead muscle cells can no longer make the ATP required for cross-bridge detachment from the active sites. Rigor mortis begins a few hours after death and lasts 15-25 hours, until the lysosomal enzymes released by autolysis break down the microfilaments.

160) Describe the events that occur during each phase of a twitch in a stimulated muscle fiber.

Muscle twitch: single stimulus contraction relaxation sequence in a muscle fiber. Duration caries by muscle type, location, environmental factors. Fasciculation= involuntary, "muscle twitch" under skin. Myogram= shows development of muscle tension. 1. Latent period..action potential stimulates sarcolemma, calcium released from sarcoplasmic reticulum, no tension yet. 2. Contraction phase..calcium binds

156) How would severing a tendon attached to a muscle affect movement of that limb?

Neurotransmitters will be unable to be sent to that part of the body, not allowing movement

151) Describe the basic sequence of events that occurs at the neuromuscular junction and in the muscle cell during excitation and excitation-contraction coupling.

The action potential triggers the exocytosis of neurotransmitters stored in vesicles in the axon ending. This acetylcholine binds to receptors in the motor end plate, increasing the muscle membrane permeability to sodium. Acetylcholinesterase destroys the acetylcholine, ensuring that each nerve action potential produces only a single twitch. The influx of these positive sodium ions triggers an action potential. The action potential spreads in both directions away from the end plate across the entire surface of the muscle fiber and into the interior via transverse tubules, triggering a pulse of calcium ion release from the sarcoplasmic reticulum, which generates a brief small twitch. With additional stimuli, calcium ion builds up and higher tensions are produced.

155) Mary wants to enter a weight-lifting competition and consults you as to what type of muscle fibers she needs to develop and how she should go about it. What would you suggest to her?

Weight lifting requires anaerobic endurance. Mary would want to develop her fast fibers for short-term maximum strength. She would achieve this by engaging in activities that involve frequent, brief, but intensive workouts, such as with heavy weights to the point of muscle fatigue. The fatigue triggers the production of new myofilament proteins, leading to muscle bulk and strength.

153) Describe a motor unit. How many fibers does a muscle unit contain?

all of the muscle cells controlled by a single motor neuron. The muscle fibers are all controlled by motor units. When you decide to do a specific function motor neurons in the spinal cord are stimulated, the contraction begins with the activation of the smallest motor units in the stimulated area. These units normally contain muscle fibers that contract slowly, but as the movement continues larger motor units are activated and tension rises. This increase in tension produced by the rising number of motor units is recruitment.

74) Which statement about excitation-contraction coupling is incorrect? A) Calcium ion is released from the transverse tubule. B) Calcium ion is released from the sarcoplasmic reticulum. C) Tropomyosin moves to expose myosin binding sites on actin. D) Troponin binds calcium ion and signals tropomyosin to move. E) Relaxation requires uptake of calcium ions by the sarcoplasmic reticulum.

A) Calcium ion is released from the transverse tubule.

13) ________ are stem cells located between the endomysium and sarcolemma that function in the repair of damaged muscle tissue. A) Myosatellite cells B) Myofilaments C) Myofibrils D) Multinucleate cells E) Myoblasts

A) Myosatellite cells

86) Which of the following motor units would produce the greatest tension? A) a motor unit in a back muscle B) a motor unit in a hand muscle C) a motor unit in an eye muscle

A) a motor unit in a back muscle

71) Which of the following become connected by myosin cross-bridges during muscle contraction? A) thin filaments and thick filaments B) thick filaments and titin filaments C) Z disks and actin filaments D) thick filaments and T tubules E) thin filaments and T tubules

A) thin filaments and thick filaments

69) When calcium ion binds to troponin, A) tropomyosin moves into the groove between the helical actin strands. B) active sites on the myosin are exposed. C) troponin shifts to expose the active sites on actin. D) muscle relaxation occurs. E) myosin shortens.

A) tropomyosin moves into the groove between the helical actin strands.

35) Each thin filament consists of A) two protein strands coiled helically around each other. B) chains of myosin molecules. C) six molecules in a rod-like structure. D) a rod-shaped structure with "heads" projecting from each end. E) a double strand of myosin molecules.

A) two protein strands coiled helically around each other

23) Where are the myosin molecules located? A) 4 B) 5 C) 6 D) 7 E) 8 ** look at doc

B) 5

33) In a sarcomere, thick filaments are linked laterally by proteins of the A) Z line. B) M line. C) H band. D) A band. E) I band.

B) M line.

41) When a skeletal muscle fiber contracts, which of the following does not occur? A) The H bands and I bands get smaller. B) The zones of overlap get larger. C) The Z lines get closer together. D) The width of the A band remains constant. E) Myosin and actin filaments decrease in length.

B) The zones of overlap get larger.

90) What is thought to happen in a muscle during the response shown in graph (a)? A) It is strengthening with exercise. B) There is a gradual increase in the concentration of calcium ions in the sarcoplasm. C) It is fatigued and must make repeated efforts to twitch normally. D) It is aged and has lost contractile proteins. E) It is producing more ATP as tension increases. ** look at doc

B) There is a gradual increase in the concentration of calcium ions in the sarcoplasm.

85) Which of the following muscles would contract more forcefully? A) a muscle receiving 10 to 15 action potentials per second B) a muscle receiving 20 to 25 action potentials per second

B) a muscle receiving 20 to 25 action potentials per second

21) The skeletal muscle complex known as the triad consists of A) actin, myosin, and sarcomeres. B) a transverse tubule and two terminal cisternae. C) filaments, myofibrils, and muscle fibers. D) A bands, H bands, and I bands. E) a terminal cisterna and two transverse tubules.

B) a transverse tubule and two terminal cisternae.

70) The most important factor in decreasing the intracellular concentration of calcium ion after contraction is A) active transport of calcium across the sarcolemma. B) active transport of calcium back into the sarcoplasmic reticulum. C) active transport of calcium into the synaptic cleft. D) diffusion of calcium out of the cell. E) diffusion of calcium into the sarcoplasmic reticulum.

B) active transport of calcium back into the sarcoplasmic reticulum.

66) Which process employs exocytosis? A) facilitated diffusion B) chemical synapse C) depolarization D) antagonist binding E) cross-bridge formation

B) chemical synapse

78) When a muscle is stimulated repeatedly at a high rate, eliminating a relaxation phase, the amount of tension gradually increases to a steady maximum tension. This is called A) incomplete tetanus. B) complete tetanus. C) a twitch. D) wave summation. E) recruitment

B) complete tetanus.

27) What physiological process occurs in the structure labeled "7"? A) release of acetylcholine B) conduction of the action potential toward the triad C) acetylcholinesterase breakdown of acetylcholine D) release of proteins into the muscle fiber E) the sliding of actin and myosin filaments ** look at doc

B) conduction of the action potential toward the triad

40) Physical evidence that supports the sliding filament theory of muscle contraction includes A) constant distance between Z lines during contraction. B) decreased width of the H band during contraction. C) increased width of the I band during contraction. D) decreased width of the A band during contraction. E) the I band and H band distance is constant during contraction.

B) decreased width of the H band during contraction.

50) During the ________ phase of action potential development, voltage-gated sodium channels are open. A) repolarization B) depolarization C) refractory D) threshold

B) depolarization

4) The dense layer of connective tissue that surrounds an entire skeletal muscle is the A) tendon. B) epimysium. C) endomysium. D) perimysium. E) fascicle

B) epimysium.

8) Muscle fibers differ from "typical cells" in that muscle fibers A) lack a plasma membrane. B) have many nuclei. C) are very small. D) lack mitochondria. E) All of the answers are correct.

B) have many nuclei.

57) Receptors for acetylcholine are located on the A) synaptic knob. B) motor end plate. C) sarcomere. D) synaptic cleft. E) transverse tubule.

B) motor end plate.

53) Neurons and ________ have electrically excitable membranes that propagate action potentials. A) osteocytes B) muscle cells C) epithelial cells D) proteins E) dense connective tissue

B) muscle cells

87) To produce a contraction similar to the one in graph (b), the muscle A) must be stimulated to the point of fatigue. B) must be stimulated again before it has relaxed from the previous stimulation. C) is excited by a stimulus of increasing intensity. D) is caused to produce isolated twitches. E) gradually warms up. ** look at doc

B) must be stimulated again before it has relaxed from the previous stimulation.

38) At rest, the tropomyosin molecule is held in place by A) actin molecules. B) myosin molecules. C) troponin molecules. D) ATP molecules. E) calcium ions.

B) myosin molecules.

44) Cross-bridges are portions of A) actin molecules. B) myosin molecules. C) troponin molecules. D) tropomyosin molecules. E) calcium ions.

B) myosin molecules.

68) Communication between axons and muscle fibers occurs at specialized synapses called A) junctional folds. B) neuromuscular junctions. C) motor end plates. D) active sites. E) Z lines.

B) neuromuscular junctions.

5) Nerves and blood vessels that service the muscle fibers are located in the connective tissues of the A) endomysium. B) perimysium. C) sarcolemma. D) sarcomere. E) myofibrils.

B) perimysium.

16) The repeating contractile unit of a skeletal muscle fiber is the A) sarcolemma. B) sarcomere. C) sarcoplasmic reticulum. D) myofibril. E) myofilament.

B) sarcomere.

42) Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber A) lengthens. B) shortens. C) strengthens. D) weakens. E) There is insufficient information to determine the answer.

B) shortens.

73) Which of the following is greater? A) the concentration of calcium ion in the sarcoplasm of a resting muscle B) the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle

B) the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle

65) How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle? A) It would make the muscles less excitable. B) It would produce muscle weakness. C) It would cause spastic paralysis (muscles are contracted and unable to relax). D) It would cause flaccid paralysis (muscles are relaxed and unable to contract). E) It would have little effect on skeletal muscles.

C) It would cause spastic paralysis (muscles are contracted and unable to relax).

2) Which of the following statements is incorrect? A) The contractions of skeletal muscles pull on tendons and move bones of the skeleton. B) Skeletal muscles store nutrient reserves. C) Skeletal muscles are responsible for the pumping action of the heart. D) Skeletal muscles support the weight of some internal organs. E) Skeletal muscle contractions help maintain body temperature.

C) Skeletal muscles are responsible for the pumping action of the heart.

61) The cytoplasm of the neuromuscular synaptic terminal contains vesicles filled with molecules of the neurotransmitter A) epinephrine. B) norepinephrine. C) acetylcholine. D) antidiuretic hormone. E) acetylcholinesterase.

C) acetylcholine.

95) Creatine phosphate A) is produced by the process of anaerobic respiration. B) can replace ATP in binding to myosin molecules during contraction. C) acts as an energy reserve in muscle tissue. D) is only formed during strenuous exercise. E) cannot transfer its phosphate group to ADP.

C) acts as an energy reserve in muscle tissue.

94) A resting muscle generates most of its ATP by A) hydrolysis of creatine phosphate. B) anaerobic respiration. C) aerobic metabolism of fatty acids. D) glycogenolysis. E) the tricarboxylic acid cycle.

C) aerobic metabolism of fatty acids.

100) Decreased blood flow to a muscle could result in all of the following except A) muscle fatigue. B) an oxygen debt. C) an increase in intracellular glycogen. D) a shift to anaerobic glycolysis. E) an increase in intracellular lactate.

C) an increase in intracellular glycogen.

60) Synaptic vesicles containing neurotransmitters are released by ________ when the action potential arrives. A) endocytosis B) apoptosis C) exocytosis D) hydrolysis E) sodium

C) exocytosis

48) The Na+/K+ ion pump is responsible for A) diffusing chloride across the plasma membrane. B) transferring messages from enzyme-linked receptors to the cell nucleus. C) maintaining the sodium/potassium concentration gradients constant. D) initiating action potentials. E) amplifying signals using ATP.

C) maintaining the sodium/potassium concentration gradients constant.

99) During activities requiring aerobic endurance, A) glycogen and glycolysis are the primary sources of reserve energy. B) oxygen debts are common. C) most of the muscle's energy is produced in mitochondria. D) fatigue occurs in a few minutes. E) oxygen is not required.

C) most of the muscle's energy is produced in mitochondria.

81) A single motor neuron together with all the muscle fibers it innervates is called a(n) A) end foot. B) end plate. C) motor unit. D) dermatome. E) myotome.

C) motor unit.

32) Interactions between actin and myosin filaments of the sarcomere are responsible for A) muscle fatigue. B) the conduction of neural stimulation to the muscle fiber. C) muscle contraction. D) muscle relaxation. E) the striped appearance of skeletal muscle.

C) muscle contraction.

84) In which of the following would the motor units have the fewest muscle fibers? A) muscles of the neck B) postural muscles of the back C) muscles that control the eyes D) thigh muscles E) calf muscles

C) muscles that control the eyes

10) Skeletal muscle fibers are formed from embryonic cells called A) sarcomeres. B) myofibrils. C) myoblasts. D) fascicles. E) myomeres.

C) myoblasts.

55) Each skeletal muscle fiber is controlled by a motor neuron at a single A) synaptic knob. B) sarcomere. C) neuromuscular junction. D) synaptic cleft. E) transverse tubule.

C) neuromuscular junction.

43) The structural explanation of how a muscle fiber contracts is called the A) myosin spiral theory. B) thin filament theory. C) sliding filament theory. D) cross-bridge connection. E) active site rule.

C) sliding filament theory.

15) Which of the following best describes the sarcoplasmic reticulum? A) protein that accounts for elasticity of resting muscle B) repeating unit of striated myofibrils C) storage and release site for calcium ions D) thin filaments are anchored here E) largely made of myosin molecules

C) storage and release site for calcium ions

46) Membrane potential is A) a chemical signal that has not yet bound to a receptor. B) a cell's capacity to respond to a chemical signal. C) the electrical gradient of a cell. D) the site of signal transfer between two cells. E) the period when the membrane cannot respond to another stimulus.

C) the electrical gradient of a cell.

58) The action potential is conducted into a skeletal muscle fiber by A) motor end plates. B) neuromuscular junctions. C) transverse tubules. D) triads. E) sarcoplasmic reticulum.

C) transverse tubules.

37) At rest, active sites on the actin are blocked by A) myosin molecules. B) troponin molecules. C) tropomyosin molecules. D) calcium ions. E) ATP molecules.

C) tropomyosin molecules.

75) The rapid rise and fall in force produced by a muscle fiber after a single action potential is a(n) A) tetanus. B) unfused tetanus. C) twitch. D) end plate potential. E) muscle action potential.

C) twitch.

98) Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell. A) 25 B) 50 C) 70 D) 95 E) 100

D) 95

18) The region of the sarcomere containing the thick and thin filaments is the A) Z line. B) M line. C) H band. D) A band. E) I band.

D) A band.

25) What is released from the structure labeled "9"? A) sodium B) acetylcholine C) proteins D) calcium ions E) acetylcholinesterase ** look at doc

D) calcium ions

59) In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases A) acetylcholine. B) sodium ions. C) potassium ions. D) calcium ions. E) hydrogen ions.

D) calcium ions.

77) The synchronous contraction of a single motor unit is known as a(n) A) twitch. B) asynchronous motor unit summation. C) cross-bridge. D) fasciculation. E) muscle action potential.

D) fasciculation.

49) Na+ and K+ both use ________ to passively diffuse across the plasma membrane. A) facilitated diffusion B) exocytosis C) voltage-gated channels D) leak channels E) carrier-mediated transport

D) leak channels

45) Cellular membrane potential is measured in A) milliseconds. B) micrometers. C) Hertz. D) millivolts. E) amperes.

D) millivolts.

97) At peak levels of muscle exertion, the mitochondria can supply ________ of the energy required by the muscle. A) all B) 80 percent C) more than half D) only about one-third E) only about 10 percent

D) only about one-third

9) The advantage of having many nuclei in a skeletal muscle fiber is the ability to A) contract. B) produce more ATP with little oxygen. C) store extra DNA for metabolism. D) produce large amounts of the muscle proteins needed for muscle contraction. E) All of the answers are correct.

D) produce large amounts of the muscle proteins needed for muscle contraction.

67) Excitation-contraction coupling is the A) sliding of thin filaments past thick filaments during muscle fiber contraction. B) refractory period of an action potential. C) threshold period of an action potential. D) sequence of processes that links the action potential to contraction. E) transfer of ACh into the synaptic cleft.

D) sequence of processes that links the action potential to contraction.

56) The narrow space between the synaptic terminal and the muscle fiber is the A) synaptic knob. B) motor end plate. C) motor unit. D) synaptic cleft. E) M line.

D) synaptic cleft.

72) Which of the following acts as an ATPase during the contraction cycle of muscle? A) actin molecules B) troponin molecules C) tropomyosin molecules D) the head portion of the myosin molecule E) the tail portion of the myosin molecule

D) the head portion of the myosin molecule

31) The complex of a transverse tubule and two adjacent terminal cisternae is known as a(n) A) free head. B) zone of overlap. C) M line. D) triad. E) sarcomere.

D) triad

80) If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This is called A) incomplete tetanus. B) complete tetanus. C) treppe. D) wave summation. E) recruitment.

D) wave summation.

34) Which of the following best describes the term "Z line"? A) protein that accounts for elasticity of resting muscle B) repeating unit of striated myofibrils C) storage site for calcium ions D) where thin filaments are anchored E) largely made of myosin molecules

D) where thin filaments are anchored

19) The region of the sarcomere that always contains only thin filaments is the A) Z line. B) M line. C) H band. D) A band. E) I band.

E) I band.

96) During anaerobic glycolysis, which of the following does not occur? A) ATP is produced. B) Pyruvate is produced. C) Oxygen is not consumed. D) The mitochondria are required. E) Lactate is produced.

E) Lactate is produced.

88) Why is there partial relaxation in graph (c)? A) Calcium ion release is slow. B) The muscle is starting to fatigue. C) Stimulation intensity is fluctuating. D) ATP reserves are cycling. E) Maximum tension is below maximum. ** look at doc

E) Maximum tension is below maximum.

30) Which statement about the microscopic anatomy of skeletal muscle fibers is not true? A) Tubular extensions of the sarcolemma penetrate the fiber transversely. B) Cross striations result from the lateral alignment of thick and thin filaments. C) Each fiber has many nuclei. D) Muscle fibers are continuous from tendon to tendon. E) Multiple myofibrils link end-to-end along length of the muscle cell.

E) Multiple myofibrils link end-to-end along length of the muscle cell.

83) Muscular force can be adjusted to match increased loads by A) increasing the frequency of action potentials in motor neurons. B) recruiting smaller motor units. C) recruiting fewer motor units. D) decreasing the frequency of action potentials in motor neurons. E) None of the answers is correct.

E) None of the answers is correct.

54) Which of the following statements is not true about action potentials? A) They can travel long distances within cells. B) They occur in neurons. C) They end in repolarization. D) They can be generated in less than 2 msec. E) They can travel in two directions.

E) They can travel in two directions.

1) Which of the following is not a recognized function of skeletal muscle? A) produce movement B) maintain posture C) maintain body temperature D) guard body entrances and exits E) controlled involuntarily

E) controlled involuntarily

17) Each skeletal muscle fiber contains ________ myofibrils. A) 50 to 100 B) 100 to 150 C) 150 to 200 D) 200 to 500 E) hundreds to thousands

E) hundreds to thousands

52) If the membrane potential of a neuron is -80 mV, it is A) at resting potential. B) at threshold. C) depolarized. D) repolarized. E) hyperpolarized during the refractory period

E) hyperpolarized during the refractory period

91) The type of contraction in which the muscle fibers do not shorten is called A) tetany. B) treppe. C) concentric. D) isotonic. E) isometric.

E) isometric.

22) Which of the following is not found in the structure labeled "3"? A) actin B) myosin C) titin D) tropomyosin E) mitochondria **look at doc

E) mitochondria

82) The increase in muscle tension that is produced by increasing the number of active motor units is called A) incomplete tetanus. B) complete tetanus. C) treppe. D) wave summation. E) recruitment.

E) recruitment.

39) Which of the following proteins is not found as a part of thin filaments? A) actin B) tropomyosin C) troponin D) nebulin E) titin

E) titin