Chapter 7 : Tracts of the Spinal Cord (2)

Question 1

1. The ability to recognize an unseen familiar object placed in the hand depends on the integrity of which pathway? (A) Spinospinal tract (B) Dorsal column (C) Dorsal spinocerebellar tract (D) Spino-olivary tract (E) Spinothalamic tract

Answer 1

l-B. The ability to recognize the form and texture of an unseen familiar object is called stereognosis. This is an important function of the dorsal column-medial lemniscus system.

Question 2

2. All of the following statements concerningthe corticospinal tracts are correct EXCEPT (A) they arise from lamina V of the cerebralcortex (B) they arise from upper motor neurons(UMNs) (C) they descend through the anterior limbof the internal capsule (D) they undergo a 90% decussation in thecaudal medulla (E) they descend through the base of thepons

Answer 2

2-C. The corticospinal tracts arise from UMNs found in lamina V of the cerebral cortex. They descend through the posterior limb of the internal capsule, the middle third of the crus cerebri(basis pedunculi) of the midbrain, and the base of the pons and constitute the medullary pyramids. Ninety percent of the corticospinal fibers decus sate in the caudal medulla as the pyramidal decussation.

Question 3

3. All of the following statements concerningthe dorsal spinocerebellar tract are correct EXCEPT (A) it is an uncrossed tract (B) it enters the cerebellum via the superiorcerebellar peduncle (C) it subserves unconscious proprioception (D) it terminates in the cerebellar vermis (E) it receives input from muscle spindlesand Golgi tendon organs

Answer 3

3-B. The uncrossed dorsal spinocerebellar tract enters the cerebellum via the inferior cerebellar peduncle and terminates in the cerebellar vermis. It receives input from muscle spindles and Golgi tendon organs and subserves unconscious proprio ception.

Question 4

4. Which statement concerning the rubrospinaltract is FALSE? (A) It lies ventral to the lateral corticospinaltract in the spinal cord (B) It arises from the red nucleus of the midbrain (C) It is an upper motor neuron (UMN) tract (D) It is a crossed tract (E) It plays a role in the control of extensortone

Answer 4

4-E. The rubrospinal tract, an upper motor neuron (UMN) tract, originates in the red nucleus of the midbrain, crosses in the ventral tegmental decus sation of the midbrain, traverses the tegmentum of the pons and medulla, and terminates in the ventral horn of the spinal cord. In the spinal cord, the tract lies in the lateral funiculus ventral to the lateral corticospinal tract. It plays a role in regulating flexor tone.

Question 5

5. Destruction of the ventral horn results inall of the following deficits EXCEPT (A) loss of muscle stretch reflexes (MSRs) (B) loss of muscle bulk (C) flaccid paralysis (D) Babinski’s sign (E) loss of superficial abdominal reflexes

Answer 5

5-D. Destruction of ventral horn motor neurons results in a lower motor neuron (LMN) lesion and is characterized by flaccid paralysis, muscle atrophy (loss of muscle bulk), and areflexia (loss of muscle stretch and superficial abdominal reflexes). Babinski’s sign is not seen in LMN disease.

Question 6

6. All of the following tracts decussate in theventral white commissure EXCEPT the (A) lateral spinothalamic tract (B) ventral spinocerebellar tract (C) ventral corticospinal tract (D) dorsal spinocerebellar tract (E) ventral spinothalamic tract

Answer 6

6-D. The dorsal spinocerebellar tract is an uncrossed tract.

Question 7

7. The corticospinal tracts receive contributionsfrom all of the following areas EXCEPT (A) prefrontal cortex (B) premotor cortex (C) motor cortex (D) somatesthetic cortex (E) paracentral lobule

Answer 7

7-A. The corticospinal (pyramidal) tracts receive contributions from the premotor (area 6), motor (area 4), and the sensory or somatesthetic (areas 3, 1, and 2) cortices. They receive approximately one-third of their axons from each of these cortical areas. The paracentral lobule represents a continu ation of the motor and somatesthetic cortices onto the medial aspect of the hemisphere. The prefrontal cortex lies rostral to the premotor cortex.

Question 8

8. All of the following statements concerningthe lateral spinothalamic tract are correctEXCEPT (A) it projects collaterals to the reticular formation (B) it projects to intralaminar nuclei of thethalamus (C) it projects to the ventral posteromedial(VPM) nucleus of the thalamus (D) it mediates pain and temperature (E) its cells of origin are in the dorsal horn

Answer 8

8-C. The lateral spinothalamic tract mediates pain and temperature sensation and projects to the reticular formation of the brainstem and to the ventral posterolateral (VPL) and intralaminar nuclei of the thalamus. First-order neurons are in the dorsal root ganglion, second-order neurons (cells of origin) are in the dorsal horn, and third order neurons lie in the VPL nucleus of the thalamus.

Question 9

9. All of the following statements concerningthe dorsal column-medial lemniscus pathwayare correct EXCEPT (A) it has second-order neurons in themedulla (B) it receives input from Pacini’s and Meissner’scorpuscles (C) it decussates in the spinal cord (D) it mediates kinesthetic sensation (E) it mediates vibration sensation

Answer 9

9-C. The uncrossed dorsal columns consist of the fasciculus gracilis and the fasciculus cuneatus and mediate tactile discrimination, form recognition , vibration, movement, and joint and muscle sensation (proprioception). They receive input from tactile receptors (Pacini’s and Meissner’s corpuscles), muscle spindles, joint receptors, and Golgi tendon organs. The dorsal column-medial lemniscus pathway decussates in the caudal medulla (decussation of the medial lemniscus). First-order neurons are in the dorsal root ganglion; second-order neurons are in the gracile and cuneate nuclei of the medulla; and third-order neurons are in the VPL nucleus of the thalamus.

Question 10

Match each statement below with the appropriatespinal cord tract. (A) Cuneocerebellar tract (B) Cuneate fasciculus (C) Dorsal spinocerebellar tract (D) Lateral corticospinal tract (E) Lateral spinothalamic tract (F) Lissauer’s tract (G) Vestibulospinal tract 10. Contains axons from the giant cells of Deiters

Answer 10

10-G. The vestibulospinal tract arises from the giant cells of Deiters found in the ipsilateral lateral vestibular nucleus of the pons. The vestibulo spinal tract facilitates extensor muscle tone.

Question 11

Match each statement below with the appropriatespinal cord tract. (A) Cuneocerebellar tract (B) Cuneate fasciculus (C) Dorsal spinocerebellar tract (D) Lateral corticospinal tract (E) Lateral spinothalamic tract (F) Lissauer’s tract (G) Vestibulospinal tract 11. Is the upper extremity equivalent of atract that arises from the cells of Clarke’scolumn

Answer 11

11-A. The cuneocerebellar tract is the upper extremity equivalent of the dorsal spinocerebellar tract, which arises from the cells of Clarke’s column. The cuneocerebellar tract arises from cells of the accessory cuneate nucleus, a homolog of the nucleus of Clarke.

Question 12

Match each statement below with the appropriatespinal cord tract. (A) Cuneocerebellar tract (B) Cuneate fasciculus (C) Dorsal spinocerebellar tract (D) Lateral corticospinal tract (E) Lateral spinothalamic tract (F) Lissauer’s tract (G) Vestibulospinal tract 12. Conveys nociceptive input from the contralateralside of the body

Answer 12

12-E. The lateral spinothalamic tract conveys nociceptive input from the contralateral side of the body.

Question 13

Match each statement below with the appropriatespinal cord tract. (A) Cuneocerebellar tract (B) Cuneate fasciculus (C) Dorsal spinocerebellar tract (D) Lateral corticospinal tract (E) Lateral spinothalamic tract (F) Lissauer’s tract (G) Vestibulospinal tract 13. Contains axons from the giant cells ofBetz

Answer 13

13-D. The lateral corticospinal tract contains axons from the giant cells of Betz. The giant pyramidal cells of Betz are found in the precentral gyrus and in the anterior paracentral lobule.

Question 14

Match each statement below with the appropriatespinal cord tract. (A) Cuneocerebellar tract (B) Cuneate fasciculus (C) Dorsal spinocerebellar tract (D) Lateral corticospinal tract (E) Lateral spinothalamic tract (F) Lissauer’s tract (G) Vestibulospinal tract 14. Contains ipsilateral pain fibers that havetheir second-order neurons in the dorsal horn

Answer 14

14-F. The dorsolateral tract of Lissauer contains ipsilateral pain fibers that have their secondorder neurons in the dorsal horn.

Question 15

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.

15. Projects to the cerebellum via the inferiorcerebellar peduncle

Answer 15

15-B. The dorsal spinocerebellar tract projects unconscious proprioceptive information (muscle spindles and Golgi tendon organs) to the cerebellum via the inferior cerebellar peduncle.

Question 16

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.

16. Mediates pain and temperature sensation

Answer 16

16-C. The lateral spinothalamic tract lies between the ventral spinocerebellar tract and the ventral horn. It mediates pain and temperature sensation.

Question 17

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.
17. Cells of origin are found in the precentralgyrus

Answer 17

17-E. The lateral corticospinal tract has its cells of origin in the premotor, motor, and sensorycortices. The precentral gyrus and the anterior paracentral lobule are motor cortices and contain the motor homunculus. It gives rise to one-third of the fibers of the corticospinal (pyramidal) tract.

Question 18

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.

18. Mediates two-point tactile discriminationfrom the hand

Answer 18

18-F. The fasciculus cuneatus mediates two-point tactile discrimination from the hand.

Question 19

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.
19. Myelination not fully achieved until theend of the second year

Answer 19

19-E. The corticospinal (pyramidal) tracts are not fully myelinated until the end of the second year. For this reason, Babinski’s sign may be elicited in young children.

Question 20

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.

20. Transection results in spasticity

Answer 20

20-E. Transection of the lateral corticospinal tract results in spastic paresis (exaggerated muscle stretch reflexes and clonus).

Question 21

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.

21. Plays a role in regulating extensor tone

Answer 21

21-D. The vestibulospinal (lateral) tract, found ventral to the ventral horn, plays a role in regulating extensor tone.

Question 22

Match each description of a spinal cord tractwith the appropriate lettered structure shownin the illustration.
22. Transmits vibration sensation from theAnkle

Answer 22

22-A. The fasciculus gracilis transmits vibratory sensation (pallesthesia) from the lower extremities.