Tracts

Question 1

neospinothalamic tract

Answer 1

1st order nociceptive neurons in DRG synapse w/ Rexed layer I neurons in marginal zone –> layer I neurons decussate in ant white comissure –> lat spinothalamic tract –> VPL & VPI nuclei in thal –> primary somatosensory cortex

Question 2

sensory and spinal trigeminal tracts

Answer 2

1st order nociceptive neurons from head, face, intraoral structures in trigeminal ganglion synapse w/ spinal trigeminal nucleus –> decussate to trigemimnothalamic tract/trigeminal lemniscus –> Adelta fibers go to VPM thal, C fibers go to parafasiculus & centromedian thal (aka PF-CM complex in intralaminar thal) –> both synapse to primary somatosensory cortex

Question 3

paleospinothalamic tract (consists of the 3 tracts). what’s their innervation and why? what can this pathway activate?

Answer 3

1st order nociceptive neurons synapse in Rexed layer 2; 2nd order neurons synapse in Rexed layers 4-8 –> decussate to ant spinal thalamic tract. in mesencephalic retic formation & periaqueduct gray => spinoreticular tract; in tectum => spinotectal/medullary tract; in PF-CM complex => spinothalamic tract. bil b/c some ascending fibers don’t cross to opposite cord. brain stem nuclei for descending pain suppression pathway

Question 4

archispinothalamic tract. what rxns to pain does this tract produce?

Answer 4

1st order nociceptive neurons synapse w/ Rexed layer 2, 4-6 –> thru multisynaptic propriospinal pathways surrounding grey matter to synapse w/ MRF-PAG, PF-CM complex, hypothal & limbic system nuclei. visceral, emotional, autonomic rxns to pain

Question 5

dorsal spinocerebellar tract vs cuneocerebellar tract vs ventral spinocerebellar tract

Answer 5

unconscious proprioception from T1-L2 => Clarke’s column in intermediate zone vs unconscious proprioception of UE from accessory cuneate nucleus next to cuneate nucleus proper in med vs in dorsal horn & intermediate zone –> bil enter sup cerebellar peduncle to ipsi sensation; monitors amt of gray interneuron activity

Question 6

rubrospinal tract

Answer 6

red nucleus in midbrain –> contralat spinal cord –> excite motor neurons in UE prox limb flexors. cerebellar output from sup cerebellar peduncle synapse w/ contralat red nucleus in loop w/ inf olive & cerebellar nuclei

Question 7

2 tracts carry output for GPi: lenticular fasciculus vs ansa lenticularis

Answer 7

from dorsal GPi and medially thru post limb of internal capsule vs from ventral GPi and loops anteriorly to internal capsule. both form thalamic fasciculus projecting to ventral ant nucleus of thal