NEUROSCIENCE: PRACTICE EXAMINATION QUESTIONS

SENSORY FUNCTION and SOMATIC SENSATION

Choose the one best answer or completion.

1. The generator (receptor) potential in sensory endings is due to

1. increased rate of active transport by the Na-K-ATPase pump
2. release of stored Ca²⁺ from intracellular stores
3. opening of voltage-gated ion channels
4. opening of non-selective ion channels
5. closing of K⁺ selective ion channels

2. "Lateral inhibition" is a mechanism for

1. preventing excess stimulation of sensory endings
2. increasing the precision of stimulus localization
3. selectively reducing the intensity of pain sensation
4. increasing sensitivity to low intensity stimuli
5. responding to complex stimuli, such as "wetness"

3. Pacinian corpuscles are characterized by all of the following except

1. rapid adaptation
2. axons travel in the dorsal column system
3. innervated by small myelinated axons (Ad)
4. sense rapid vibration
5. project to the somatosensory cortex

4. When skin temperature is rapidly raised from 25 C to 35 C, the expected sequence of sensation during and after the temperature change is

1. sensation of gradual warming after the skin temperature has reached 35 C
2. initial sensation of intense warmth followed by a sensation of mild warmth
3. initial sensation of warmth followed by a rebound sensation of cold
4. no particular sensation, since cutaneous thermoreceptors are sensitive only to temperature below 25 C or above 35 C
5. no particular sensation, since at 35 C warm and cold receptors fire at the same rate

4. The spinoreticular tract is important for which of the following?

1. sensation localization
2. determining the modality of the sensation
3. cerebral cortex arousal
4. increasing sensation acuity (discrimination of detail)
5. none of the above, since the reticular formation is important in motor activity, not sensation

5. If a patient shows sensory loss at one dermatome and all ipsilateral dermatomes below it, then it is likely that the lesion is located in:

1. a peripheral nerve
2. a spinal nerve
3. a spinal root
4. the spinal cord
5. the brainstem

6. Loss of touch-pressure sensation from dermatomes T5-T6-T7 on the right side with normal sensation otherwise could be due to

1. destruction of the right dorsal root ganglia at T5-T6-T7
2. a tumor pressing on the medial aspect of nerves entering the spinal dorsal horn at T5-T6-T7 on the right side
3. a lesion of the right dorsal column just above T5
4. a lesion of the left dorsal column just above T5
5. a lesion in the ventral white commissure at T5-T6-T7

7. When you sit down gently on a chair, all of the following are involved in signaling that your posterior has contacted the seat except

1. ascending dorsal column axons
2. cuneate fasciculus
3. VPL nucleus
4. medial lemniscus
5. thalamo-cortical projection fibers

8. All of the following pairs match fiber tracts with cells of origin, except:

1. trigeminal lemniscus - main sensory nucleus of the trigeminal
2. fasciculus cuneatus - dorsal root ganglion
3. spinothalamic tract - dorsal root ganglion
4. pyramidal tract - cerebral cortex
5. none of the above that is, none are exceptions as all are valid matches

9. Loss of pain and temperature sensation from the left side of the face with other facial sensation remaining normal could be due to a lesion in the

1. left trigeminal lemniscus
2. right trigeminal lemniscus
3. left trigeminal caudalis subnucleus
4. right trigeminal caudalis subnucleus
5. left trigeminal mesencephalic nucleus

10. During a neurological examination, a patient cannot tell with his eyes closed whether the neurologist flexed or extended his toe, there is likely damage to

1. the fasciculus cuneatus
2. the fasciculus gracilis
3. the anterolateral system
4. lamina II of the dorsal horn
5. the ventral white commissure

11. Which of the following synapse in the trigeminal mesencephalic nucleus?

1. afferents from oral mechanoreceptors
2. afferents from oral pain and temperature receptors
3. afferents from facial muscle proprioceptors
4. efferents to the jaw opening and closing muscles
5. none of the above

12. Brodmann’s areas 1-2-3a-3b of the primary somatosensory cortex differ in the

1. area of the body they represent, with area 1 mapping the most caudal regions and 3b the most rostral
2. stimulus intensity to which they response, with area 1 response to gentle stimuli and 3b to the most intense stimuli
3. side of the body they represent, with 1 and 3a responding to contralateral stimuli and 2 and 3b responding to ipsilateral stimuli
4. modality/submodality to which they respond
5. sequence in the neuronal chain, with area 1 responding to 1st order neurons, area 2 to 2nd order neurons, etc.

The following question is of the short answer type. Answer each section in a few sentances.

13. Define/describe each of the following:

1. Sensory cortex "column"
2. Primary sensory cortex somatotopic map
3. Dermatome