Chapter 11 Muscle Tissue Practice Question
35) Which of the following become connected by myosin cross-bridges during muscle contraction? A) thick filaments and t-tubules B) thick filaments and titin filaments C) thin filaments and thick filaments D) thin filaments and t-tubules E) z disks and actin filaments
C
79) Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of A) red muscles. B) intermediate fibers. C) fast fibers. D) fatty muscles. E) slow fibers.
C
58) When comparing slow motor units to fast motor units, slow units A) take about three times as long to reach peak tension. B) are rich in the red protein myoglobin. C) generate much less tension. D) have much smaller fiber diameters. E) all of the above
E
63) The ability of smooth muscle to function over a wide range of lengths is called A) variability. B) elasticity. C) contractility. D) extensibility. E) plasticity.
E
68) The thin filaments of striated muscle are made of which protein(s)? A) tropomyosin B) troponin C) actin D) nebulin E) all of the above
E
14) Interactions between actin and myosin filaments of the sarcomere are responsible for A) muscle contraction. B) the striped appearance of skeletal muscle. C) the conduction of neural stimulation to the muscle fiber. D) muscle relaxation. E) muscle fatigue.
A
5) The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the A) endomysium. B) perimysium. C) periosteum. D) superficial fascia. E) epimysium.
AD
15) In a sarcomere, thick filaments are linked laterally by proteins of the A) I band. B) M line. C) H band. D) Z line. E) A band.
B
62) Which of the following is not a function of smooth muscle tissue? A) moving food materials along the digestive tract B) forcing blood from the heart into the major arteries C) altering the diameter of the respiratory passageways D) elevating hairs on the arm E) forcing urine out of the urinary tract
B
65) The types of muscle tissue include all of the following, except A) cardiac muscle. B) skeletal muscle. C) striated muscle. D) smooth muscle. E) none of the above
B
66) At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a A) satellite cell. B) tendon. C) sheath. D) ligament. E) tenosynovium.
B
78) The contraction of a muscle exerts a pull on a bone because A) muscles are attached to bones by ligaments. B) muscles are attached to bones by tendons. C) muscles are attached to bones by bursae. D) A or C E) A, B, or C
B
9) Skeletal muscle fibers are formed from embryonic cells called A) myomeres. B) myoblasts. C) myofibrils. D) sarcomeres. E) fascicles.
B
92) In which of the following would the motor units have the fewest muscle fibers? A) muscles of the neck B) muscles that control the eyes C) thigh muscles D) postural muscles of the back E) calf muscles
B
10) The plasma membrane of skeletal muscle is called the A) sarcosome. B) sarcomere. C) sarcolemma. D) sarcoplasmic reticulum. E) sarcoplasm.
C
22) The skeletal muscle complex known as the triad consists of A) filaments, myofibrils, and sarcomeres. B) actin, myosin, and filaments. C) a transverse tubule and two terminal cisternae. D) actin, myosin, and sarcomeres. E) A bands, H bands, and I bands.
C
28) Receptors for acetylcholine are located on the A) synaptic cleft. B) transverse tubule. C) motor end plate. D) synaptic knob. E) sarcomere.
C
38) When a muscle is stimulated repeatedly at a high rate, the amount of tension gradually increases to a steady maximum tension. This is called A) a twitch. B) recruitment. C) complete tetanus. D) wave summation. E) incomplete tetanus. 38)
C
11) Which of the following best describes the term sarcomere? A) largely made of myosin molecules B) protein that accounts for elasticity of resting muscle C) storage site for calcium ions D) repeating unit of striated myofibrils E) thin filaments are anchored here
D
13) The repeating unit of a skeletal muscle fiber is the A) myofibril. B) myofilament. C) sarcoplasmic reticulum. D) sarcomere. E) sarcolemma.
D
122) Match the term with its description. 1. thyroid hormone 2. testosterone 3. epinephrine 4. myoglobin 5. calmodulin A) primary sex hormone in males B) elevates the rate of energy consumption in resting and active skeletal muscles C) stimulates muscle metabolism and increases duration and stimulation of the force of a contraction D) activates myosin light chain kinase E) red pigment in slow fibers
1-B; 2-A; 3-C; 4-E; 5-D
123) Match the term with its description. 1. skeletal muscle 2. muscle fascicle 3. muscle fiber 4. myofibril 5. sarcomere A) surrounded by endomysium and contains myofibrils B) surrounded by sarcoplasmic reticulum and consists of sarcomeres C) surrounded by epimysium and contains muscle fascicles D) surrounded by perimysium and contains muscle fibers E) contains thick and thin filaments
1-C; 2-D; 3-A; 4-B; 5-E
131) Describe the basic sequence of events that occurs at the neuromuscular junction and in the muscle cell.
131) 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.
100) The muscle weakness of myasthenia gravis results from A) loss of acetylcholine receptors in the end-plate membrane. B) excessive acetylcholinesterase that destroys the neurotransmitter. C) insufficient acetylcholine release from presynaptic vesicles. D) the motor neuron action potential being too small to shock the muscle fibers. E) All of the above probably contribute to the weakness.
A
20) Each thin filament consists of A) two protein strands coiled helically around each other. B) six molecules coiled into a helical structure. C) chains of myosin molecules. D) a rod-shaped structure with "heads" projecting from each end. E) a double strand of myosin molecules.
A
27) The narrow space between the synaptic terminal and the muscle fiber is the A) synaptic cleft. B) M line. C) motor end plate. D) synaptic knob. E) motor unit.
A
34) The most important factor in decreasing the intracellular concentration of calcium ion after contraction is A) active transport of calcium into the sarcoplasmic reticulum. B) active transport of calcium across the sarcolemma. C) diffusion of calcium into the sarcoplasmic reticulum. D) active transport of calcium into the synaptic cleft. E) diffusion of calcium out of the cell.
A
37) The rapid rise and fall in force produced by a muscle fiber after a single action potential is A) a twitch. B) an end plate potential. C) a tetanus. D) a muscle action potential. E) an unfused tetanus. 37)
A
53) The type of muscle fiber that is most resistant to fatigue is the ________ fiber. A) slow B) fast C) intermediate D) high-density E) anaerobic
A
56) 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) prolonged periods of inactivity. E) increased levels of testosterone.
A
59) Heat energy produced from muscle contraction is released by the ________ system. A) integumentary B) respiratory C) urinary D) cardiovascular E) all of the above
A
60) Which of the following statements is false? A) Cardiac muscle stimulation is neural. B) Skeletal muscle stimulation is neural. C) Skeletal muscle contractions may be summated. D) Cardiocytes are interconnected through intercalated discs. E) Cardiac muscle contractions cannot be summated.
A
7) Muscle fibers differ from "typical cells" in that muscle fibers A) have many nuclei. B) lack mitochondria. C) are very small. D) lack a plasma membrane. E) both B and C
A
74) The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter A) acetylcholine. B) epinephrine. C) antidiuretic hormone. D) norepinephrine. E) all of the above
A
86) Which of the following is greater? A) the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle B) the concentration of calcium ion in the sarcoplasm of a resting muscle
A
87) The following is a list of the events that occur during a muscle contraction. 1. Myosin cross-bridges bind to the actin. 2. The free myosin head splits ATP. 3. Calcium ion is released from the sarcoplasmic reticulum. 4. The myosin head pivots toward the center of the sarcomere. 5. Calcium ion binds to troponin. 6. The myosin head binds an ATP molecule and detaches from the actin. The correct sequence of these events is A) 3, 5, 1, 4, 6, 2. B) 1, 4, 6, 2, 3, 5. C) 5, 1, 4, 6, 2, 3. D) 3, 5, 1, 2, 4, 6. E) 1, 3, 5, 4, 6, 2.
A
91) Triggering of the muscle action potential occurs after A) acetylcholine binds to chemically gated channels in the end plate membrane. B) calcium ion binds to channels on the end plate. C) acetylcholinesterase binds to receptors on the end plate. D) the nerve action potential jumps across the neuromuscular junction. E) Any of the above can produce an action potential in the muscle cell.
A
93) Which of the following muscles would contract more forcefully? A) a muscle receiving 20 to 25 action potentials per second B) a muscle receiving 10 to 15 action potentials per second
A
135) Describe a motor unit. How many fibers does a muscle unit contain? 20
A motor unit consists of all the skeletal muscle fibers controlled by a single motor neuron. They may have as few as 10 fibers (eye muscles) or as many as 10,000 (back muscles).
106) Where are the myosin molecules located? A) 4 B) 5 C) 6 D) 7 E) 8
B
107) Which structure contains the motor end plate? A) 1 B) 2 C) 3 D) 5 E) 8
B
112) To produce a contraction similar to the one in graph (b), the muscle A) gradually warms up. B) must be stimulated again before it has relaxed from the previous stimulation. C) is caused to produce isolated twitches. D) must be stimulated to the point of fatigue. E) is excited by a stimulus of increasing intensity.
B
115) What is the contraction in graph (a) called? A) twitch B) treppe C) complete tetanus D) wave summation E) incomplete tetanus
B
16) Which of the following best describes the term Z line? A) storage site for calcium ions B) thin filaments are anchored here C) protein that accounts for elasticity of resting muscle D) repeating unit of striated myofibrils E) largely made of myosin molecules
B
17) The region of the sarcomere containing the thick filaments is the A) Z line. B) A band. C) H band. D) M line. E) I band.
B
26) Each skeletal muscle fiber is controlled by a motor neuron at a single A) synaptic knob. B) neuromuscular junction. C) sarcomere. D) transverse tubule. E) synaptic cleft.
B
39) A muscle producing tension that peaks and falls at intermediate stimulus rates is said to be in A) recruitment. B) incomplete tetanus. C) treppe. D) complete tetanus. E) wave summation. 39)
B
41) A single motor neuron together with all the muscle fibers it innervates is called A) an end foot. B) a motor unit. C) a myotome. D) an end plate. E) a dermatome.
B
43) The type of contraction in which the muscle fibers do not shorten is called A) tetany. B) isometric. C) treppe. D) isotonic. E) concentric.
B
45) Creatine phosphate A) is only formed during strenuous exercise. B) acts as an energy reserve in muscle tissue. C) is produced by the process of anaerobic respiration. D) can replace ATP in binding to myosin molecules during contraction. E) cannot transfer its phosphate group to ADP.
B
49) During the recovery period following exercise, all of the following are true, except A) lactic acid is removed from muscle cells. B) muscle fibers are unable to contract. C) oxygen is consumed at above the resting rate. D) the muscle actively produces ATP. E) heat is generated.
B
61) Which of the following is not characteristic of smooth muscle? A) The thin filaments of smooth muscle fibers are attached to dense bodies. B) Smooth muscle connective tissue forms tendons and aponeuroses. C) Smooth muscles are uninucleate. D) Neurons that innervate smooth muscles are under involuntary control. E) Smooth muscles do not contain sarcomeres.
B
101) Which of the following best describes the term muscle origin? A) tendon attachment that moves B) connective tissue that surrounds a single muscle fiber C) tendon attachment that doesn't move D) broad tendon sheet E) connective tissue that surrounds an entire muscle
C
114) What is the contraction in graph (d) called? A) twitch B) wave summation C) complete tetanus D) incomplete tetanus E) treppe
C
40) If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This is called A) recruitment. B) incomplete tetanus. C) wave summation. D) treppe. E) complete tetanus.
C
47) At peak levels of muscle exertion the mitochondria can supply A) more than half of the energy required by the muscle. B) 80 percent of the energy required by the muscle. C) only about one-third of the energy required by the muscle. D) all of the energy required by the muscle. E) only about 10 percent of the energy required by the muscle.
C
64) Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for A) conduction. B) cushioning C) contraction. D) peristalsis. E) any of the above
C
77) In an isotonic contraction, A) the peak tension is less than the load. B) many twitches fuse into one. C) muscle tension exceeds the load and the muscle lifts the load. D) flexion is produced. E) tension rises and falls but the muscle length is constant.
C
8) The advantage of having many nuclei in a skeletal muscle fiber is A) the ability to contract. B) the ability to store extra DNA for metabolism. C) the ability to produce large amounts of the muscle proteins needed for growth and repair. D) the ability to produce more ATP with little oxygen. E) both C and D
C
94) Which of the following motor units would produce the greatest tension? A) a motor unit in an eye muscle B) a motor unit in a hand muscle C) a motor unit in a back muscle
C
95) Decreased blood flow to a muscle could result in all of the following, except A) muscle fatigue. B) a shift to anaerobic glycolysis. C) an increase in intracellular glycogen. D) an increase in intracellular lactate. E) an oxygen debt.
C
98) How would a drug that blocks acetylcholine receptors at the motor end plate affect skeletal muscle? A) It would cause spastic paralysis (muscles are contracted and unable to relax). B) It would produce uncontrolled muscle spasms. C) It would cause flaccid paralysis (muscles are relaxed and unable to contract). D) It would have little effect on skeletal muscles. E) It would make the muscles more excitable.
C
99) Synaptic vesicles containing neurotransmitters are released by ________ when the action potential arrives. A) endocytosis B) sodium C) exocytosis D) hydrolysis E) apoptosis
C
103) Identify the structure labeled "1." A) myofibril B) glycogen C) ATP D) mitochondria E) synaptic vesicle
D
113) Why is there partial relaxation in graph (c)? A) The muscle is starting to fatigue. B) ATP reserves are cycling. C) Calcium ion release is slow. D) Nerve stimulation frequency is below maximum. E) Stimulation intensity is fluctuating.
D
116) What is thought to happen in a muscle during the response shown in graph (a)? A) It is aged and has lost contractile proteins. B) It is producing more ATP as tension increases. C) It is getting stronger with exercise. D) There is a gradual increase in the concentration of calcium ions in the sarcoplasm. E) It is fatigued and must make repeated efforts to twitch normally.
D
2) Which of the following statements is incorrect? A) Skeletal muscles store nutrient reserves. B) The contractions of skeletal muscles pull on tendons and move bones of the skeleton. C) Skeletal muscles support the weight of some internal organs. D) Skeletal muscles are responsible for the pumping action of the heart. E) Skeletal muscle contractions help maintain body temperature.
D
23) Cross-bridges are portions of A) troponin molecules. B) actin molecules. C) calcium ions. D) myosin molecules. E) tropomyosin molecules.
D
24) At rest, active sites on the actin are blocked by A) calcium ions. B) troponin molecules. C) myosin molecules. D) tropomyosin molecules. E) ATP molecules.
D
3) The dense layer of connective tissue that surrounds an entire skeletal muscle is the A) tendon. B) perimysium. C) fascicle. D) epimysium. E) endomysium.
D
30) Active sites on the actin become available for binding after A) myosin binds to troponin. B) actin binds to troponin. C) troponin binds to tropomyosin. D) calcium binds to troponin. E) calcium binds to tropomyosin.
D
32) Which of the following acts as an ATPase during the contraction cycle of muscle? A) troponin molecules B) the tail portion of the myosin molecule C) tropomyosin molecules D) the head portion of the myosin molecule E) actin molecules
D
33) When calcium ion binds to troponin, A) muscle relaxation occurs. B) actin heads will bind to myosin. C) active sites on the myosin are exposed. D) tropomyosin moves into the groove between the helical actin strands. E) myosin shortens.
D
4) Nerves and blood vessels that service the muscle fibers are located in the connective tissues of the A) sarcolemma. B) myofibrils. C) sarcomere. D) perimysium. E) endomysium.
D
44) A resting muscle generates most of its ATP by A) the tricarboxylic acid cycle. B) hydrolysis of creatine phosphate. C) glycogenolysis. D) aerobic metabolism of fatty acids. E) anaerobic respiration.
D
46) During anaerobic glycolysis A) pyruvic acid is produced. B) ATP is produced. C) oxygen is not consumed. D) all of the above E) B and C only
D
51) During the recovery period the body's need for oxygen is increased because A) the individual is panting. B) the muscles are not producing ATP. C) the liver requires more oxygen to produce lactic acid. D) additional oxygen is required to restore energy reserves consumed during exercise. E) muscle cells are producing energy anaerobically.
D
54) Muscular force can be adjusted to match different loads by A) recruiting more motor units B) varying the frequency of action potentials in motor neurons C) recruiting larger motor units D) A, B, and C E) None of the abovemuscle contraction is all-or-none.
D
67) Which of the following is not a type of motor unit? A) redfast twitch B) redslow twitch C) whitefast twitch D) whiteslow twitch E) All of these are well known.
D
72) Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber A) lengthens. B) strengthens. C) weakens. D) shortens. E) not enough information to say
D
75) Which statement about excitation-contraction coupling is incorrect? A) Tropomyosin moves to expose myosin binding sites on actin. B) Troponin binds calcium ion and signals tropomyosin to move. C) Calcium ion is released from the sarcoplasmic reticulum. D) Calcium ion is released from the transverse tubule. E) Relaxation requires uptake of calcium ion by the sarcoplasmic reticulum.
D
81) Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass? A) thyroid hormone B) epinephrine C) calcitonin D) testosterone E) parathyroid hormone
D
84) 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 A band during contraction. C) the I band + H band distance is constant during contraction. D) decreased width of the H band during contraction. E) increased width of the I band during contraction.
D
1) Which of the following is a recognized function of skeletal muscle? A) maintain posture B) maintain body temperature C) produce movement D) guard body entrances and exits E) all of the above
E
102) What is released from the structure labeled "9"? A) acetylcholine B) sarcoplasm C) acetylcholinesterase D) protein E) calcium ions
E
104) Where would calcium ion be predominately found? A) 1 B) 2 C) 4 D) 8 E) 9
E
105) What physiological process occurs in the structure labeled "7"? A) the sliding filament theory B) release of protein into the muscle fiber C) activity of acetylcholinesterase D) release of neurotransmitter E) conduction of the action potential into the cell interior
E
108) Which structure actively pumps calcium ions out of the sarcoplasm to produce relaxation? A) 2 B) 1 C) 3 D) 7 E) 6
E
109) Which of the following are found in the structure labeled "3"? A) titin B) actin C) tropomyosin D) myosin E) all of the above
E
110) Identify the structure where ATP is produced. A) 3 B) 6 C) 7 D) 2 E) 1
E
111) Where is ATP is consumed? A) 1 B) 6 C) 2 D) 3 E) 3 and 6
E
12) Which of the following best describes the term sarcoplasmic reticulum? A) protein that accounts for elasticity of resting muscle B) repeating unit of striated myofibrils C) largely made of myosin molecules D) thin filaments are anchored here E) storage and release site for calcium ions
E
18) The region of the sarcomere that always contains thin filaments is the A) A band. B) H band. C) M line. D) Z line. E) I band.
E
19) The area in the center of the A band that contains no thin filaments is the A) zone of overlap. B) I band. C) Z line. D) M line. E) H band.
E
21) Which of the following best describes the term titin? A) storage site for calcium ions B) largely made of myosin molecules C) thin filaments are anchored here D) repeating unit of striated myofibrils E) protein that accounts for elasticity of resting muscle
E
25) At rest, the tropomyosin molecule is held in place by A) myosin molecules. B) calcium ions. C) actin molecules. D) ATP molecules. E) troponin molecules.
E
29) The action potential is conducted into a skeletal muscle fiber by A) sarcoplasmic reticulum. B) neuromuscular junctions. C) motor end plates. D) triads. E) transverse tubules.
E
31) In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases A) sodium ions. B) hydrogen ions. C) potassium ions. D) acetylcholine. E) calcium ions.
E
36) Calcium ions are binding to troponin during the ________ of a muscle twitch. A) latent period B) contraction phase C) recovery phase D) relaxation phase E) both A and B
E
42) The increase in muscle tension that is produced by increasing the number of active motor units is called A) incomplete tetanus. B) treppe. C) complete tetanus. D) wave summation. E) recruitment.
E
48) After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs. A) treppe B) paralysis C) atrophy D) tetanus E) an oxygen debt
E
50) During the Cori cycle, in the liver A) lactic acid is produced from pyruvic acid. B) lactic acid is produced from glucose. C) lactic acid is shuffled to muscle cells. D) glucose is released from glycogen. E) glucose is produced from lactic acid.
E
52) Fast fibers A) have low resistance to fatigue. B) have many mitochondria. C) rely on aerobic metabolism. D) have twitches with a very brief contraction phase. E) both A and D
E
55) During activities requiring aerobic endurance A) glycogen and glycolysis are the primary sources of reserve energy. B) fatigue occurs in a few minutes. C) oxygen is not required. D) oxygen debts are common. E) most of the muscle's energy is produced in mitochondria.
E
57) Which of the following statements is (are) true regarding human muscles? A) Slow fibers are abundant in the back muscles. B) Eye muscles are composed entirely of fast fibers. C) Most have both slow and fast fibers. D) Slow fibers are abundant in the calf muscles. E) All of the above.
E
69) Compared to a "typical" body cell, skeletal muscle cells are A) filled with crystalline 3-D arrays of fibrous proteins. B) multinucleate. C) larger than normal cells. D) capable of rapid shortening against a load. E) all of the above
E
70) 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
71) When a skeletal muscle fiber contracts, A) the Z lines get closer together. B) the width of the A band remains constant. C) the zones of overlap get larger. D) the H bands and I bands get smaller. E) all of the above
E
73) Which statement about the microscopic anatomy of skeletal muscle fibers is true? A) Muscle fibers are continuous from tendon to tendon. B) Tubular extensions of the sarcolemma penetrate the fiber transversely. C) Cross striations result from the lateral alignment of thick and thin filaments. D) Each fiber has many nuclei. E) All are true.
E
76) Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell. A) 25 B) 70 C) 50 D) 100 E) 95
E
80) When contraction occurs, A) the H bands get smaller. B) the I bands get smaller. C) the Z lines move closer together. D) the width of the A band remains constant. E) all of the above
E
82) Because skeletal muscle contractions demand large quantities of ATP, skeletal muscles have A) a rich nerve supply. B) a rich blood supply. C) abundant mitochondria. D) A, B, and C E) both B and C
E
83) In rigor mortis A) cross-bridge cycling is absent. B) the myosin heads are attached to actin. C) ATP is depleted. D) muscles are inextensible. E) all of the above
E
85) When myosin cross-bridges bind to the active sites on actin, A) the sarcomere resists stretching. B) they pivot toward the M line. C) ADP is released. D) both A and B E) A, B, and C
E
88) 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) depolarization. B) treppe. C) oxygen debt. D) tetany. E) rigor mortis.
E
89) 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 cause spastic paralysis (muscles are contracted and unable to relax). C) It would produce muscle weakness. D) It would have little effect on skeletal muscles. E) It would cause flaccid paralysis (muscles are relaxed and unable to contract).
E
90) When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes A) less permeable to potassium ions. B) less permeable to sodium ions. C) repolarized. D) more permeable to calcium ions. E) more permeable to sodium ions.
E
96) Which of these would lead to increased oxygen consumption? A) increased muscle activity B) increased aerobic respiration by muscle cells C) increased conversion of lactic acid to glucose D) increased heat production E) all of the above
E
97) How would an elevated level of thyroid hormone in the body affect skeletal muscles? A) It would stimulate hypertrophy. B) It would cause an increase in muscle mass. C) It would decrease heat production by muscle tissue. D) It would stimulate atrophy. E) It would stimulate energy use and heat production.
E
129) A thin filament is constructed from actin, tropomyosin, troponin, and nebulin.
FALSE
132) Many visceral smooth muscle cells lack motor neuron innervation. How are their contractions coordinated and controlled
Gap junctions interconnect visceral smooth muscle fibers. An action potential that begins in one will spread to its surrounding neighbors. The action potential can be triggered by stretching, hormones, chemical changes, or stimulation at a myoneural junction on a distant smooth muscle cell.
134) 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.
117) ________ are stem cells located between the endomysium and sarcolemma that function in the repair of damaged muscle tissue.
Satellite cells
128) Glucose breakdown through glycolysis and mitochondrial activity provides the ATP needed to power muscular contractions.
TRUE
133) 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?
This is a case of competition between acetylcholine and the antibody. To make the patient's acetylcholine more effective, a drug that inhibits acetylcholinesterase would slow the breakdown of his acetylcholine, relieving some of the weakness. An acetylcholine blocker would be worse than doing nothing.
130) 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.
125) An ________ can be described as a broad tendinous sheet.
aponeurosis
121) The sequence of processes that links the action potential to contraction is called ________.
excitation-contraction coupling
118) Communication between axons and muscle fibers occurs at specialized synapses called ________.
neuromuscular junctions
120) The structural theory that explains how a muscle fiber contracts is called the ________.
sliding filament theory
126) An infection by the bacterium Clostridium tetani can cause the disease called ________.
tetanus
127) A muscle produces its highest tension when in complete ________.
tetanus
119) The complex of a transverse tubule and two adjacent terminal cisternae is known as a ________.
triad
124) A single contraction-relaxation cycle in a muscle fiber produces a ________.
twitch
