Deck 10: Control of Body Movement

Question 1

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.

Answer 1

A

Question 2

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.

Answer 2

B

Question 3

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

Answer 3

A

Question 4

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.

Question 5

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.

Question 6

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.

Question 7

Which is a symptom of Parkinson disease?

A)flaccid paralysis
B)intention tremor
C)resting tremor
D)memory loss
E)loss of proprioception

Question 8

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.

Question 9

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.

Question 10

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.

Question 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.

Question 12

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.

Question 13

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.

Question 14

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.

Question 15

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.

Question 16

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.

Question 17

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.

Question 18

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.

Question 19

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.

Question 20

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.

Question 21

Inhibitory input to motor neurons is as important for normal muscle function as excitatory input.

Question 22

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.

Question 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

Question 24

Once a planned movement is under way,it is usually carried out with no further modifications until it is finished.

Question 25

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.

Question 26

During motor activity,alpha-gamma coactivation provides important information regarding muscle length to the higher motor control centers.

Question 27

Practicing a movement allows for "fine tuning" the original program so that the movement can be executed with fewer corrections.

Question 28

The motor neuron pool of a skeletal muscle consists of the neurons of all of the motor units of that muscle.

Question 29

Afferent information about body movement is in part integrated at the level of the interneurons controlling the firing of motor neurons.

Question 30

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.

Question 31

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

Question 32

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.

Question 33

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.

Question 34

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.

Question 35

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

Question 36

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

Question 37

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.

Question 38

Stimulation of a Golgi tendon organ causes a reflex contraction of the muscle whose tension the receptor is monitoring.

Question 39

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.

Question 40

Information from the muscle spindle stretch receptors is not conveyed above the level of the spinal cord and thus does not reach consciousness.

Question 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.

Question 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.

Question 43

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.

Question 44

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.

Question 45

The thalamus is an important relay station for feedback of information to the basal ganglia from the motor cortex.

Question 46

The skeletal muscles of the body are represented in the primary motor cortex proportionately to their size.

Question 47

Motor pathways extending from the central nervous system to muscle fibers are subject to control by both excitatory and inhibitory interneurons.

Question 48

Crossed-extensor reflexes,but not stretch reflexes,are important postural reflexes.

Question 49

Sensory neurons that are part of the stretch reflex synapse directly onto the motor neurons of antagonist muscles,and inhibit them.

Question 50

The primary motor cortex in the right side of the brain mainly controls the left half of the body.

Question 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.