1. A 25-year-old man was in an automobile accident and suffered a severe spinal cord injury. He had multiple somatic sensory and motor signs. Focusing only on mechanosensation, he had no sense of touch on his right leg and lower trunk, to the level of the umbilicus. Which of the following statements best describes the side and level of injury?

A. Right side of spinal cord at the 10th thoracic segment (T10)
B. Right, T4
C. Left, T10
D. Left, T4

Comment: The touch pathway in the spinal cord is uncrossed; it crosses in the caudal medulla. If the injury were at T4, then the sensory loss would have extended to the upper chest (see Figure 4–5).

2. From which of the listed body regions does the gracile nucleus receive mechanoreceptive input?

A. Contralateral arm
B. Contralateral leg
C. Ipsilateral arm
D. Ipsilateral leg

3. The medial lemniscus—in the medulla, at the level where there is a fourth ventricle—receives its blood supply from which of the following arteries?

A. Posterior inferior cerebellar artery
B. Vertebral artery
C. Posterior spinal artery
D. Anterior spinal artery

Comment: At the most caudal level of the medulla, where there is little or no inferior olivary nucleus, the anterior spinal artery supplies blood to the medial lemniscus.

4. A physician tests vibration sense by touching a tuning fork to the body surface. Which of the following receptors mediates vibration sense?

A. Thermal receptor
B. Pacinian corpuscle
C. Ruffini’s corpuscle
D. Meissner’s corpuscle

5. Which of the following statements best describes the organization of dermatomes associated with adjacent dorsal roots?

A. Dermatomes are adjacent, with minimal overlap, so that loss of one dorsal root gives rise to a loss of somatic sensation within the dermatome boundary, as shown in the dermatome maps.
B. Dermatomes overlap partially, but loss of one dorsal root does not give rise to a noticeable loss of sensation.
C. Dermatomes overlap partially, so that loss of one dorsal root typically gives rise to a noticeable loss of sensation within the dermatomal boundaries.
D. Dermatomes overlap nearly completely, so that loss of one dorsal root typically does not give rise to a noticeable loss of sensation.

6. You are testing sensory function in a patient. She has an upper extremity limb position sense impairment. Which of the following best describes the sensory receptor that is most important for limb proprioception?

A. Merkel’s receptor
B. Muscle spindle receptor
C. Bare nerve ending
D. Golgi tendon organ

Comment: Note that primary muscle spindle receptors synapse on motor neurons in the ventral horn. Whereas the muscle spindle receptor synapses on motor neurons in the ventral horn, the receptor’s ascending branch in the dorsal column is responsible for proprioception.

7. A patient has a small thalamic stroke that affects mechanosensation on the foot. Which nucleus is most likely affected?

A. Medial division of the ipsilateral ventral posterior nucleus
B. Medial division of the contralateral ventral posterior nucleus
C. Lateral division of the ipsilateral ventral posterior nucleus
D. Lateral division of the contralateral ventral posterior nucleus

8. Occlusion of which artery would most likely damage the ventral posterior nucleus?

A. Branches of the middle cerebral artery
B. Branches of the anterior cerebral artery
C. Branches of the posterior cerebral artery
D. Branches of the basilar cerebral artery

9. Complete the following analogy: The face area of the primary somatic sensory cortex is to the leg area, as

A. the middle cerebral artery is to the posterior cerebral artery
B. the middle cerebral artery is to the anterior cerebral artery
C. the posterior cerebral artery is to the anterior cerebral artery
D. the posterior cerebral artery is to the middle cerebral artery

10. After a traumatic head injury, a 45-year-old woman develops a seizure disorder. Initially, she experiences a tingling sensation in her right leg. This is followed by tingling on her right back, then right palm, fingers, and finally the right side of the face. Which of the following best describes the locations in the brain of the start and end of the seizure?

A. Start: medial left postcentral gyrus; end: lateral left postcentral gyrus
B. Start: medial left postcentral gyrus; end: left insular cortex
C. Start: left ventral posterior medial nucleus; end: left ventral posterior lateral nucleus
D. Start: left ventral posterior lateral nucleus; end: left ventral posterior medial nucleus

Comment: Response D has the correct somatotopy to explain the seizure progression, like the correct response (A). However, this seizure progression is classically within the postcentral gyrus. It progresses because of local connections within the cortex. Connectivity within the thalamus does not support this kind progression.