Somatosensory Tracts: Nociception, Thermal Sense, and Touch Flashcards
The Anterolateral System is responsible for the perception of nociception (pain), temperature, and non-discriminatory touch (crude touch). VEry generally it’s divided into direct and indirect pathways that travel different routes and convey different types of pain. What are the general routes taken by the direct and indirect pathway?
Direct Pathway
Spinal cord > Lateral THalamus > Somatosensory Cortex
Indirect Pathway
Spinal Cord > Reticularformation > Medial Thalamus > Cingulate, Frontal, and Limbic Cortcies
The Anterolateral System is comprised of fiber bundles that split off to travel to different targets. These fibers are either direct or indirect. Listed below are these fibers, for the bolded fibers indicate whether they are dirrect or indirect.
Spinothalamic
Spinomesencephalic
Spinoreticular
Spinobulbar
Spinohypothalamic
Spinothalamic: Direct
Spinomesencephalic: Indirect
Spinoreticular: Indirect
Where do the direct fibers of the Spinothalmic tract go?
Spine > Thalmus > Ventral Posterlateral Nuclei& VEntral Posterior Inferior Nuclei
Where do the indirect fibers of the Spinomesencephalic fibers go?
Spine > Midbrain Reticular Formation & Periaqueductal Gray
Which of the following ALS fibers fo to the medulla, pons and midbrain?
A. Spinohypothalmic
B. Spinobulbar
C. Spinoreticular
D. Spinothalamic
Spinoreticular
T/F: Free nerve endings don’t have specialized receptor cells, so sensation is transmitted through ligand-gated ion channels, glutamate receptors, and G-protein coupled receptors
True
In the central pathway of the ALS, free nerve fibers enter the spinal cord through what location?
Lateral Division of the Posterior Root
The Central Target of the primary afferents specifically decussate in what 3 laminae?
1, 2, 5
In the central pathway, once the fibers reach the spinal cord, they move within what structure and can cross ascend and descend?
Lissauers Tract (Posterolateral Fasciculus)
In the central pathway, most fibers cross across the spinal cord and ascend/descend after bifurcating. Other fibers can also stay at the same spinal level and terminate on interneurons. What action do these fibers relate to?
Reflexes
What type of sensory does the Direct Spinothalmic Pathway provide?
Non-discriminitive touch
Thermal (harmful temperatures)
Nociceptive Signals
Where do the descending branches of the Direct Spinothalmic Pathway terminate?
What actions do they contribute to?
Interneurons in the gray matter
Spinal reflexes
Ascending 2nd order neurons in the direct spinothalamic pathway cross the midline via the anterior white commissure and synapse on the 3rd order neurons in what location?
Venteral Posterolateral region of the thalamus
Instead of projecting to the somatosensory cortex, the indirect pathway targets what structure?
What type of sensation does it provide?
REticular Formation
Awareness of pain
Essentially the indirect spinothalamic pathways provide signals that your body is aware of but not as directly
Fibers of the indirect spinothalmic pathway ascend and descend in what fasciculus?
The fibers synapse in what laminae?
Posterolateral Fasciculus
Laminae 2, 3, and 5-8
Fibers of the indirect spinothalmic pathway ascend _______ which is is hwy its hard to specify the pain
Fibers of the indirect spinothalmic pathway ascend bilaterallywhich is is hwy its hard to specify the pain
The ALS is somatotopic. Axons from the lower levels (coccygeal, sacral of the body are found more ________, while more rostral levels are added in an _________ sequence.
The ALS is somatotopic. Axons from the lower levels (coccygeal, sacral of the body are found more posterolateral, while more rostral levels are added in an anteromedial sequence.
An extramedullary tumor is found compressing the spinal cordfrom the lateral to medial direction. Which of the following areas would you most likely begin to see issues?
A. Cervical
B. Thoracic
C. Lumbar
D. Sacral and Coccygeal
Sacral and Coccygeal
Nerves transmitting sensory information (primary afferents) come from the cell body of what ganglion?
Trigeminal Ganglion
Sensation goes to the face carried by CN V, and once it gets to the trigeminal ganlgion it will _________ into the brainstem and merfe with the ______ trigeminal tract in C3, lateral to teh nucleus. The information then projects down to join the ___________.
Sensation goes to the face carried by CN V, and once it gets to the trigeminal ganlgion it will DESCEND into the brainstem and merfe with the SPINAL trigeminal tract in C3, lateral to teh nucleus. The information then projects down to join the LISSAUER’S TRACT.
Second order axons from the caudal nucleus decussate and ascend in what tract for facial sensory distribution?
Where does the second-order axon terminate?
Anterior Trigeminothalmic Tract
Contralateral VPM of Thalamus
T/F: The anatomic orientation of the trigeminal nerve branches is inverted in the spinal trigeminal tract and nucleus
True
Blood supply to trigeminal structures in the medulla come from what two arteries?
Posterior Inferior Cerebellar A
Posterior Spinal A.
Which of the following extends from the level of entry (pons) to the superior medulla. It also recieves tactile info from central face.
A. Pars Caudalis
B. Pars Oralis
C. Pars Interpolaris
D. None of the above
Pars Oralis
Which of the following extends from the superior medulla to obex, and receieves tactile information from the peripheral face?
A. Pars Caudalis
B. Pars Oralis
C. Pars Interpolaris
D. None of the above
Pars Interpolaris
Hemisection of the spinal cord results in Brown-Sequard Syndrome. What are the general affects of this syndrome
ALS damage: Controlateral loss of nociception and thermal sensation over body (can start two segments below)
Medial Lemniscal Damage: Ipsilateral loss of Tactile, vibratory, and proprioception (can cause flaccid paralysis)
Motor Deficits: Ipsilateral paralysis of extremities (can lead to spastic paralysis)
Syringomyelia is cystic cavitation of the central regions of the grey matter may impinge on the Anterior White Commissure that contains the decussating ALS fibers. What happens when syringomyelia happens at C4-C5?
Bilateral loss of nondiscriminitive tactile, nocieptive, and thermal censations
What is postherpetic neuralgia?
“worst pain of your life” experienced as a result of Herpes Zoster Infection
In the medulla, ALS fibers are near the anterolateral surface, so a lesion at the medial portion of the medulla can cause what presentation of Medullary Syndrome?
Contrlateral loss of discriminitive touch and vibratory sense, but pain and thermal sensation remain intact
“dissociative sensory loss”
Lateral Medullary Syndrome aka Wallenberg syndrome is a vascular lesion to what artery that supplies the anterolateral system and the spinal trigeminal nucleus/tract?
What deficits will you see in the Wallenberg Syndrome?
Posterior Inferior Cerebellar A.
Contralateral loss of pain and temperature over body
Ipsilateral loss of pain and temperature over the face
Nice
