PRACTICE QUESTIONS

1. A motor neuron pool located most laterally in the ventral horn of the spinal cord is most likely to operate a muscle controlling movement of the:

a. Proximal limb

b. Neck

c.

d. Abdomen

2. Which of the following is true regarding decerebrate rigidity?

a. It can result from severe forebrain disease.

b. Disruption of the cortical control of medullary reticulospinal neurons is a major contributor to the condition.

c. It can result in a fixed, rigid, hobbyhorse-like posture

io te quadruped.

d. Removal of normal inhibition to some of the antigravity muscles contributes to the condition.

e. All the above are true.

3. Which of the following descending brainstem motor pathways controls distal limb musculature associated with skilled movement?

a. Vestibulospinal tract

b. Rubrospinal tract

c. Reticulospinal tract

d. Teclospinal tract

e. All the above play a major role in such control.

4. The corticospinal (pyramidal) tract, in general, initiates what form of movement?

a. Antigravity movement

b. Postural adjustment

c. Skilled, voluntary, mostly flexor movement

d. Tremulous, jerky movement

e. None of the above

5. You are presented with a dog with a dense weakness, and proprioceptive placing reaction deficit, of his left front and left back legs. A single pathological site could cause these signs if it were located in the:

a. Left side of the cervical spinal cord

b. Left cerebral cortex

c. Right cerebral cortex

d. Either a or b

e. Either a or c

6. The corticospinal tract simultaneously co-activates both the α and the γ lower motor neurons. If the initial co­activation fails to be sufficient to cause the intended shortening of the muscle, sensory neuron activity of the muscle spindle of that muscle will have what influence on the α motor neurons to the same muscle?

a. AdditionofEPSPs

L. Addition ol IPSPs

c. No influence

d. Decrease in action potential frequency

e. Either b or d