10. Somatosensory: Nociception, Thermal Sense & Touch Flashcards
(38 cards)
what is the purpose of the anterolateal system (ALS)
somatosensory system to notify us about tissue damage
-nociception, thermal sensation, nondiscriminative touch, itching to body
what is the basic path for direct ALS pathway
sp cord –> lateral thalamus –> somatosensory cortices
what is the basic path for indirect ALS pathway
sp. cord –> reticular formation –> medial thalamus –> cingulate, frontal & limbic cortices
what fibers make up the ALS
spino—
- —thalamic (direct path)
- —mesencephalic
- —reticular (indirect path)
- —bulbar
- —hypothalamic
what is the basic path of the spinothalamic fibers
spine –> thalamus (VPL & VPI nuclei)
what is the basic path for spinomesencephalic fibers
spine –> reticular formation & periaqueductal gray
what is the basic path of the spinobulbar fibers
spine –> various nuclei of brain
what is the basic path of spinohypthalamic fibers
spine —> hypothalamus & other nuclei
what is the basic path of the spinoreticular fibers
spine –> medulla, pons, midbrain (reticular formation)
=indirect path
what are characteristics of free nerve endings
found all over the body
density varies on body part: more receptors in hands, face
=generic
where do free nerve ending fibers enter the spinal cord
lateral division of post root entry zone
–> stay, ascend, descend 2ish segments at laminae 1, 2, 5
where do free nerve ending fibers fo after they enter the spinal cord
move w/i post.lat. fasciculus (Lissauer Tract)
-ascend/descend after bifurcating
or stay in same level and end on interneuron to stimulate reflex
what are the steps of the direct spinothalamic pathways
nondiscrim tactile, thermal, nociceptive signal –>
enter lat root entry –>
enter post.lat. fasciculus & bifurcate –>
ascending/descending branches end on 2nd order neuron on post horn –>
cross midline via ant commissure –>
move up in contralateral ALS (few ipsi)–>
end on VPL/VPI of thamalus (3rd order)
–> 3rd order neuron to S1
how is the indirect path different than the direct path
terminate on the reticular formation, instead of going up to cortex
-some to VPM and then cortices
=indirect, general feedback from body ==> makes you aware of signal
what are the steps of the indirect spinothalamic pathway
fibers into post horn - ascend/descend & synapse at laminae 2 and 3
–> send axons cross and join the contralat ALS
–> project to reticular formation
–> 3rd order neurons project to intalaminar nuclei & post group nuclei
what is the ALS somatotopic organization
sacral/coccyx - post.lat
most rostral are added in ant.medially (lower cervical & Upper cervical)
what happens when you hace a tumor compresing the cord from lateral to medial at the ALS region
affect lumbar/sacral regions first
what happens if you have an intermedullary tumor damaging the cord from medial to lateral at the ALS region
affect upper cervical first
what is the path for facial sensation
direct/indirect via trigeminal N
primary afferent from trigeminal ganglion –>
attach to sensory/motor roots at ventrolat. pons –>
project down in spinal trigeminal tract to C3 –>
join Lissauer’s (post.lat) tract
–> target VPM
–> 3rd order to part of homunculus that represents face
what is the basic path of the anterior trigminothalamic pathway
face –> spinal cord to 2nd order axon from causal nucleus
–> up as anteriro trigeminothalamic tract
–> contralat VPM
–> posterior limb of internal capsule
–> somatosensory (& limbic cortices)
what is the BS to trigeminal structures in the medulla
PICA
Post. spinal A
what is the anatomical orientation of the face on the spinal trigeminal nucleus
inverterd
V1 inferior & V3 superior
what is the pars caudalis
most caudal part of spinal trigeminal nucleus
from C2/C3 to Obex
-somatotopic head to toe representation –> circumoral/intraoral fibers terminate near obex
–> caudal/lateral fibers terminate in caudal regions of cerival cord
what is pars oralis
spinal trigreminal nucleus part that extends from pons to superior medulla
-tactile info from central face
