Chapter 6: Somatosensory System

Chapter 6: Somatosensory System

Complete Chapter Questions With Answers

Sample Questions Are Posted Below

1. Spinal axons conveying a signal for conscious somatosensation from the upper limb ascend in which of the following?
2. Ventral horn
3. Fasciculus gracilis
4. Fasciculus cuneatus
5. Internal arcuate fibers
6. Medial lemniscus

ANS: C

Rationale: Conscious somatosensory information from peripheral receptors is conveyed to the dorsal root and ascends through the ipsilateral dorsal column. Axons from the lower limb ascend in the medial dorsal column, called the fasciculus gracilis. Axons from the upper extremity ascend in the lateral dorsal column, called the fasciculus cuneatus.

2. Cell bodies of second-order neurons conveying a signal for conscious proprioceptive information from the lower limb are located in which of the following?
3. Dorsal root ganglion
4. Fasciculus cuneatus
5. Somatosensory cerebral cortex
6. Nucleus gracilis
7. Medial lemniscus

ANS: D

Rationale: First-order neurons conveying conscious proprioceptive input enter the dorsal root, with cell bodies located in the dorsal root ganglion. First-order neurons from the lower limb synapse with second-order neurons whose cell bodies are located in the nucleus gracilis of the medulla.

3. The ventral posterolateral (VPL) nucleus of the thalamus is the site of synapse for:
4. First-order neurons of the dorsal column/medial lemniscus system.
5. Second-order neurons with their cell bodies in the nucleus cuneatus and/or nucleus gracilis.
6. Third-order neurons with their cell bodies in the spinal nucleus of the trigeminal cranial nerve.
7. Second-order neurons with their cell bodies in the nucleus dorsalis (Clarke’s nucleus).
8. Third-order neuron with their cell body the lateral cuneate nucleus.

ANS: B

Rationale: Second-order neurons, with their cell bodies located in the nucleus gracilis or nucleus cuneatus, cross the midline as the internal arcuate fibers and ascend to the thalamus as the medial lemniscus. These fibers then synapse with third-order neurons in the VPL nucleus of the thalamus.

4. Rapidly turning the eyes and head toward a painful stimulus is a function of which one of the following tracts?
5. Trigeminoreticulolimbic
6. Spinoreticular
7. Spinomesencephalic
8. Trigeminospinothalamic
9. Dorsal column medial lemniscus

ANS: C

Rationale: The spinomesencephalic tract carries nociceptive information to the superior colliculus and periaqueductal gray matter, producing a rapid turning of the eyes and head toward the source of the noxious input.