Physio Ch. 12 MCQB Part 2

213) The calcium release channels in smooth muscle sarcoplasmic reticulum are a) IP3-receptor channels. b) ryanodine receptors. c) DHP receptors. d) caveolae. e) A and B

a) IP3-receptor channels. AND b) ryanodine receptors. e) A and B

181) The contraction cycle is triggered by the rise in __________ released from the SR. a) Ca2+ b) K+ c) Na+ d) A and B e) A, B, and C

a) Ca2+

178) In living muscle at rest (relaxed), which situation is most common? a) The myosin head is not attached to any molecule. b) The myosin head is attached to ADP and inorganic phosphate. c) The myosin head is strongly attached to G-actin. d) B and C e) None of the above

b) The myosin head is attached to ADP and inorganic phosphate.

211) In smooth muscle, what is the small protein chain that regulates contraction and relaxation? a) actin b) myosin light chain c) myosin heavy chain d) calcium e) none of the above

b) myosin light chain

171) The I band contains a) an area of overlapping filaments. b) thin filaments. c) thick filaments. d) all of the above e) none of the above

b) thin filaments.

204) Put these neurons and myofibers in order of recruitment from first to last. (1) highest threshold neurons (2) lowest threshold neurons (3) higher threshold neurons (4) fatigue resistant slow twitch fibers (5) fatigue resistant oxidative fast twitch fibers (6) glycolytic fast twitch fibers (a) 1, 4, 3, 5, 2, 6 (b) 2, 4, 3, 5, 1, 6 (c) 3, 4, 1, 6, 2, 5 (d) 2, 4, 6, 1, 3, 5 (e) 1, 6, 3, 5, 2, 4

(b) 2, 4, 3, 5, 1, 6

182) Put these events in the correct chronological sequence. (1) end plate potentials trigger action potentials (2) transverse tubules convey potentials into the interior of the cell (3) acetylcholine binds to receptors on the motor end plate (4) binding sites on actin are uncovered, allowing myosin to bind and carry out power strokes (5) Ca2+ is released from the sarcoplasmic reticulum (6) chemically regulated ion channels open, causing depolarization (7) Ca2+ ions bind to troponin-C, pulling on tropomyosin (a) 5, 3, 2, 1, 4, 7, 6 (b) 2, 4, 7, 6, 3, 1, 5 (c) 4, 1, 3, 7, 2, 6, 5 (d) 3, 6, 1, 2, 5, 7, 4 (e) 3, 6, 1, 5, 7, 2, 4

(d) 3, 6, 1, 2, 5, 7, 4

185) When comparing complete tetanus with unfused tetanus, which is true? a) In complete tetanus, maximum tension is developed. b) In complete tetanus, some relaxation occurs between stimuli. c) In complete tetanus, the muscle fiber is stimulated at a higher frequency. d) A and B e) A and C

a) In complete tetanus, maximum tension is developed. AND c) In complete tetanus, the muscle fiber is stimulated at a higher frequency. e) A and C

In the arm, the biceps brachii act as flexor whereas triceps brachii act as extensor. Which of the following statements is true? a) The biceps brachii would be the primary muscle responsible for movement of the hand and forearm towards the shoulder. b) The triceps brachii would be the primary muscle responsible for movement of the hand and forearm towards the shoulder. c) These muscles are an example of antagonistic muscle groups. d) A and B e) A and C

a) The biceps brachii would be the primary muscle responsible for movement of the hand and forearm towards the shoulder. AND c) These muscles are an example of antagonistic muscle groups. e) A and C

173) Which statement is true? a) The energy released by ATP hydrolysis produces the power stroke by swiveling the myosin head. b) Myosin is a motor protein that converts the chemical bond energy of GTP into the mechanical energy of motion. c) Each myosin molecule acts as an enzyme which both binds ATP and releases its energy. d) A and B e) A and C

a) The energy released by ATP hydrolysis produces the power stroke by swiveling the myosin head. AND c) Each myosin molecule acts as an enzyme which both binds ATP and releases its energy. e) A and C

174) Which statement is true? a) The sarcomere shortens, the two Z disks at each end move closer together, and the I band and H zone virtually disappear. b) The thin actin filaments slide along the thick myosin filaments as they move toward the M line in the center of the sarcomere. c) When a muscle contracts, myosin molecules coil up like springs to shorten the length. d) A and B e) A and C

a) The sarcomere shortens, the two Z disks at each end move closer together, and the I band and H zone virtually disappear. AND b) The thin actin filaments slide along the thick myosin filaments as they move toward the M line in the center of the sarcomere. d) A and B

180) Why does rigor mortis occur after death? a) There is no ATP available to bind to myosin. b) Body temperature drops. c) Connective tissue around muscle fascicles hardens. d) Myosin is tightly bound to troponin. e) A and D

a) There is no ATP available to bind to myosin.

172) Which of the following statements is true about titin? a) Titin stabilizes the position of the contractile filaments. b) Titin returns stretched muscle to their resting length. c) Titin is helped by actin. d) all of the above. e) A and B

a) Titin stabilizes the position of the contractile filaments. AND b) Titin returns stretched muscle to their resting length. e) A and B

214) Which statement about smooth muscle contraction is FALSE? a) Troponin plays the same role as in skeletal muscle. b) It uses actin and myosin cross-bridges to create force. c) It can occur without a change in membrane potential. d) Ca2+ initiates contraction.

a) Troponin plays the same role as in skeletal muscle.

If a somatic motor neuron fires an action potential, then a) acetylcholine is released from the axon terminal. b) a skeletal muscle is triggered to contract. c) the response may be inhibition of the muscle cell. d) all of the above e) A and B

a) acetylcholine is released from the axon terminal. AND b) a skeletal muscle is triggered to contract. e) A and B

Smooth muscles a) are the primary muscle of internal organs and tubes. b) include cardiac muscles. c) lack cross-bands of striated muscles. d) A and B e) A and C

a) are the primary muscle of internal organs and tubes. AND c) lack cross-bands of striated muscles. e) A and C

202) The force generated by a single muscle fiber a) can be increased by increasing the frequency of action potentials. b) is always the same. c) can be increased due to summation. d) A and B e) A and C

a) can be increased by increasing the frequency of action potentials. AND c) can be increased due to summation. e) A and C

208) Compared to skeletal muscle, smooth muscle __________. a) is slower to contract in response to a stimulus b) sustains contractions longer without fatigue c) develops tension more rapidly and relaxes more rapidly d) A and B e) A and C

a) is slower to contract in response to a stimulus AND b) sustains contractions longer without fatigue d) A and B

197) Central fatigue a) may be related to changes in the brain related to changes in the pH of the blood. b) includes feeling irritable. c) may precede physiological muscle fatigue. d) A and B e) A and C

a) may be related to changes in the brain related to changes in the pH of the blood. AND c) may precede physiological muscle fatigue. e) A and C

189) When acetylcholine is released into the neuromuscular junction, __________. a) muscle action potentials are triggered, which lead to activation of the contraction cycle b) the muscle membrane depolarizes, creating an end-plate potential (EPP) c) it binds to receptors which only allow Na+ ions to cross the sarcolemma d) all of the above e) A and B

a) muscle action potentials are triggered, which lead to activation of the contraction cycle AND b) the muscle membrane depolarizes, creating an end-plate potential (EPP) e) A and B

Skeletal muscles are said to be striated because of a repeating pattern of light and dark bands. One repeating unit of the entire pattern of bands correspond to a(n) __________. a) sarcomere b) myofilament c) actin molecule d) crossbridge e) Z disk

a) sarcomere

212) In smooth muscle, Ca2+ for contraction comes from a) sarcoplasmic reticulum. b) extracellular fluid. c) mitochondria. d) A and B e) A and C

a) sarcoplasmic reticulum. AND b) extracellular fluid. d) A and B

201) A factor or factors determining the speed and duration of a twitch in various types of fibers is the speed of the a) speed of ATP hydrolysis. b) removal of Ca2+ ions from the cytosol. c) movement of K+ across their membranes. d) A and B e) A and C

a) speed of ATP hydrolysis. AND b) removal of Ca2+ ions from the cytosol. d) A and B

188) Excitation-contraction coupling a) starts at the neuromuscular junction. b) involves the opening of sarcoplasmic reticulum calcium release channels also known as ryanodine receptors. c) is initiated by acetylcholine release from sympathetic neurons. d) all of the above e) A and B

a) starts at the neuromuscular junction. AND b) involves the opening of sarcoplasmic reticulum calcium release channels also known as ryanodine receptors. e) A and B

177) Each myosin head has a) the ability to swivel using power derived from ATP hydrolysis. b) a binding site for an cAMP molecule. c) a binding site for an troponin molecule. d) A and B e) A, B, and C

a) the ability to swivel using power derived from ATP hydrolysis.

200) Within a single fiber, the tension developed during a twitch can vary because a) the amount of overlap of thick and thin filaments must be sufficient to allow cross-bridge formation. b) the motor neuron releases differing amounts of neurotransmitter into the synapse. c) stimuli vary in intensity and duration. d) stimuli vary in intensity. e) all of the above

a) the amount of overlap of thick and thin filaments must be sufficient to allow cross-bridge formation.

199) Summation in a single muscle fiber may mean that a) the fiber stays contracted longer. b) the fiber increases the force of the contraction. c) the fiber increases the frequency of contraction. d) A and B e) A and C

a) the fiber stays contracted longer. AND b) the fiber increases the force of the contraction. d) A and B

Nicotinic receptors a)bind ACh and open monovalent cation channels. b)are identical throughout the nervous system. c)are found on skeletal muscles at the neuromuscular junction. d)A and B e)A and C

a)bind ACh and open monovalent cation channels. AND c)are found on skeletal muscles at the neuromuscular junction. e)A and C

196) Fatigue during extended submaximal exertion is known to be associated mainly with a) depletion of ATP stores. b) depletion of glycogen stores. c) depletion of Na+ stores. d) A and B e) A, B, and C

b) depletion of glycogen stores.

193) Metabolism of __________ is the fastest way for cells to increase their supply of ATP in order to meet the ATP demands of heavy exercise. a) proteins b) glucose c) fatty acids d) A and B e) A, B, and C

b) glucose

165) The purpose of transverse tubules __________. a) is to conduct ATP molecules out of the mitochondria throughout the sarcoplasm b) is to rapidly conduct action potentials to the interior of the muscle fiber c) is to ensure a supply of glycogen throughout the muscle sarcoplasm d) is to ensure a supply of Ca2+ ions through the muscle fiber e) all of these are correct

b) is to rapidly conduct action potentials to the interior of the muscle fiber

218) An important difference between single-unit and multiunit smooth muscle is a) closely controlled individual fibers in single-unit smooth muscle to allow fine control and graded contractions by selective activation. b) numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet. c) longer actin and myosin filaments in multiunit smooth muscle, which allow coordination of contraction. d) the ability of single-unit fibers to change into multiunit fibers when advantageous. e) all of the above

b) numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet.

187) Excitation-contraction coupling refers to __________. a) acetylcholine opening ion channels b) the chemical and electrical events that trigger the mechanical events in a muscle fiber c) the enzymatic removal of acetylcholine from the synapse which can then allow relaxation to occur d) the arrival of acetylcholine at the neuromuscular junction due to its exocytosis from the axon terminal e) B and D

b) the chemical and electrical events that trigger the mechanical events in a muscle fiber

176) The power stroke begins when __________. a) the ATP is hydrolyzed by the myosin head b) the inorganic phosphate is released from the myosin c) the actin is attached to the myosin head d) the actin is released by the myosin head e) A and B

b) the inorganic phosphate is released from the myosin

198) Within a single fiber, the tension developed during a twitch depends on a) the duration of the stimulus. b) the length of the sarcomeres prior to contraction. c) the amount of neurotransmitter in the synapse. d) the force required to move the relevant joint. e) the magnitude of the stimulus.

b) the length of the sarcomeres prior to contraction.

175) As ATP binds to the myosin head at the beginning of a muscle contraction cycle, __________. a) the myosin head tightens its bond to actin b) the myosin head detaches from actin c) ATP does not bind to the myosin head d) the myosin head initiates binding with actin e) none of the above

b) the myosin head detaches from actin

_________ is made of multiple globular molecules polymerized to form long chains or filaments. a) Tropomyosin b) Troponin c) Actin d) Titin e) Myosin

c) Actin

Identify the FALSE statement. a) Skeletal muscle contraction is not directly influenced by hormones. b) Smooth muscle is often present in the walls of hollow organs. c) Skeletal muscle contraction is always under conscious control. d) There are only three types of muscle tissue in the human body. e) Skeletal muscle is always striated.

c) Skeletal muscle contraction is always under conscious control.

Which statement does NOT apply to the skeletal muscles? a) They are attached to the bones of the skeleton, causing movement. b) They control "voluntary" body movement. c) They are the only muscles classified as striated. d) all of the above. e) none of the above

c) They are the only muscles classified as striated.

169) When the myosin heads are loosely bound to the actin filaments, the _________ span the space between the parallel thick and thin filaments. a) tropomyosin molecules b) nebulin molecules c) crossbridges d) sarcomeres e) A and D

c) crossbridges

190) The backup energy source for muscles is __________. a) creatine phosphokinase (CPK) b) creatine kinase c) phosphocreatine d) ATP e) all of the above

c) phosphocreatine

209) Most _________ muscle is found in the walls of hollow organs and blood vessels. a) cardiac b) skeletal c) smooth d) A and B e) A, B and C

c) smooth

186) The period of time during which the sarcomeres return to their resting length is referred to as a) the depolarization period. b) the repolarization period. c) the relaxation phase. d) the refractory period. e) the latent period.

c) the relaxation phase.

170) The H zone contains a) an area of overlapping filaments. b) thin filaments. c) thick filaments. d) all of the above e) none of the above

c) thick filaments.

206) In muscles used for fine actions, such as controlling eye movement or use of the hand, a motor unit will have _________ muscle fibers when compared to a motor unit in muscles used for power and strength. a) approximately the same numbers of b) hundreds more c) very few d) is impossible to predict

c) very few

Which statement is incorrect? a) T-tubules allow action potentials to be conveyed rapidly from the surface to the interior of the muscle fiber. b) The sarcoplasm of the muscle contains glycogen granules and mitochondria. c) Muscle fibers are the largest cells in the body. d) A skeletal muscle fiber has one or two nuclei. e) None of the statements are incorrect.

d) A skeletal muscle fiber has one or two nuclei.

191) Muscles require _________ constantly, they can only store enough of it for about eight twitches. a) glycogen b) calcium c) oxygen d) ATP e) blood

d) ATP

_________ of muscle fibers are bundles of contractile and elastic proteins that contract. a) Terminal cisternae b) Transverse tubules c) Sarcoplasm d) Myofibrils e) Fascicles

d) Myofibrils

203) Each of these statements is true, except one. Identify the exception. a) With endurance training, the metabolic characteristics of muscle fibers can be changed and enhanced. b) A power muscle, such as in the calf of the leg, may have 2000 muscle fibers in one motor unit. c) All muscle fibers in a single motor unit are of the same fiber type. d) The entire skeletal muscle contracts in an all-or-none manner. e) Each skeletal motor unit contracts in an all-or-none manner.

d) The entire skeletal muscle contracts in an all-or-none manner.

184) Regulation of cross-bridge formation is accomplished by __________. a) calcium ions b) tropomyosin c) troponin d) all of the above e) A and B

d) all of the above

215) Dephosphorylation of the myosin light chain in the smooth muscle is a) a step in the smooth muscle relaxation. b) accomplished with the aid of the enzyme myosin phosphatase. c) a decrease in myosin ATPase activity. d) all of the above e) A and C

d) all of the above

216) When comparing the energy usage of smooth muscle to skeletal muscle, which is/are true? a) Smooth muscle resists fatigue due to anaerobic metabolism. b) Smooth muscle has low oxygen consumption rates. c) Smooth muscle uses less energy to create the same force. d) all of the above e) A and B

d) all of the above

192) The condition that results when a muscle is no longer able to generate or sustain the expected power output is called __________. a) refraction b) tired c) twitch d) fatigue e) tetany

d) fatigue

The thick filament of the myofibril is composed of approximately 250 _________ molecules. a) troponin b) tropomyosin c) titin d) myosin e) actin

d) myosin

205) A motor unit consists of __________. a) one nerve and the body region it controls b) one nerve and the skeletal muscles it is attached to c) one motor neuron collateral and one muscle fiber it controls d) one motor neuron and all the muscle fibers it controls e) all of the above

d) one motor neuron and all the muscle fibers it controls

217) One of the major differences among skeletal muscle fiber types is in their resistance to fatigue. The fibers with the most endurance rely on _________ for energy. a) ketone body degradation b) lactic acid accumulation c) anaerobic glycolysis d) oxidative phosphorylation e) all of the above

d) oxidative phosphorylation

210) Smooth muscle cells lack which protein(s)? a) actin b) myosin c) calmodulin d) troponin e) C and D

d) troponin

207) Asynchronous recruitment __________. a) helps avoid fatigue during sustained muscle contractions b) makes an entire muscle seem to contract smoothly c) refers to different motor units taking turns maintaining muscle tension d) A and B e) A, B and C

e) A, B and C

194) The onset of fatigue in a muscle cell is influenced by a) the intensity and duration of the contractile activity. b) the fitness level of the individual. c) the use of aerobic or anaerobic metabolism. d) A and B e) A, B, and C

e) A, B, and C

179) At the conclusion of the power stroke, a) inorganic phosphate has been released from the myosin. b) ADP is released from the myosin head. c) actin has been moved toward the M line. d) the myosin head is tightly bound to actin. e) All of the above

e) All of the above

Which statement about cardiac muscle is false? a) It is classified as a striated muscle. b) It can contract spontaneously. c) It is controlled involuntarily. d) It is only found in the heart. e) It is easily fatigued.

e) It is easily fatigued.

195) Fatigue may be associated with __________. a) accumulation of H+ from lactic acid b) a shift in K+ levels which decrease Ca2+ release c) depletion of glycogen d) increased levels of inorganic phosphate (Pi) e) all of the above

e) all of the above

183) The brief period of time between the end of the action potential in the muscle and the beginning of contraction is referred to as a) the relaxation phase. b) the depolarization period. c) the repolarization period. d) the refractory period. e) the latent period.

e) the latent period.