Question 1

The cell bodies of Betz cells are found in the
A) premotor cortex.
B) primary motor cortex.
C) supplementary motor cortex.
D) cerebellum.
E) basal ganglia.

Accepted Answer

Betz cells are large pyramidal neurons found in the primary motor cortex, specifically in layer V.

Question 2

The motor units of the thumb,fingers,and face contain the
A) fewest muscle fibers.
B) most muscle fibers.
C) fewest motor neurons.
D) most motor neurons.
E) most extensors.

Accepted Answer

The thumb, fingers, and face require fine motor control and precision movements, so their motor units contain the fewest muscle fibers. This allows for more precise control and finer movements.

Question 3

The axons of Betz cells are part of the
A) dorsolateral corticospinal tract.
B) dorsolateral corticorubrospinal tract.
C) anterolateral pathway.
D) ventromedial cortico-brainstem-spinal tract.
E) ventromedial corticospinal tract.

Accepted Answer

The Betz cells, also known as pyramidal cells of layer V in the primary motor cortex, send their axons down through the internal capsule and into the spinal cord where they form the dorsolateral corticospinal tract. This tract is responsible for controlling voluntary movement of the limbs, fingers, and toes.

Question 4

The descending pathway illustrated here is the

A) dorsolateral corticorubrospinal tract.
B) dorsolateral corticospinal tract.
C) ventromedial corticospinal tract.
D) ventromedial cortico-brainstem-spinal tract.
E) none of the above

Accepted Answer

The illustration depicts the pathway of the dorsolateral corticospinal tract, which originates in the primary motor cortex and travels through the posterior limb of the internal capsule, the cerebral peduncles, and the lateral column of the spinal cord. This tract is responsible for the voluntary control of skilled movements of the extremities, and is one of the most important descending pathways in the human nervous system.

Question 5

In general,the dorsolateral corticospinal tract controls the muscles of the
A) thighs.
B) body core.
C) hands and feet.
D) proximal limbs.
E) legs.

Accepted Answer

The dorsolateral corticospinal tract, also known as the lateral corticospinal tract, is responsible for controlling voluntary movement of the limbs, particularly the hands and feet. Therefore, choice C is the best option as it specifically mentions both hands and feet.

Question 6

Which of the following brain stem structures receives direct sensory information about balance?
A) cerebellum
B) reticular formation
C) vestibular nucleus
D) tectum
E) red nucleus

Accepted Answer

The vestibular nucleus is responsible for receiving direct sensory information about balance from the inner ear. The cerebellum is primarily responsible for coordinating movement and balance, but it does not directly receive sensory information about balance. The reticular formation, tectum, and red nucleus are involved in various functions such as regulation of sleep and arousal, visual and auditory processing, and motor control, but they are not specifically involved in balance.

Question 7

In contrast to the descending dorsolateral motor pathways,the ventromedial pathways
A) control the trunk.
B) are more diffuse.
C) are more strictly contralateral.
D) all of the above
E) both A and B

Accepted Answer

The ventromedial pathways control the trunk and are more diffuse, so option A and B are correct. There is no mention of the strict contralaterality in the ventromedial pathways, so option C is incorrect. Therefore, the best choice is E, which includes both A and B.

Question 8

In general,the ventromedial descending motor tracts control the muscles of the
A) thumbs.
B) fingers.
C) trunk.
D) toes.
E) face.

Accepted Answer

The ventromedial descending motor tracts, such as the vestibulospinal tract and the reticulospinal tract, are responsible for controlling the muscles of the trunk. These tracts help to maintain balance and posture, as well as coordinate movements of the limbs and head with the movement of the body. While they may also contribute to control of the face, toes, fingers, and thumbs, the primary role of the ventromedial tracts is trunk control. Therefore, the best choice is C.

Question 9

When a motor neuron fires,all of the muscle fibers of its motor
A) unit contract together.
B) pool contract together.
C) segment contract together.
D) equivalence contract together.
E) feedback contract together.

Accepted Answer

When a motor neuron fires, all of the muscle fibers of its motor unit contract together. This is known as the all-or-none principle, meaning that all the fibers in the motor unit will either be activated or not activated based on the firing of the neuron.

Question 10

In neuroanatomy,"rubro" refers to the
A) substantia nigra.
B) vestibular system.
C) caudate.
D) red nucleus.
E) cerebellum.

Accepted Answer

In neuroanatomy, "rubro" refers to the red nucleus, which is located in the mesencephalon (midbrain) and plays a role in motor coordination and arm movement. Therefore, the best choice is D.

Question 11

In contrast to the axons of the descending dorsolateral motor pathways,individual axons of the ventromedial pathways often terminate
A) directly on motor neurons.
B) in two or more segments.
C) on both sides of the spinal cord.
D) both A and B
E) both B and C

Accepted Answer

Individual axons of the ventromedial pathways often terminate in two or more segments and on both sides of the spinal cord, allowing for the coordination of postural and gross limb movements across multiple spinal levels and bilaterally.

Question 12

Most axons of the dorsolateral corticorubrospinal tract synapse on
A) muscles of the fingers and thumb.
B) muscles of the hands and wrists.
C) interneurons of the spinal gray matter that in turn synapse on motor neurons that project to the distal muscles of the arms and legs.
D) motor neurons that project to the fingers.
E) Betz cells.

Accepted Answer

The dorsolateral corticorubrospinal tract is involved in voluntary movements of the limbs. Most of its axons synapse on interneurons in the spinal gray matter, which then synapse on motor neurons that project to the distal muscles of the arms and legs.

Question 13

Only primates and a few other species,such as hamsters and raccoons,have cortical neurons that synapse directly on
A) muscles.
B) muscles of the fingers and thumb.
C) motor neurons that project to the muscles of the fingers and thumb.
D) spinal interneurons.
E) targets in the PNS.

Accepted Answer

Cortical neurons that synapse directly on motor neurons in the spinal cord that project to the muscles of the fingers and thumb are called corticomotoneuronal cells (CMNs). Only primates and a few other species, such as hamsters and raccoons, have these cells, which allow for fine motor control and dexterity in the fingers and hands.

Question 14

In the classic experiments of Lawrence and Kuypers,the descending motor tracts of monkeys were transected.The results of these experiments suggest that the function of the ventromedial pathways is the control of
A) posture.
B) movements of the body core and associated arm movements.
C) reaching for objects.
D) all of the above
E) both A and B

Accepted Answer

The results of Lawrence and Kuypers' experiments suggested that the ventromedial pathways are responsible for the control of posture and movements of the body core and associated arm movements. Therefore, the best choice is E, as it includes both A and B. The experiments did not suggest that the ventromedial pathways are responsible for reaching for objects, so option C can be eliminated. Since options A and B are mentioned in the explanation, option D can also be eliminated.

Question 15

In one classic experiment,monkeys had difficulty letting go of food after their
A) dorsolateral corticorubrospinal tracts were transected.
B) dorsolateral corticospinal tracts were transected.
C) ventromedial corticospinal tracts were transected.
D) cerebellum was lesioned.
E) basal ganglia were lesioned.

Accepted Answer

The dorsolateral corticospinal tracts are responsible for voluntary movement and their transection can affect the ability to release objects voluntarily. Therefore, the monkey's difficulty letting go of food suggests damage to these tracts.

Question 16

In contrast to the ventromedial corticospinal tract,before descending to the spinal cord,the ventromedial cortico-brainstem-spinal tract interacts with the
A) tectum.
B) reticular formation.
C) vestibular nuclei.
D) all of the above
E) none of the above

Accepted Answer

The ventromedial cortico-brainstem-spinal tract interacts with multiple brainstem structures before descending to the spinal cord. These include the tectum (involved in visual and auditory processing), the reticular formation (involved in motor control and arousal), and the vestibular nuclei (involved in balance and eye movement). Therefore, the best choice is D, which includes all of the above brainstem structures.

Question 17

In which of the following structures would the motor units likely be the smallest?
A) finger
B) leg
C) arm
D) foot
E) back

Accepted Answer

Smaller muscles are typically found in areas that require more precise and fine movements such as the fingers. Larger muscles are found in areas that require greater force generation such as the legs and back.

Question 18

Which midbrain structure receives visual and auditory information about spatial location?
A) tectum
B) cerebellum
C) basal ganglia
D) tegmentum
E) vestibular nucleus

Accepted Answer

The tectum is responsible for receiving visual and auditory information about spatial location, specifically the superior colliculus for visual and inferior colliculus for auditory. The other options listed do not primarily receive this type of sensory information.

Question 19

In the classic transection experiments of Lawrence and Kuypers,monkeys with all their dorsolateral motor pathways transected sat with their arms hanging limply by their sides.However,these same monkeys had no difficulty
A) picking up pieces of food and then releasing them.
B) using their arms for standing, walking, and climbing.
C) reaching for moving objects.
D) moving their fingers independently.
E) all of the above

Accepted Answer

Monkeys with transected dorsolateral motor pathways could still use their arms for postural adjustments necessary for standing, walking, and climbing, indicating these functions rely on different neural pathways.

Question 20

The decussation in the medullary pyramids is part of the
A) dorsolateral corticospinal tract.
B) dorsolateral corticorubrospinal tract.
C) ventromedial corticospinal tract.
D) ventromedial cortico-brainstem-spinal tract.
E) both C and D

Accepted Answer

The decussation in the medullary pyramids is part of the dorsolateral corticospinal tract, which carries motor signals from the cortex to the spinal cord. Option B is incorrect because the corticorubrospinal tract does not pass through the pyramids, but rather the red nucleus. Options C and D are both incorrect as they do not involve the medullary pyramids.

Quiz 8: The Sensorimotor System

The cell bodies of Betz cells are found in the

The motor units of the thumb,fingers,and face contain the

The axons of Betz cells are part of the

The descending pathway illustrated here is the

In general,the dorsolateral corticospinal tract controls the muscles of the

Which of the following brain stem structures receives direct sensory information about balance?

In contrast to the descending dorsolateral motor pathways,the ventromedial pathways

In general,the ventromedial descending motor tracts control the muscles of the

When a motor neuron fires,all of the muscle fibers of its motor

In neuroanatomy,"rubro" refers to the

In contrast to the axons of the descending dorsolateral motor pathways,individual axons of the ventromedial pathways often terminate

Most axons of the dorsolateral corticorubrospinal tract synapse on

Only primates and a few other species,such as hamsters and raccoons,have cortical neurons that synapse directly on

In the classic experiments of Lawrence and Kuypers,the descending motor tracts of monkeys were transected.The results of these experiments suggest that the function of the ventromedial pathways is the control of

In one classic experiment,monkeys had difficulty letting go of food after their

In contrast to the ventromedial corticospinal tract,before descending to the spinal cord,the ventromedial cortico-brainstem-spinal tract interacts with the

In which of the following structures would the motor units likely be the smallest?

Which midbrain structure receives visual and auditory information about spatial location?

In the classic transection experiments of Lawrence and Kuypers,monkeys with all their dorsolateral motor pathways transected sat with their arms hanging limply by their sides.However,these same monkeys had no difficulty

The decussation in the medullary pyramids is part of the