Deck 9: Organization of Motor Function

Question 1

The phasic Ia stretch reflex:

A)Has a polysynaptic reflex arc.
B)Acts to maintain a constant level of tension in the muscle.
C)Is initiated by a receptor that lies in series with the extrafusal fibers.
D)Has its sensitivity controlled by the gamma motor neuron system.

Answer 1

D

Question 2

According to the size principle:

A)Large α motor neurons are recruited before small ones.
B)Large and small α motor neurons are recruited simultaneously.
C)α and $\gamma$ motor neurons are activated simultaneously during a movement.
D)α motor neurons are activated before $\gamma$ motor neurons during a movement.
E)Small motor neurons are more excitable than are large motor neurons.

Answer 2

Small motor neurons are more excitable than are large motor neurons.

Question 3

A stimulus applied to the surface of the cerebellar cortex activates a beam of parallel fibers.This produces:

A)A wave of inhibited Purkinje cells in line with the parallel fiber beam.
B)Waves of excited Purkinje cells that flank the parallel fiber beam.
C)A wave of excited basket and stellate cells in line with the parallel fiber beam.
D)Waves of excited basket and stellate cells that flank the parallel fiber beam.
E)Complex spikes in Purkinje cells in line with the parallel fiber beam.

Answer 3

C

Question 4

Upper motor neuron (or pyramidal tract)syndrome is:

A)Characterized by the permanent loss of the stretch reflexes.
B)Fully expressed when only the corticospinal tract is interrupted.
C)Characterized by a lasting decrease in muscle tone.
D)Characterized by Babinski's sign and the appearance of other pathological reflexes.
E)Fully expressed after damage to the vestibular nuclei.

Question 5

With a person standing upright,head rotation to the right causes:

A)Activation of hair cells in the left horizontal canal and right abducens nucleus.
B)Activation of hair cells in the right horizontal canal and right abducens nucleus.
C)Activation of hair cells in the left horizontal canal and left abducens nucleus.
D)Activation of hair cells in the right horizontal canal and left abducens nucleus.
E)A vertical nystagmus

Question 6

Damage to which structure would produce an extensor rigidity that would not be significantly altered by section of the dorsal roots?

A)Lateral vestibular nucleus.
B)Anterior vermal region of the cerebellar cortex.
C)Medullary reticular formation (nucleus gigantocellularis).
D)Cortical afferent pathways to the pontine and medullary reticular formation.
E)Cortex of the cerebellar hemisphere.

Question 7

A monkey makes arm movements while you record the activity of a cell in primary motor cortex in a cortical column related to arm muscles.What is probably true about the cell's activity?

A)It is linearly related to movement direction and thus can predict the direction of the upcoming movement.
B)It does not vary with movement direction.
C)It always increases during the movement.
D)It is nonlinearly related to movement direction and does not predict the specific direction of the upcoming movement.

Question 8

In the motor map of the primary motor cortex:

A)Each muscle is represented by a single cortical column.
B)Each muscle is represented by multiple columns within a single continuous region.
C)The number of cortical columns representing a muscle is proportional to the mass of the muscle.
D)The amount of territory representing a muscle is correlated with the degree of fine control over movements made using that muscle.
E)Columns controlling different muscles are randomly intermixed.

Question 9

Dopamine's action in the caudate and putamen will _____ activity in the globus pallidus internal (GPi)as a result of _______.

A)Decrease; activation of the direct pathway and inhibition of the indirect pathway
B)Decrease; inhibition of the direct pathway and activation of the indirect pathway
C)Increase; activation of the direct pathway and inhibition of the indirect pathway
D)Increase; inhibition of the direct pathway and activation of the indirect pathway
E)Decrease; inhibition of both direct and indirect pathways

Question 10

Intrafusal muscle fibers but not extrafusal fibers:

A)Receive only sensory innervation.
B)Are innervated by only one motor neuron.
C)Contain an equatorial region with little to no contractile protein.
D)Run the length of the muscle.