Somatosensory Tracts #2 Flashcards
This system is a component of the somatosensory system that includes nociception, crude touch, and temperature.
Anterolateral System (ALS)
***Also known as Spinothalamic Tract
The ALS can be either direct or indirect. What is the general direct pathway?
Spinal cord – Lateral Thalamus – Somatosensory Cortices
The ALS can be either direct or indirect. What is the general indirect pathway?
Spinal cord – Reticular Formation – Medial Thalamus – Cingulate, Frontal, and Limbic Cortices
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.
Spinothalamic (from spine to thalamus)
Spinoreticular (from spine to reticular formation)
Nerve fibers from the free nerve endings travel to the enter the spinal cord through what?
Lateral division of the posterior root
The central target of primary afferents includes the which laminae of the posterior horn?
I, II, and V
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.
Posterolateral fasciculus (Lissauer’s Tract)
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.
True
Nerves transmitting sensory information (primary afferents) from the face come from the cell body of the…
Trigeminal Ganglion
What is the blood supply to the Trigeminal structures in the medulla?
PICA
Posterior Spinal A.
What are the divisions of the Spinal Trigmeinal nucleus?
Pars Caudalis
Pars Oralis
Pars Interpolaris
This division of the Spinal Trigeminal nucleus is the most caudal part extending from the spinal cord (C2, C3) to the Obex.
Pars Caudalis
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.
Pars Oralis
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.
Pars Interpolaris
What provides blood to the ALS?
Sulcal branches of the Anterior Spinal A.
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).
Brown-Sequard
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.
Syringomyelia
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…
Medullary Syndrome
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.
Lateral Medullary (Wallenberg) Syndrome
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.
Spinal Trigeminal
***In response to stimulus that touches the cornea, the eyes blink.
