Somatosensory Tracts #2

Question 1

This system is a component of the somatosensory system that includes nociception, crude touch, and temperature.

Answer 1

Anterolateral System (ALS)

***Also known as Spinothalamic Tract

Question 2

The ALS can be either direct or indirect. What is the general direct pathway?

Answer 2

Spinal cord – Lateral Thalamus – Somatosensory Cortices

Question 3

The ALS can be either direct or indirect. What is the general indirect pathway?

Answer 3

Spinal cord – Reticular Formation – Medial Thalamus – Cingulate, Frontal, and Limbic Cortices

Question 4

Fibers of the ALS will split off to travel to different sarges in the brain. The __________ tract is also considered the direct pathway, and the _________ tract is considered the indirect pathway.

Answer 4

Spinothalamic (from spine to thalamus)

Spinoreticular (from spine to reticular formation)

Question 5

Nerve fibers from the free nerve endings travel to the enter the spinal cord through what?

Answer 5

Lateral division of the posterior root

Question 6

The central target of primary afferents includes the which laminae of the posterior horn?

Answer 6

I, II, and V

Question 7

In the ALS, once the fibers are in the spinal cord, they move within the _________ _________. Most ascend or descend 2 spinal levels after bifurcating, and also cross the spinal cord.

Answer 7

Posterolateral fasciculus (Lissauer’s Tract)

Question 8

T/F. For the indirect pathway of the ALS, instead of projecting all the way to the somatosensory cortex, it terminates in the reticular formation to provide indirect and general feedback from the body. There is more of an awareness of pain (i.e., dull aching) rather than a specific sharp sensation of pain.

Answer 8

True

Question 9

Nerves transmitting sensory information (primary afferents) from the face come from the cell body of the…

Answer 9

Trigeminal Ganglion

Question 10

What is the blood supply to the Trigeminal structures in the medulla?

Answer 10

PICA

Posterior Spinal A.

Question 11

What are the divisions of the Spinal Trigmeinal nucleus?

Answer 11

Pars Caudalis
Pars Oralis
Pars Interpolaris

Question 12

This division of the Spinal Trigeminal nucleus is the most caudal part extending from the spinal cord (C2, C3) to the Obex.

Answer 12

Pars Caudalis

Question 13

This division of the Spinal Trigeminal nucleus extends from the level of entry (pons) to the superior medulla. It receives tactile info from central face.

Answer 13

Pars Oralis

Question 14

This division of the Spinal Trigeminal nucleus extends from the superior medulla to the Obex. It receives info from the peripheral face. It projects to the cerebellum via the inferior cerebellar peduncle and relays tactile info to the contralateral VPM.

Answer 14

Pars Interpolaris

Question 15

What provides blood to the ALS?

Answer 15

Sulcal branches of the Anterior Spinal A.

Question 16

This can occur from hemisection of the Spinal Cord. It presents of loss of contralateral nociceptive and thermal sensations of the body and ipsilateral loss of discriminative touch, vibration, and proprioception. There can also be motor loss with paralysis of extremities (depending on level).

Answer 16

Brown-Sequard

Question 17

This is occurs when there is cystic cavitation of central regions of spinal gray matter. It may impinge on anterior white commissure that contains decussating ALS fibers. This results in bilateral loss of nociceptive and thermal sensations, and crude touch. There is a “cape-like” distribution of loss over the shoulders and down to the nipple level.

Answer 17

Syringomyelia

Question 18

When there is a lesion at the medial portion of the Medulla, there is contralateral loss of discriminative touch and vibratory sense. This is known as…

Answer 18

Medullary Syndrome

Question 19

This occurs due to a lesion to the Posterior Inferior Cerebellar A. (PICA). This artery supplies the territory of the ALS and the Spinal Trigeminal Nucleus/Tract. It results in a loss of contralateral pain and temperature sensation over the body and ipsilateral loss of pain and temperature over the face.

Answer 19

Lateral Medullary (Wallenberg) Syndrome

Question 20

For the corneal reflex, afferent limbs originate from pain/touch receptors in the cornea. Fibers travel on V1 and have cell bodies in the Trigeminal Gangion which terminate in the ipsilateral ________ _______ Nucleus. Trigeminothalamic fibers then send collaterals bilaterally into the facial motor nucleus (efferent limb) of this reflex.

Answer 20

Spinal Trigeminal

***In response to stimulus that touches the cornea, the eyes blink.