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PNB 2XB3 - Midterm 2: Somatosensory Questions with 100% Correct Answers | Latest Update | Verified
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  • PNB 2XB3 : Somatosensory

DCML - 1) mechanosensory receptors send info to fibers in gracile & cuneate pathways 2) fibers travel to caudal medulla, synapse at dorsal column nucleus (and switch sides) 3) exit DCN as arcuate fibers, cross the midline to form medial lemniscus carries through pons, midbrain, brainstem 4) syn...

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  • September 17, 2024
  • 7
  • 2024/2025
  • Exam (elaborations)
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  • pnb 2xb3 somatosensory

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  • PNB 2XB3 : Somatosensory
  • PNB 2XB3 : Somatosensory

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PNB 2XB3 - Midterm 2: Somatosensory
DCML - 1) mechanosensory receptors send info to fibers in gracile & cuneate pathways

2) fibers travel to caudal medulla, synapse at dorsal column nucleus (and switch sides)

3) exit DCN as arcuate fibers, cross the midline to form medial lemniscus carries through pons, midbrain,
brainstem

4) synapse at thalamus (VPL)

5) internal capsule takes axons to post-central gyrus/S1, some to S2.




Meissener - - rapidly adapting

-40% of mechanosensory innervation in hand

- skin motion, indentation, low frequency vibrations for textured objects***

- more than 4x more sensitive than Merkell to skin deformation, but larger receptive fields so less spatial
resolution

- ie. tea set plate etching



Pacinian - - rapidly adapting

- high frequency vibration **

- ie. tool use, vibrations up your arm



Ruffini - - slowly adapting

- skin stretch



Dermatome - innervation rising from a single dorsal root ganglion on the spinal nerve



is the overlap of dermatones more extensive for touch or pain/temp - more overlap in touch



gracile tract - for DCML, bundle of fibers from lower limbs that travel most medial

, Merkell cells - - slowly adapting

- 25% of mechanosensory afferents in hand

- highest spatial resolution

- edges, points, corners, curvature

- static indentation **



cuneate tract - for DCML, bundle of fibers from upper limbs/neck/trunk that lie more lateral



post-synaptic dorsal column projection - projection neurons in dorsal horn laminae III, IV, and V
receive mechanosensory input and project parallel through dorsal column to dcn



decussation of the medial lemniscus - crossing of internal arcuate fibers




VPM of thalamus - receives information from trigeminal lemniscus that carreis info from face
(more medially located)

- part of ventral posterior complex



S1 subdivision: 3a - proprioceptive



S1 subdivision: 3b - light touch; v small receptive fields



S1 subdivision: 1 - light touch; larger receptive fields



S1 subdivision: 2 - proprioceptive & light touch



lesions in 3b - defecits in all tactile sensations

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