L07 Rosales Somatosensory System Flashcards
anterolateral system
Comprises the lateral (pain/temp) and anterior (light touch, pressure) spinothalamic tracts.
medial lemniscal pathway
Comprises the dorsal column: pressure, discriminative touch, vibration, conscious proprioception. Cuneate and Gracile fasciculi ascend ipsilaterally and synapse in the cuneate and gracile nuclei in the medulla. The nuclei send fibers that decussate (via the internal arcuate fibers) and then ascend contralaterally in the medial lemniscus to the thalamus.
spinocerebellar pathway
Comprises posterior and anterior spinocerebellar tracts (unconscious proprioception).
descending branch of the trigeminal pathway
Facial pain/temp. 1: CN V ganglion sends fibers to the pons that either ascend or descend: descending fibers form the spinal trigeminal tract and synapse throughout the 2: spinal trigeminal nucleus. STN fibers decussate then ascend as trigeminothalamic tract to 3: VPM of thalamus and then through the posterior limb of the internal capsule to the post-central gyrus.
ascending branch of the trigeminal pathway
Facial conscious proprioception, discriminative touch, vibration. 1: CN V ganglion sends fibers to the pons that either ascend or descend: ascending fibers synapse in the 2: principle nucleus of V, whose fibers decussate and then form the trigeminothalamic tract, which synapses in the 3: VPM of thalamus and then ascend in the posterior limb of the internal capsule to the postcentral gyrus.
outline the unconscious proprioception component of the trigeminal pathway
1: CN V ganglion receptors synapse in the 2: mesencephalic nucleus of V. These axons form the mesencephalic tract of V and travel bilaterally to the 3: motor nuclei of V, then the 4: reticular formation and the 5: cerebellum.
Which senses uses unencapsulated nerve endings?
Pain/temp, pressure, itch
Which part of the spinal cord secretes substance p?
Rexed’s lamina II, aka substantia gelatinosa
Which of Rexed’s lamina is involved with the spinocerebellar tracts?
Rexed’s lamina VII, aka dorsal nucleus of Clarke
fasciculus gracilis
SOURCE: Leg. CARRIES: conscious proprioception, epicritic discrimination, and vibration. LOCATION: dorsal column, L5-C1. PATH: Ascends ipsilaterally, synapses in nucleus gracilis, decussates and ascends in medial lemnisus to VPL of thalamus, then goes to post-central gyrus.
fasciculus cuneatus
SOURCE: Arm. CARRIES: conscious proprioception, epicritic discrimination, and vibration. LOCATION: dorsal column, T6-C1. PATH: Ascends ipsilaterally, synapses in nucleus cuneatus, decussates and ascends in medial lemnisus to VPL of thalamus, then goes to post-central gyrus.
lateral spinothalamic tract
CARRIES: pain/temp. 1ST: dorsal root ganglion. 2ND: dorsal horn; decussates within 1-2 segments via the anterior white commissure then ascends contralaterally (in lateral spinothalamic tract). 3RD: VPL of thalamus to sensory cortex.
ventral spinothalamic tract
CARRIES: touch, pressure. 1ST: dorsal root ganglion, ascends or descends ipsilaterally. 2ND: dorsal horn. Decussates via the anterior white commissure then ascends contralaterally (in anterior spinothalamic tract). 3RD: VPL of thalamus to sensory cortex.
dorsal spinocerebellar tract
CARRIES: unconscious proprioception. 1ST: dorsal root ganglion, enters spinal cord via dorsal rootlets. 2ND: nucleus dorsalis (clark’s column in lamina VII); ascends IPSILATERALLY via dorsal spinocerebellar tract and passes through inferior cerebellar peduncle to cerebellar cortex.
ventral spinocerebellar tract
CARRIES: unconscious proprioception, fine touch, vibration. 1ST: dorsal root ganglion, enters spinal cord via dorsal rootlets. 2ND: nucleus dorsalis (clark’s column in lamina VII); MOST fibers cross and ascend CONTRALATERALLY via ASCT and pass through superior cerebellar peduncle, where most will RECROSS back through the middle cerebellar peduncles. SOME fibers remain uncrossed and ascend IPSILATERALLY in ASCT, entering the superior cerebellar peduncle to synapse on the cerebellar cortex.
