BISC306H Exam 2
100. Which type of skeletal muscle fiber typically has a smaller diameter? A. Type I B. Type II
a
12. What is the definition of a "motor unit?" A. a single motor neuron plus all the muscle fibers it innervates B. a single muscle fiber plus all of the motor neurons that innervate it C. all of the motor neurons supplying a single muscle D. a pair of antagonistic muscles E. all of the muscles that affect the movement of any given joint
a
15. Which of the following does not describe the highest hierarchical level of motor control? A. It creates a "motor program" that uses afferent information to generate a pattern of neural activity required to carry out a given action. B. It involves brain regions that include the sensorimotor and cortical association areas. C. It sends signals along "command neurons" to parts of the brain that make up the middle level of the motor control hierarchy. D. It involves brain regions that function in memory, emotions, and motivation. E. It initiates consciously-planned movements.
a
16. What is the importance of reciprocal innervation in muscular reflexes? A. It prevents simultaneous activity of antagonistic muscle groups that would impede limb movement. B. It ensures that limbs on the contralateral side of the body perform the same movements as those on the ipsilateral side. C. It maintains signaling along afferent neurons from stretch receptors, even when a muscle shortens rapidly. D. It prevents excessive force on a muscle from resulting in tearing of fibers, or damage to the tendon. E. It recruits synergistic muscles to come to the aid of a muscle that help it generate force and limb motion.
a
17. Myasthenia gravis is an autoimmune disease in which the immune system gradually destroys the receptors for acetylcholine at the neuromuscular junction. Which of the following drugs might initially be useful in treating the symptoms of this disease? A. a drug that inhibits acetylcholinesterase B. a drug that inhibits release of acetylcholine C. curare D. atropine (a muscarinic acetylcholine receptor antagonist) E. a nicotinic acetylcholine receptor antagonist
a
23. The optimal length (Lo) of a skeletal muscle cell is: A. the length at which the muscle can generate its maximum tetanic tension. B. the shortest length the muscle can achieve while attached to bone, because the amount of overlap between thick and thin filaments is maximal then. C. generally the length attained when the joint it crosses is fully extended. D. the only length at which any tension can be generated by the muscle cell. E. the length at which thin filaments from opposite sides of a sarcomere overlap.
a
24. In the first few seconds of skeletal muscle contraction, what is the main mechanism by which ATP is replenished? A. Energy and phosphate are transferred from creatine phosphate to ADP. B. Oxidative phosphorylation rapidly generates ATP from glucose. C. Glycolysis produces ATP from glycogen. D. Oxidation of fatty acids into ATP occurs in the mitochondria. E. Myoglobin catalysis produces ATP.
a
26. Why does breathing continue to be rapid and deep for a time after heavy exercise? A. Extra oxygen is needed to eliminate lactic acid and restore muscle creatine phosphate and glucose concentrations. B. The respiratory system is slow to increase and decrease its function before and after exercise, which is why it takes awhile for breathing to slow down. C. Lactic acid that builds up during heavy exercise must be exhaled into the air, so heavy breathing must continue for awhile after exercise to eliminate it. D. The ATP level in muscle cells falls drastically during heavy exercise, and extra oxygen is needed to restore it. E. The extra ventilation is not needed to replenish energy stores in muscle fibers, but rather simply to restore the blood pH to normal after the production of excess lactic acid during the exercise.
a
27. The corticospinal pathways: A. are descending motor pathways. B. begin in the cortex of the cerebellum. C. consist of many interneurons linked synaptically. D. are composed of alpha motor neurons. E. bring sensory information from the spinal cord to the somatosensory region of the cerebral cortex.
a
29. What is the definition of "muscle tone?" A. the resistance of muscle to continuous passive stretch B. the sound made by a muscle at rest C. the maximum contraction strength that a muscle is capable of D. the tension in a muscle that is only due to the passive resistance of elastic structures E. the average length of the muscle fibers in a given motor unit
a
3. What is the best description of how a given muscle fiber can be inhibited from contracting? A. Inhibitory inputs from local reflexes and descending pathways prevent the fiber's motor neuron from firing action potentials. B. Descending inputs from brainstem components of the middle level of the motor control hierarchy make inhibitory synapses onto the muscle fibers. C. Contractions in an antagonistic muscle's fibers are stronger than the given muscle's contractions. D. Golgi tendon organs send afferent neurons directly to muscle fibers that attach to them and release inhibitory neurotransmitter. E. Interneurons in the local spinal cord region send axons to the muscle fiber's neuromuscular junction, where they impose presynaptic inhibition.
a
33. Which of these would increase the tension generated in a skeletal muscle? A. increasing the frequency of firing in alpha motor neurons innervating the muscle B. stretching the muscle to very long lengths C. resting the muscle for several weeks D. switching off fast-glycolytic motor units and activating an equal number of slow-oxidative motor units E. increasing the amplitude of action potentials in the alpha motor neurons that innervate the muscle
a
34. Which of the following statements regarding whole-muscle contraction is TRUE? A. The order of recruitment of motor units in a muscle is such that the last units recruited are those that fatigue most readily. B. The order of recruitment of motor units in a muscle is such that the first units recruited generate the most tension C. Motor units whose motor neurons have large-diameter cell bodies are recruited first, while motor units with smaller-diameter motor neurons are only activated as the level of activation in the spinal cord increases. D. The order of motor unit recruitment is independent of the size of the alpha motor neuron that innervates them. E. Recruitment of one fast-glycolytic motor unit provides a smaller increment in whole-muscle tension than recruitment of one slow-oxidative motor unit.
a
35. John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a marathon runner who specializes in long, steady runs. Compared to Jim, John is likely to have: A. legs with a larger diameter. B. legs with a smaller diameter. C. hypertrophy of type I muscle fibers. D. a higher density of capillaries in his legs. E. lower concentrations of glycolytic enzymes in his leg muscles.
a
39. Which of these is a major difference between smooth muscle and skeletal muscle? A. Myosin is the main regulatory protein in smooth muscle. B. Myosin is the main regulatory protein in skeletal muscle. C. Skeletal muscle usually exhibits spontaneous activity, while smooth muscle cannot contract spontaneously. D. Only skeletal muscle requires increased calcium ion concentration in the cytosol for contraction. E. Only skeletal muscle has both actin and myosin.
a
43. Which of the following is FALSE regarding single-unit smooth-muscle cells? A. They have an individual neuron innervating of each individual smooth-muscle cell. B. They have many gap junctions between cells. C. They may have pacemaker activity. D. They may respond to stretch by contracting. E. They exhibit tone.
a
44. Multiunit smooth-muscle cells A. generally have individual innervation of each cell. B. have many gap junctions between cells. C. respond to stretch by relaxing. D. can only be excited, and not inhibited. E. have abundant T-tubules.
a
6. Intrafusal muscle fibers: A. are found in muscle spindles. B. are innervated by alpha motor neurons. C. generate most of the tension in a skeletal muscle. D. fire continuously at a constant rate. E. are only found in extensor muscles.
a
8. Which best describes "rigor mortis?" A. Lack of ATP following death causes cross-bridges to remain tightly bound to actin. B. Lack of ATP following death causes calcium to remain in the cytosol, continuously stimulating cross-bridge cycling. C. Repeated, high-frequency action potentials to a skeletal muscle fiber causes sustained contraction following death. D. Following death, calcium-activated proteases degrade all proteins in skeletal muscle fibers, making muscles limp. E. Build-up of K+ in T-tubules causes constant, tetanic contractions of skeletal muscles that last for about 12 hours following death.
a
9. What is responsible for the phenomenon in skeletal muscle known as muscle tone? A. the passive elastic properties of muscles and joints and some degree of alpha motor neuron activity B. spontaneous entry of calcium into the cytosol and the background phosphorylation of cross-bridges C. depletion of ATP in some individual muscle fibers, and the inability for cross-bridges to detach D. cross-bridges that continuously cycle, even in the absence of cytosolic Ca2+ E. a build-up of K+ in the T-tubules and resulting depolarization of the sarcolemma
a
92. Abundant mitochondria is typical of which type of skeletal muscle fibers? A. Type I B. Type II
a
93. Abundant myoglobin is typical of which type of skeletal muscle fibers? A. Type I B. Type II
a
96. Which type of skeletal muscle fibers is generally recruited first? A. Type I B. Type II
a
1. Which best describes a "myofibril?" A. It is a single skeletal-muscle cell. B. It is a cylindrical cellular organelle composed of myofilaments. C. It is a hollow membranous structure that stores calcium. D. It is composed of a single type of protein and forms cross-bridges. E. It is a fibrous junction between a muscle cell and a tendon.
b
10. Which of the following normally occurs when a doctor's reflex hammer taps a patient's patellar tendon? A. Alpha motor neurons stimulate contraction of intrafusal fibers in extensor muscles. B. Alpha motor neurons stimulate contraction of extrafusal fibers in extensor muscles. C. Alpha motor neurons that innervate ipsilateral flexor muscles are stimulated. D. Inhibitory interneurons reduce action potential firing in alpha motor neurons to extrafusal fibers of extensor muscles. E. Golgi tendon organs in the patellar tendon stimulate the contraction of extrafusal fibers of extensor muscles.
b
12. Which best describes an event that occurs as part of the crossed-extensor reflex? A. It is initiated by a painful stimulus in the ipsilateral limb. B. It stimulates contraction of the contralateral extensor and inhibits contraction of the contralateral flexor. C. It is initiated by stretch in the ipsilateral extensor muscle. D. Inhibitory interneurons are activated, which synapse onto contralateral extensor muscles. E. Monosynaptic excitatory stimulation of ipsilateral extensor muscles occurs.
b
14. Which of the following would occur if you touched a hot object with your right hand? A. A stretch reflex would be triggered that would cause contraction of extensor muscles in the right arm. B. A withdrawal reflex would be triggered by nociceptors that would stimulate contraction of flexor muscles in the right arm. C. Reflex mechanisms would stimulate contraction of the extensor muscles of the right arm. D. A withdrawal reflex would be triggered by stretch receptors that would inhibit contraction of extensor muscles of the right arm. E. Nociceptors send pain information to the cerebral cortex, and descending activation of alpha motor neurons to extensor muscles would make you withdraw your right hand from the object.
b
2. What protein is the principle component of skeletal muscle thick filaments? A. actin B. myosin C. troponin D. calmodulin E. tropomyosin
b
21. What is the best description of a tetanic contraction in a skeletal muscle cell? A. A single action potential in the motor neuron causes a sustained contraction. B. Multiple action potentials in the motor neuron cause a sustained contraction. C. The action potential in the muscle cell is prolonged to last as long as the contraction. D. Repeated action potentials from the motor neuron summate into a sustained depolarization of the motor end plate, causing a sustained contraction. E. A very large amplitude action potential in the motor neuron causes a very strong contraction in the skeletal muscle cell.
b
22. Which best describes the specific cause of Parkinson disease? A. enhanced sensitivity of cholinergic receptors to acetylcholine B. reduced ability of neurons in the substantia nigra to release dopamine C. failure of serotonin receptors to bind with these neurohormones D. hyperactivity of metabolic enzymes that degrade dopamine E. natural tendency of basal nuclei to follow a daily recurring, oscillating cycle of rising and falling norepinephrine release
b
27. Which of the following statements regarding myosin in skeletal muscle is TRUE? A. Myosin cross-bridge heads contain two binding sites, one for actin and one for tropomyosin. B. Myosin is an ATPase. C. The rate of ATP hydrolysis by myosin is the same in all types of skeletal muscle. D. All of the myosin cross-bridge heads in a thick filament are oriented and rotate in the same direction. E. Troponin covers the binding site on myosin molecules until Ca2+ binds to troponin to remove it from its blocking position.
b
28. Compared to type I (slow oxidative) skeletal muscle fibers, how are type II b (fast-glycolytic) skeletal-muscle fibers different? A. Type II b fibers have more abundant mitochondria. B. Type II b fibers fatigue more readily. C. Type II b fibers have more abundant myoglobin. D. Type II b fibers are smaller in diameter. E. Type II b motor units contain fewer fibers per alpha motor neuron.
b
30. Afferent pathways of the postural reflexes come mainly from: A. the cerebellum. B. the eyes, the vestibular apparatus, and the receptors involved in proprioception. C. muscle spindles and temperature receptors. D. nociceptors and chemoreceptors. E. the somatosensory cortex.
b
36. John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a marathon runner who specializes in long, steady runs. Compared to John's muscles, how are Jim's most likely to differ? A. Jim's muscles will have more glycogen stored in his type II b muscle fibers. B. Jim's muscles will have more mitochondria in his type I and II a muscle fibers. C. Jim's muscles will have less myoglobin in his type I muscle fibers. D. Jim's type II b fibers will be larger in diameter. E. Jim will have a greater proportion of type II muscle fibers and a lower proportion of type I fibers than John.
b
47. The prolonged electrical depolarization of cardiac muscle cells that occurs during contraction is due primarily to the persistent influx of what ion? A. sodium B. calcium C. nitrate D. chloride E. potassium
b
5. Stretch reflexes: A. occur only in the legs. B. inhibit antagonistic muscles. C. mediate flexor activation and withdrawal from a painful stimulus. D. are initiated by stimulation of Golgi tendon organs. E. are initiated by stretching of extrafusal muscle fibers.
b
51. Myasthenia gravis is a collection of muscle disorders that cause muscle fatigue and weakness. What is the major mechanism? A. overproduction of acetylcholinesterase B. autoimmune destruction of nicotinic acetylcholine receptors C. demyelination of axons in motor pathways D. autoimmune destruction of L-type Ca2+ channels. E. a tumor that overproduces acetylcholine
b
6. Binding of ________ to myosin permits cross-bridge _____________ between actin and myosin in skeletal muscle cells. A. ATP; attachment B. ATP; detachment C. calcium; attachment D. calcium; detachment E. actin; detachment
b
7. Which occurs FIRST as a result of ATP binding to myosin? A. cross-bridge heads are cocked into an "energized" state B. actin dissociates from from myosin C. Ca2+ is released from the sarcoplasmic reticulum D. actin binds to myosin E. cross-bridges rotate, sliding past the thin filament
b
94. A large diameter is typical of which type of skeletal muscle fibers? A. Type I B. Type II
b
95. Fast myosin ATPase activity is typical of which type of skeletal muscle fibers? A. Type I B. Type II
b
97. Which type of skeletal muscle fibers fatigues most quickly? A. Type I B. Type II
b
98. Which type of skeletal muscle fiber typically has the fewest mitochondria? A. Type I B. Type II
b
99. Which type of skeletal muscle fiber typically has less myoglobin? A. Type I B. Type II
b
1. Which of the following statements is true with regard to the motor control hierarchy? A. The highest level of the hierarchy of motor control includes the frontal lobe cortex, the primary motor cortex, muscle sensory receptors, and the basal ganglia. B. The highest level of the hierarchy of motor control is composed entirely of areas of cerebral cortex, and its main purpose is to create a conscious plan to move that depends on the initial position of the parts of the body in space. C. Neurons of the middle level of the hierarchy integrate afferent information with signals from higher center command neurons to create a motor program--a pattern of neural activity required to properly perform a desired movement. D. The local level of the motor control hierarchy includes the premotor and primary motor regions of the cerebral cortex, as well as the alpha motor neurons and muscle fibers themselves. E. Reflexes that include local-level receptors and muscle fibers cannot occur without input from the higher centers of the motor control hierarchy.
c
11. Which of the following statements is TRUE regarding skeletal-muscle contraction? A. Only one cross-bridge cycle can occur when the [Ca2+] is elevated in the cytosol; in order to undergo a second cycle, [Ca2+] must be sequestered in the sarcoplasmic reticulum and released again. B. ATP hydrolysis products must be removed from myosin before it can bind to actin. C. Binding of myosin to actin takes place when [Ca2+] increases in the cytosol. D. A single twitch in skeletal muscle lasts the same length of time as the action potential that causes it. E. The powerstroke of the cross-bridge cycle occurs simultaneously with ATP being hydrolyzed into ADP and Pi.
c
13. What is the function of the transverse tubules in a skeletal-muscle fiber? A. They store the calcium ions that are the main source of activation for the cross-bridge cycle. B. They form the Z lines that mark the end of each sarcomere. C. They allow action potentials to propagate deep into the center of skeletal muscle cells. D. They manufacture and store ATP. E. They run in parallel with the myofibrils, and have abundant Ca2+-ATPase proteins for pumping Ca2+ back into the sarcoplasmic reticulum.
c
15. Which of the following statements regarding the motor end plate of a skeletal-muscle fiber is TRUE? A. Muscarinic receptors in the end plate are activated by binding to acetylcholine. B. Temporal summation of multiple end plate potentials is required in order to trigger an action potential in the muscle-fiber membrane. C. Acetylcholinesterase in the end plate membrane catalyzes the breakdown of acetylcholine. D. Sympathetic nerve fibers terminate on skeletal muscle fibers at the motor end plate. E. The motor end-plate under the axon terminal contains a large number of voltage-gated Na+ channels.
c
17. What is the principle defect in Parkinson disease? A. There is a loss of neurons in the reticular activating system that secrete acetylcholine. B. There is a demyelination of alpha motor neurons important for posture and balance. C. Neurons of the substantia nigra degenerate and there is reduced delivery of dopamine to the basal ganglia. D. Autoimmune destruction occurs in neurons in the motor regions of the cerebral cortex. E. Damage to neurons of the cerebellum reduces the coordination of muscle movements.
c
18. Which of these occurs during an isometric contraction of a skeletal muscle? A. The I bands shorten and the A bands stay the same length. B. The thick and thin filaments slide past each other. C. Sarcomere length does not change. D. The A bands shorten and the I bands stay the same length. E. Cross-bridges lock onto actin, similar to what occurs in rigor mortis.
c
19. During an isometric twitch in a skeletal muscle: A. tension generated by the muscle always exceeds the load on the muscle. B. tetanus occurs. C. sarcomeres do not significantly shorten. D. the whole muscle shortens. E. the load on the muscle is always greater than the tension generated.
c
19. Which is a symptom of Parkinson disease? A. flaccid paralysis B. intention tremor C. resting tremor D. memory loss E. loss of proprioception
c
25. When a muscle has been repeatedly contracting at a moderate intensity for an extended period of time (more than a few minutes), what is the primary source of ATP? A. transfer of energy and phosphate from creatine phosphate to ADP B. glycolysis C. oxidative phosphorylation D. breakdown of myosin E. uptake of ATP from the blood plasma
c
25. Which of the following symptoms is common following damage to the cerebellum? A. flaccid paralysis B. violent, uncontrolled body movements called chorea C. intention tremors D. resting tremors E. spastic paralysis
c
29. Which of the following statements about different kinds of skeletal-muscle fibers is TRUE? A. Slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers. B. Fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers. C. A fast-glycolytic fiber can generate greater tension than a slow-oxidative fiber. D. Fast-glycolytic fibers and slow-oxidative fibers are innervated by alpha motor neurons of the same diameter. E. To generate ATP, fast-glycolytic fibers depend mainly on oxidative phosphorylation while slow-oxidative fibers depend mainly on glycolysis.
c
3. During concentric isotonic contraction of a skeletal-muscle fiber, which of these occurs? A. sarcomeres lengthen B. A bands shorten C. I bands shorten D. A bands lengthen E. thin filaments shorten
c
30. Fast-glycolytic muscle fibers differ from slow-oxidative fibers in that: A. fast-glycolytic fibers rely on creatine phosphate as an ATP source for the first few seconds of contraction but slow-oxidative fibers do not. B. fast-glycolytic fibers have a smaller diameter than slow-oxidative fibers. C. fast-oxidative fibers can generate greater maximal tension than slow-oxidative fibers. D. fast-oxidative fibers generate less lactic acid than slow-oxidative fibers.
c
38. Which of the following statements is FALSE? A. Synaptic input onto skeletal muscle cells is always excitatory, whereas inputs to smooth muscle cells may be either excitatory or inhibitory. B. A single smooth-muscle cell may be innervated by both a sympathetic neuron and a parasympathetic neuron. C. Contractile activity of smooth-muscle cells does not normally require Ca2+. D. In the absence of any neural input, skeletal muscle cannot generate tension. E. Ca2+ that activates contraction of smooth muscles can come from either the ECF or from the sarcoplasmic reticulum.
c
4. Which of the following statements regarding contraction of a skeletal-muscle fiber is TRUE? A. Thick filaments shorten when muscle cells contract. B. Some contractions occur without cross-bridge activation. C. Contracting muscle fibers do not always shorten. D. Contraction does not always require the occurrence of an action potential. E. Contraction only occurs following summation of action potentials from many motor neurons.
c
40. Which is a TRUE statement about smooth muscle? A. Smooth muscle is striated. B. Smooth muscle does not have thick and thin filaments. C. Smooth muscle does not use troponin-tropomyosin to regulate cross-bridge activity. D. Changes in cytosolic calcium do not regulate cross-bridge activity in smooth muscle. E. The myosin in smooth muscle requires phosphorylation before it can bind to ATP.
c
48. Which membrane protein transport process plays an important role in terminating the contraction of cardiac muscle? A. Ca 2+-ATPase pumps move Ca2+ from the T-tubule back into the sarcoplasmic reticulum. B. Na+/K+-ATPase pumps move Na+ back into the cytosol and K+ back into the T-tubule lumen. C. Ca2+-ATPase pumps move Ca2+ from the cytosol back into the sarcoplasmic reticulum. D. Na+/Ca2+-exchangers move Na+ out of the cytosol in exchange for Ca2+ movement into the sarcoplasmic reticulum. E. Na+/K+-ATPase pumps move Na+ and K+ back out of the cell.
c
49. Which best describes a role of L-type Ca2+ channels in cardiac muscle cells? A. They function exactly the same in cardiac muscle cells as they do in skeletal muscle. B. They are directly responsible for making cardiac muscle fatigue resistant. C. They are responsible for preventing tetanic contractions. D. They cause the absolute refractory period to be very brief. E. They act as non-conducting voltage sensors that mediate excitation-contraction coupling.
c
5. In skeletal muscle cells, calcium initiates contraction by binding to: A. tropomyosin. B. actin. C. troponin. D. myosin. E. the thick filament.
c
7. Which is TRUE about the muscle fibers found in a muscle spindle? A. They are not true muscle fibers because they cannot contract. B. They are innervated by alpha motor neurons. C. They function to maintain tension on spindle receptors. D. When stimulated to fire, they always inhibit flexor muscles muscles. E. Their contraction is stimulated by alpha motor neurons and inhibited by gamma motor neurons.
c
10. The removal of calcium ions from the cytosol of skeletal muscle causes A. the myosin binding sites on actin to be uncovered by tropomyosin. B. tropomyosin to change conformation and thereby move troponin molecules over cross-bridge binding sites. C. troponin to change conformation and thereby expose cross-bridge binding sites. D. the myosin binding sites on actin to be covered by tropomyosin. E. None of the choices are correct.
d
11. The flexor (withdrawal) reflex A. has a monosynaptic component. B. is initiated by stretching muscle spindle fibers. C. is initiated by stimulation of the Golgi tendon organ. D. stimulates contraction of the ipsilateral flexor muscle and inhibits contraction of the ipsilateral extensor muscle. E. stimulates contraction of the contralateral flexor muscle and inhibits contraction of the contralateral extensor muscle.
d
13. What is the function of Golgi tendon organs? A. They detect stretch within tendons and inhibit the activation of alpha motor neurons to extrafusal muscle fibers in antagonistic muscles. B. They detect painful stimuli within tendons and inhibit gamma motor neurons to intrafusal muscle fibers in muscles attached to those tendons. C. They detect the angle of joints, and thus provide proprioceptive inputs about the position of the limbs in space. D. They detect stretch within tendons and inhibit the activation of alpha motor neurons to extrafusal muscle fibers in the muscle attached to those tendons. E. They stimulate the ends of intrafusal muscle fibers, ensuring that sensory information about muscle length is provided, even when a muscle shortens rapidly.
d
14. An action potential in the motor end plate rapidly spreads to the interior regions of a muscle cell by means of the: A. Z lines. B. sarcoplasmic reticulum. C. H zone. D. transverse tubules. E. pores in the plasma membrane.
d
16. How does the chemical curare affect skeletal muscle function? A. It activates an autoimmune disease that destroys myelin. B. It blocks the action of acetylcholinesterase at the neuromuscular junction. C. It is a muscarinic acetylcholine receptor antagonist that blocks synaptic transmission at the neuromuscular junction. D. It is a nicotinic acetylcholine antagonist that blocks synaptic transmission at the neuromuscular junction. E. It locks ligand-gated channels in the open state, leading to spastic contractions of muscle.
d
18. What is the function of the basal nuclei in normal motor control? A. They provide a perceptual awareness related to specific sensory inputs from the eyes, nose, and mouth. B. They provide a general perceptual awareness associated with somatosensory inputs from the skin, muscles, and joints. C. They provide a sense of the cause and effect relationships between muscle actions and the consequences of taking these actions - before executing them. D. They participate in a looping neuronal circuit through which motor impulses are sent to facilitate or suppress movements. E. They form an initial intention to move, such as when you decide to pick up an object.
d
2. According to the hierarchy of motor control, A. the highest level of control consists entirely of neurons in the primary motor region of the cerebral cortex. B. the middle level of control does not involve any areas of the cerebral cortex. C. the local level of control includes the cerebellum and basal ganglia. D. structures in the middle level receive information from both the higher and the local levels of the hierarchy. E. afferent information from skin, joint, and muscle receptors cannot modify a movement once it has been initiated by a motor program from the middle level of the hierarchy.
d
20. Which of the following statements regarding skeletal-muscle contraction is true? A. During a lengthening contraction, the tension exerted by the muscle exceeds the load on the muscle. B. In every isotonic muscle contraction, the length of the muscle remains constant. C. During every muscle contraction, muscle fibers change length. D. During every muscle contraction, tension is developed in the muscle. E. Cross-bridges cycle faster during isometric contractions than during isotonic contractions.
d
21. What is the main reason a patient with Parkinson disease cannot be treated with dopamine? A. Acetylcholine is the main neurotransmitter that is deficient. B. Injecting dopamine only makes the substantia nigra down-regulate its own production of dopamine. C. Dopamine is highly addictive, creating a dependence in the patient that is worse than Parkinson disease. D. Dopamine cannot cross the blood-brain barrier, and it has too many systemic side effects. E. Dopamine is a protein that is digested in the stomach before it can enter a person's circulation.
d
28. Which of the following is not true of corticospinal fibers? A. They may synapse directly on alpha motor neurons. B. They may synapse directly on gamma motor neurons. C. They may synapse directly on interneurons. D. They are collectively sometimes called the extrapyramidal system. E. They may synapse with afferent neurons in ascending pathways.
d
31. When a walking person lifts one foot off of the ground, which of these happens? A. The body leans so that the center of gravity shifts over the foot that is lifted off of the ground. B. The body only accelerates forward, so the center of gravity remains directy between the two feet. C. The body accelerates forward, but the center of gravity shifts over the foot that is lifted off the ground. D. The body leans so that the center of gravity shifts over the foot that is on the ground. E. The center of mass is left behind by the acceleration of the body, so the body must lean forward to compensate.
d
32. Which of the following statements regarding skeletal muscle is TRUE? A. Skeletal muscle fibers have pacemaker activity. B. Skeletal muscle fibers are joined together by gap junctions. C. A given skeletal muscle fiber will contract when excitatory nervous stimuli sufficiently exceed inhibitory nervous stimuli at the motor end plate D. A given skeletal muscle fiber will contract if excitatory synaptic inputs sufficiently exceed inhibitory synaptic inputs on the motor neuron that innervates that fiber and the motor neuron fires an action potential. E. Skeletal muscle contraction is inhibited by inhibitory motor neurons that synapse onto skeletal muscle fibers.
d
37. If a biopsy of the quadriceps (thigh extensor) muscles were taken from gold medal-winning speed skaters in the 4 events below, which would most likely have the SMALLEST percentage of type I muscle fibers? A. 10,000 meters B. 5,000 meters C. 1,000 meters D. 500 meters
d
41. Which is a TRUE statement about excitation-contraction coupling? A. In skeletal muscle cells, it requires the influx of extracellular calcium ion. B. In smooth muscle cells, it must be preceded by an action potential in the cell membrane. C. In all kinds of muscle it requires the entry of calcium from the extracellular fluid. D. Calcium-induced calcium-release plays a role in cardiac muscle cells, as well as in some smooth muscle cells. E. In skeletal muscle cells, EC coupling begins when an action potential propagates along the sarcoplasmic reticulum membrane.
d
42. Which of the following statements regarding contraction in skeletal and smooth muscle is TRUE? A. In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding directly to myosin. B. In skeletal muscle, calcium ions bind to a regulatory protein on thin filaments; in smooth muscle, calcium ions bind to a regulatory protein on thick filaments. C. In skeletal muscle, calcium initiates contraction by binding to myosin light-chain kinase, while in smooth muscle calcium initiates contraction by binding directly to tropomyosin. D. In skeletal muscle, calcium initiates contraction by binding to troponin, while in smooth muscle calcium initiates contraction by binding to calmodulin. E. All of the choices are true.
d
9. Rigor mortis is caused by: A. buildup of lactic acid. B. lack of Ca2+. C. depletion of glycogen. D. lack of ATP. E. deficient acetylcholine receptors.
d
20. What are the symptoms of patients with cerebellar disease? A. They cannot initiate movements, but will sit as though frozen for extended periods of time. B. They have resting tremors, in which the head or limbs will continuously oscillate when no movement is intended. C. They lose the ability to comprehend language, although they are still fully capable of speaking words. D. All reflexes governing unconscious reactions to muscle stretch, muscle force, and nociceptor input are lost. E. They cannot perform limb or eye movements smoothly, showing intention tremors that increase as a movement nears its final destination.
e
22. How is the length of a skeletal muscle cell related to the force it can generate? A. The tension in a skeletal muscle cell is greatest when contractions occur at either very short or very long lengths. B. Skeletal muscle cells generate the same amount of force, regardless of their length. C. The shorter a skeletal muscle cell is when it begins to contract, the stronger the force generation will be. D. The longer a skeletal muscle cell is when it begins to contract, the stronger the force generation will be. E. Skeletal muscle cells generate the most force when the contraction occurs at an intermediate length.
e
23. Why do people with Parkinson disease experience resting tremors? A. damage to the cerebellum alternately activates agonist/antagonist muscle pairs B. excess glutamate is released in the premotor areas of the motor cortex C. dopamine-secreting tumors directly activate alpha motor neurons D. acetylcholinesterase at neuromusclular junctions is inactivated E. dopamine release in the substantia nigra suppresses descending motor pathways
e
24. Which is TRUE about the function of the cerebellum? A. It helps to coordinate body movements. B. It is important in maintaining posture. C. It receives input from sensory pathways. D. It stores the memory of motor movements that involve several joints. E. All of the choices are correct.
e
26. Which of the following statements about control of body movement is FALSE? A. The corticospinal motor pathways control most fine, discrete muscle activity. B. The brain stem pathways control postural and most other coordinated body movements. C. The cerebellum fine-tunes ongoing movement and helps to coordinate movements. D. The corticobulbar pathways begin in the sensorimotor cortex and end in the brainstem. E. The corticospinal tracts from the right sensorimotor cortex control movements of limbs on the right side of the body.
e
31. Which of the following is NOT a determinant of whole-muscle tension? A. the number of muscle fibers contracting B. the tension produced by each contracting fiber C. the numbers of motor units recruited D. the frequency of motor neuron stimulation E. the proportion of the muscle fibers within each motor unit that are contracting at any given time
e
4. Which is NOT true about reflexes initiated by muscle spindle activation? A. They have a monosynaptic component. B. They result in activation of alpha motor neurons. C. They result in activation of extrafusal muscle fibers. D. The "knee jerk" reflex is an example. E. They inhibit the activation of muscles that are stretched.
e
45. Which of the following does NOT correctly describe cardiac muscle cells? A. They are arranged in layers surrounding hollow cavities in the heart. B. They are much shorter than skeletal muscle fibers, and generally have a single nucleus. C. Their membranes are depolarized initially by the influx of sodium ions. D. They depolarize prior to contraction. E. They can contract in the absence of external calcium.
e
46. Which of the following choices lists a correct sequence of events following the depolarization of transverse tubules in excitation-contraction coupling in cardiac muscle? A. calcium release into cytosol, calcium ion influx through sarcolemma, actin and myosin attach, thin filaments slide toward the middle of sarcomeres B. actin and myosin attach, thin filaments slide toward the middle of sarcomeres, calcium release into cytosol C. calcium release into cytosol, actin and myosin attach, calcium ion influx through sarcolemma, thin myofilaments slide toward the middle of sarcomeres D. calcium release into cytosol, actin and myosin attach, thin filaments slide toward the middle of sarcomeres, calcium ion influx through sarcolemma E. calcium ion influx through sarcolemma, calcium release into cytosol, actin and myosin attach, thin myofilaments slide toward the middle of sarcomeres
e
50. Which dietary supplement is most likely to contribute to greater skeletal muscle ATP availability in the first few seconds of skeletal muscle contraction? A. fatty acids B. sports drinks with electrolytes and mineral spirits C. sugar D. protein E. creatine
e
8. What occurs when gamma motor neurons to a muscle are activated? A. The muscle spindle goes slack. B. The contractile ends of intrafusal fibers elongate. C. The muscle lengthens. D. Extrafusal muscle fibers within that muscle are inhibited from contracting. E. Action potential firing increases in afferent neurons from the muscle spindles.
e
34. Once a planned movement is under way, it is usually carried out with no further modifications until it is finished. True False
f
38. Information from the muscle spindle stretch receptors is not conveyed above the level of the spinal cord and thus does not reach consciousness. True False
f
40. Stimulation of a Golgi tendon organ causes a reflex contraction of the muscle whose tension the receptor is monitoring. True False
f
42. When a person steps on a tack with the left foot, flexor muscles on the right leg and extensor muscles on the left leg will be stimulated to contract. True False
f
43. The skeletal muscles of the body are represented in the primary motor cortex proportionately to their size. True False
f
45. The thalamus is an important relay station for feedback of information to the basal ganglia from the motor cortex. True False
f
47. In general, the brainstem descending pathways have greater influence over motor neurons controlling muscles involved in fine movements and the corticospinal pathways are more involved in the coordination of large muscle groups and postural muscles. True False
f
48. Crossed-extensor reflexes, but not stretch reflexes, are important postural reflexes. True False
f
50. Sensory neurons that are part of the stretch reflex synapse directly onto the motor neurons of antagonist muscles, and inhibit them. True False
f
54. The force-generating sites in a myofibril are the Z lines. True False
f
55. During skeletal-muscle contraction, the distance between the Z lines of a sarcomere decreases because of shortening of the filaments. True False
f
57. The step of the cross-bridge cycle that immediately follows the attachment of ATP to the myosin head is referred to as the "powerstroke." True False
f
59. Actin is an ATPase enzyme. True False
f
63. "Excitation-contraction coupling" refers to the binding of energized myosin to actin. True False
f
64. The site of Ca2+ storage in muscle cells is the lateral sacs of the transverse tubules. True False
f
65. Curare blocks neuromuscular transmission by preventing the release of neurotransmitters from the motor neuron. True False
f
66. Organophosphate "nerve gases" induce paralysis by blocking neural stimulation of the neuromuscular junctions, while botulinum toxin produces the same effect by inhibiting acetylcholinesterase. True False
f
67. The term "twitch" refers to the mechanical response of a muscle fiber during one cross-bridge cycle. True False
f
70. The latent period of an isotonic twitch is shorter than the latent period of an isometric twitch. True False
f
72. A skeletal muscle generates its greatest twitch tension when it is stretched to twice its resting length. True False
f
74. Characteristics of slow-oxidative fibers include numerous mitochondria, abundant myoglobin and large stores of glycogen. True False
f
75. The difference in color between white muscle and red muscle is accounted for by the greater abundance of glycogen in white muscle. True False
f
76. The fiber type intermediate between the two extremes of fast-glycolytic and slow-oxidative is slow-glycolytic. True False
f
78. In general, activating a slow-oxidative motor unit in a muscle will generate more tension than activating a fast-glycolytic motor unit. True False
f
79. Endurance exercise, such as long-distance swimming, causes a preferential increase in glycolytic enzymes and increased mass of the exercising muscles. True False
f
83. Flexor muscles generally pull on bone and decrease the angle at a joint, whereas extensor muscles push the bone to increase the angle. True False
f
84. The decrease in mass and strength of muscle as a result of damage to the nerves innervating the muscle is called disuse atrophy. True False
f
87. In smooth muscle cells that can produce action potentials, cell membrane depolarization usually opens voltage-sensitive sodium channels. True False
f
90. Multiunit smooth muscle is characterized by many gap junctions between cells. True False
f
91. In cardiac muscle cells the release of Ca2+ through L-type Ca2+ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca2+ necessary for excitation-contraction coupling. True False
f
32. The motor neuron pool of a skeletal muscle consists of the neurons of all of the motor units of that muscle. True False
t
33. Inhibitory input to motor neurons is as important for normal muscle function as excitatory input. True False
t
35. Practicing a movement allows for "fine tuning" the original program so that the movement can be executed with fewer corrections. True False
t
36. Afferent information about body movement is in part integrated at the level of the interneurons controlling the firing of motor neurons. True False
t
37. Afferent fibers from muscle spindle stretch receptors in a muscle make excitatory synaptic contact with motor neurons that innervate the extrafusal fibers of the same muscle. True False
t
39. During motor activity, alpha-gamma coactivation provides important information regarding muscle length to the higher motor control centers. True False
t
41. The activity of alpha motor neurons innervating an extensor muscle can be inhibited by activation of the Golgi tendon organs in the tendon that attaches that muscle to bone. True False
t
44. The primary motor cortex in the right side of the brain mainly controls the left half of the body. True False
t
46. One of the primary roles of the cerebellum is to compare a given program for movement with the actual movement as it occurs and to make adjustments in the movement and in the program. True False
t
49. Motor pathways extending from the central nervous system to muscle fibers are subject to control by both excitatory and inhibitory interneurons. True False
t
51. Motor neurons which innervate skeletal muscle fibers are subject to the summative effects of interneurons firing either excitatory, inhibitory, or both kinds of neurotransmitters simultaneously. True False
t
52. Skeletal muscles are made up of bundles of muscle fibers attached to bone by connective-tissue called tendons. True False
t
53. The name given to the repeating functional units that cause striations in a skeletal muscle myofibril is "sarcomere." True False
t
56. During concentric contractions of skeletal muscle, the I band and H zone shorten but the A band stays the same. True False
t
58. The energy for muscle contraction is provided indirectly by the hydrolysis of ATP. True False
t
60. The binding of ATP to myosin causes an allosteric change in myosin's actin-binding site such that the affinity of myosin for actin is decreased. True False
t
61. The phenomenon of rigor mortis demonstrates that myosin can remain bound to actin in the absence of additional ATP, but the bond cannot then be broken. True False
t
62. Binding of myosin to actin in skeletal muscle cells does not normally take place in the absence of Ca2+. True False
t
68. When the load on a skeletal muscle is less than the tension the muscle generates, a concentric isotonic contraction results. True False
t
69. During isometric contraction of a skeletal-muscle fiber, tension increases but the fiber length stays the same. True False
t
71. Sustained contraction and tension in a skeletal muscle is called tetanus. True False
t
73. Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP. True False
t
77. Muscles used for delicate, finely controlled movements have smaller motor units than muscles used for high power activities. True False
t
80. The larger the diameter of a skeletal-muscle fiber, the greater the tension it can generate. True False
t
81. Recruitment of different types of motor units in a muscle is one means of varying the amount of tension generated in that muscle. True False
t
82. The shortening velocity of a skeletal muscle fiber increases with decreasing load because the rate at which the cross-bridge cycle can occur increases with decreasing load. True False
t
85. A Ca2+-binding protein in smooth muscle is calmodulin. True False
t
86. The myosin in smooth muscle cells differs from that in skeletal muscle in that smooth muscle myosin requires phosphorylation before it can bind to actin. True False
t
88. Neuronal stimulation of skeletal muscle is always excitatory, whereas neuronal stimulation of smooth muscle may be excitatory or inhibitory. True False
t
89. Smooth muscle cells may contract in the absence of neuronal stimulation. True False
t
