Flashcards in Tracts Deck (70)
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1
Each dorsal rootlet is divided into two divisions
lateral and medial division
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lateral divison
A delta/C fibers, GSA's, enter area of white mater @ tip of dorsal horn via lissauer's tract, they then ascend or descent 1 or 2 cord segments, then enter grey mater and synapse
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medial division
A beta/type I, II, and III; DO NOT USE LISSAUER'S TRACT, synapse in lamina III and IV, or in lower motor neuron (muscle stretch reflex: I A fiber, quick change in length of extrafusal fibers, synapse of alpha motor neuron (monosynaptic reflex)).
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tract
organized bundle of axons (white mater)
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ascending tracts
modulated by descending tracts by location of cell bodies**
- arousal, affective, motivation responses of stimulus
- unconscious monitoring/control of motor activity (posture/movement)
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first order neurons
sensory neuron (A delta, A beta, type I)
- cell bodies are always in dorsal root ganglion
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second order neurons
synapse in thalamus, neuron cell bodies in the thalamus
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third order neurons
thalamocortical neurons
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dorsal column/medial lemniscus (location)
dorsal column - ipsilateral fibers in dorsal white mater-cord
medial lemniscus - contralateral fibers in brain stem
cross @ tegmentum of caudal medulla
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dorsal column/medial lemniscus (information conveyed)
vibration, joint position, 2pt touch (and light touch), pressure (association cortex)
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association cortex
the ability to feel and recognize an object in one's hand while not looking
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dorsal column/medial lemniscus (1st order neurons)
1st order - in DRG
- axons S5-T6 ascend via fasciculus gracilis
- axons T5 - C1 ascend in the fasciculus cuneatus
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dorsal column/medial lemniscus (2nd order neurons)
cell bodies are in the nuclei gracile and cuneatus
- axons cross as the internal arcuate fibers and ascend as the medial lemniscus
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dorsal column/medial lemniscus (3rd order neurons)
cell bodies are in the VPL thalamic nucleus
- axons course through the internal capsule to the sensory cortex, postcentral gyrus/post paracentral lobule (homunculus)
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dorsal column/medial lemniscus 1st 2nd and 3rd order neurons are ________ organized
somatotopically
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anterolateral system conveys
pain and temperature (some touch and pressure)
- A delta/C fibers
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anterolateral system - A delta fibers
fast conducting; localized sharp/acute pain
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anterolateral system - C fiber
slow conducting; poorly localized; burning; aching pain
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anterolateral system cross at
ventral white commissure
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anterolateral system includes three tracts...
spinothalamic, spinoreticular, spinomesencephalic
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ALS - spinothalamic system includes...
neospinothalamic (somatotopically organized) and paleospinothalamic
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ALS - spinothalamic - neospinothalmic
1st order - A delta
2nd order - lamina I and V (VI-VII) and axons cross and ascend
3rd order - VPL of thalamus
conveys: sharp, well localized, discriminatory pain
terminates @ primary sensory cortex (homunculus)
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ALS - spinothalamic - paleospinothalamic
1st order - C fibers
2nd order - lamina VII - VIII and axons cross and ascend
- collaterals go to reticular formation
3rd order - intralaminar thalamic nucleus
conveys: dull achy pain
terminates @ widespread cortex
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ALS - spinoreticular tract conveys
- dull achy
- autonomic, behavioral, and emotional responses to the painful stimuli
- arouses cortex to maintain alertness and attentiveness (focus attention on a painful area)
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ALS - spinoreticular tract neurons
1st - afferent from cutaneous receptors
2nd - contralateral to pontine and medullary reticular formation and ipsilateral to medullary reticular formation
3rd - thalamic nuclei, then cortex via anterior cingulate/insular cortices
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ALS - spinomesencephalic tract conveys
reflex responses
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ALS - spinomesencephalic tract neurons
1st - synapse in grey mater
2nd - cross in ventral white commissure, then synapse @ super colliculus for reflex response or synapse @ periaqueductal grey
- PAG: descending feedback to dorsal horn; synapse in reticular formation to modulate pain
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ALS - spinothalamic - neospinothalamic
vs.
ALS - spinothalamic - reticular/mesencephalic/hypothalamic
neospinothalamic: seriousness of the pain (posterior partietal lobe, insula of amgdala, anterior cingulate cortex: prefrontal cortex)
reticular/mesencephalic/hypothalamic: pain is uncomfortable (brainstem nuclei, thalamus, hypothalamus)
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anterior cingulate cortex (ACC)
function: emotional component of pain
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