Lecture 17: Anterolateral system (Spinothalamic tract - STT) Flashcards
Anterolateral system
Functional modalities conveyed
- BLANK
- BLANK
- BLANK: poorly localized tactile sensation (high-threshold mechanoreceptors)
Functional modalities conveyed
- pain (nociceptors)
- thermal sensation (thermoreceptors)
- non-discriminative (crude) touch: poorly localized tactile sensation (high-threshold mechanoreceptors)
The anterolateral system (ALS) is a composite bundle of axons that includes BLANK
Two main functional subdivisions for pain processing:
- direct pathway from BLANK to BLANK)
- well localized pain sensation
- mediates BLANK
- indirect pathway from BLANK to BLANK
- BLANK localized pain sensation
- mediates BLANK
The anterolateral system (ALS) is a composite bundle of axons that includes several tracts
Two main functional subdivisions for pain processing:
- direct pathway from spinal cord to VPL nucleus of thalamus (spinothalamic tract)
- well localized pain sensation
- mediates sensory-discriminative aspects of pain (what, where, when)
- indirect pathway from spinal cord to intralaminar thalamic nucleus (via brainstem reticular formation)
- poorly localized pain sensation
- mediates affective-motivational aspects of pain (emotional and behavioral responses to pain)
INDIRECT IN SPRING
Direct pathway_spinothalamic tract (STT) overview
Neuron 1
Neuron 2
Neuron 3
Key features of primary sensory neurons in direct ALS pathway:
▪ BLANK morphology
▪ BLANK diameter and BLANK myelinated (BLANK) fibers
▪ BLANK pain
▪ receptive fields 2-30 spots (50-180 m diameter each)
Key features of primary sensory neurons in direct ALS pathway:
▪ pseudounipolar morphology
▪ small diameter and lightly myelinated (AGamma) fibers
▪ fast (hot, sharp) pain
▪ receptive fields 2-30 spots (50-180 m diameter each)
Direct pathway_primary sensory neuron
- cell body in BLANK
- central process enters spinal cord in the BLANK of the BLANK and BLANK
- branches enter the BLANK ; superficial to posterior horn)
- descending branches participate in BLANK
- ascending branches synapse in BLANK
- cell body in PRG
- central process enters spinal cord in the lateral division of the posterior root entry zone and bifurcates
- branches enter the posterolateral fasciculus (tract of Lissauer ; superficial to posterior horn)
- descending branches participate in cutaneous spinal reflexes
- ascending branches synapse in posterior horn (may ascend several levels before synapsing)
Direct pathway_primary sensory neuron
- AGamma fibers that enter the spinal cord ascend in the BLANK and synapse mainly in BLANK
- laminae 1 contains projection neurons BLANK
whose axons decussate and travel as ALS fibers to BLANK targets
- AGamma fibers that enter the spinal cord ascend in the posterolateral fasciculus and synapse mainly in lamina 1 of posterior horn
- laminae 1 contains projection neurons (tract cells)
whose axons decussate and travel as ALS fibers to thalamic targets
Direct pathway_neuron 2 (tract cells)
- cell body in BLANK
- lamina 1 receives BLANK fiber input
- axons of BLANK decussate in the BLANK; axons ascend BLANK over 2-3 segments as
they decussate - ascend in the BLANK as BLANK fibers
- cell body in posterior horn
- lamina 1 receives AGamma fiber input
- axons of lamina I neurons decussate in the anterior white commissure; axons ascend rostrally over 2-3 segments as
they decussate - ascend in the contralateral ALS as spinothalamic fibers
Direct pathway_neuron 2 (tract cells)
Direct pathway_neuron 2 (tract cells)
- BLANK fibers
- synapse in BLANK
- BLANK
- spinothalamic fibers
- synapse in VPL
- location, intensity , and quality of pain stimuli
Direct pathway_neuron 3 (VPL neurons)
- STT and PCMLS axons synapse on distinct clusters of BLANK
- axons of VPL neurons ascend to cerebral cortex in the BLANK
- synapse in BLANK for the BLANK
- STT and PCMLS axons synapse on distinct clusters of VPL neurons
- axons of VPL neurons ascend to cerebral cortex in the Posterior limb of the internal capsule
- synapse in S1 for the conscious
appreciation and localization of pain
stimuli
Clinical connection: Dejerine-Roussy (BLANK) syndrome
- lesions inBLANK cause a complete BLANK of BLANK, but over time some patients develop
BLANK; cause not
well understood
Clinical connection: Dejerine-Roussy (Thalamic pain) syndrome
- lesions in** posterior thalamus** cause a complete contralateral
loss of somatosensation, but over time some patients develop
severe, contralateral debilitating pain (dysesthesia); cause not
well understood
ALS receives dual
blood supply in the
spinal cord
ALS (STT)_medulla
ALS (STT)_pons
ALS (STT)_midbrain
ALS (STT)_thalamus and internal capsule
