Exam #1: Sensory II

Question 1

What is the Anterolateral System?

Answer 1

This is the ascending sensory tract that relays:

• Nociception
• Temperature

*Note a little light/crude touch

Question 2

What is the definition of nociception?

Answer 2

Physiologyical reception of noxious sensory information elicited by tissue injury

*This can be MEASURED

Question 3

What is pain? How does pain differ from

Answer 3

This is the subjective perception of discomfort in response to stimulation of sensory nerve endings

*This cannot be measured

Question 4

Where is the anterolateral system anatomically?

Answer 4

Ventral/ ventral-lateral

Question 5

What are the two major white matter tracts that are part of the Anterolateral System? Where are these two tracts?

Answer 5

• Anterior Spinothalamic Tract= in the anterior faniculus

- Lateral Spinothalamic Tract= in the anterolateral tract/ ventrolateral tract

Question 6

Aside from the Anterior Spinothalamic Tract & Lateral Spinothalamic Tract, what other tracts are part of the ALS?

Answer 6

• Spinohypothalamic
• Spinomesencephaic
• Spinotectal
• Spinoretiruclar

Question 7

How are the tracts of the ALS classified phylogeneticaly?

Answer 7

1) Neospinothalamic

2) Paleospinothalamic

Question 8

What is the neosplinothalamic system?

Answer 8

• Developed later in evolution i.e. newer
• Direct pathway= information ascends directly from the spine to VLP to somatosensory
• 15 % nociceptive

Question 9

What is the Paleospinothalamic system?

Answer 9

• Older
• Indirect pathway= info goes to the reticular formation–>thalamus
• 85% nociceptive fibers

**Most of the information carried by this pathway is NOT entered into consciousness

Question 10

What is a dermatome?

Answer 10

Band of skin that is innervated by a pair (right & left) of spinal nerves

Question 11

What are the three neurons of the Neospinothalamic Pathway?

Answer 11

1) DRG
2) Dorsal horn
3) VPL of thalamus

Question 12

What type of sensation is carried by the Neospinothalamic Pathway?

Answer 12

• Fast, sharp, & well-localized pain sensation

This information enters CONSCIOUSNESS

Question 13

Where does the central process of the free nerve ending in the Neospinothalamic Pathway enter the spinal cord? What happens here?

Answer 13

Dorsolateral Tract of Lissauer (White Matter)

• Bifurcates into short ascending & descending branches
• Synapse with the Substantis Gelatinosa in the dorsal horn of the gray matter

Question 14

What is the function of the Substantia Gelatinosa?

Answer 14

Modulation of nociception

**Thus, b/c of the SG, some nociception is attenuated

Question 15

After sensory information passes through the SG, where does it go?

Answer 15

• Anterior white commisure
• Axons of the nucleus proprious
• Ascends ventrolateral funiculus

Question 16

Outline the spinothalamic tract.

Answer 16

1) DRG pseudounipolar
2) Interneuron
3) SG
4) Axon from NP
5) Ascend spinal cord–axons to Reticular formation in caudal medulla
6) Pons
7) Midbrain
8) VPL Thalamus
9) Primary somatosensory cortex

Question 17

Where does the decussation of the spinothalamic tract occur?

Answer 17

Spinal cord level

Question 18

What type of fibers convey the nociception from the receptor to the DRG?

Answer 18

A-delta i.e. lightly myelinated

Question 19

What is radicular pain?

Answer 19

Pain resulting from irritation of a dorsal root of a spinal nerve

Question 20

If there is a lesion in the right ascending spinothalamic tract?

Answer 20

Loss of pain & temperature sensation from contralateral side of the body 2+ segments below the lesion b/c of bifurcation of the dorsolateral tract of Lissauer

Question 21

IF the lesion in the neospinothalamic system is in the ascending tract, where are the symptoms?

Answer 21

Opposite or contralateral side

Question 22

Patient has L1 distribution of pain in the left leg. Where could tractotomy be preformed?

Answer 22

T9 on the right

Question 23

Outline the mechanism of referred pain.

Answer 23

• Sensory fibers bringing sensory information from the two involved structures synapses on the SAME second order neuron
• Neospinothalamic tract

Question 24

What is syringomyelia?

Answer 24

This is a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in pain, paralysis, weakness,[1] and stiffness in the back, shoulders, and extremities.

Question 25

What fibers are effected by the enlargement of the central canal of the cord?

Answer 25

Anterior white commissure; carries sensory signals from second order neurons that are crossing over

Question 26

How will occlusion of the Anterior Cerebral Artery effect the ALS?

Answer 26

Sensory deficits in the contralateral leg & foot

Question 27

How will occlusion of the MCA effect the ALS?

Answer 27

Sensory deficits in the contralateral upper limb & foot

Question 28

What are the lenticulostriate arteries?

Answer 28

Branches of the MCA that supply the Thalamus

Question 29

What will occlusion of the lenticulstriate arteries cause in regards to the ALS pathway?

Answer 29

Sesory deficits on the contralateral side

**Note that this is similar to what happens with the DC-ML

Question 30

What does the PCA supply?

Answer 30

Occidental lobe & the inferior temporal lobe, including the spinothalamic tract

Question 31

What does occlusion of the PCA result in, in regards to the ALS?

Answer 31

Sensory deficit on the contralateral side

Question 32

What does the basilar artery supply?

Answer 32

Caudal pons–spinothalamic tract

Question 33

What does occlusion of the basilar artery supply result in, in regards to the ALS?

Answer 33

Contralateral deficits

Question 34

What do the vertebral arteries supply?

Answer 34

Rostral medulla

Question 35

What does occlusion of the vertebral artery supply result in, in regards to the ALS?

Answer 35

Contralateral