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Flashcards in Anatomy - PCML Deck (30)
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where do fibers from the DRG go into the spinal cord in PCML

posterior horn


large-diameter fibers relay what kind of info

touch, flutter, vibrations, proprioception


how do fibers of PCML enter the spinal cord

via medial division of posterior root


once in the spinal cord where do fibers of the PCML go

synapse onto second order neurons at, above, or below level of entry


the largest set of branches of PCML from the DRG do what once in the spinal cord

ascend cranially to form the fasciculus gracilis or fasciulus cuneatus (posterior/dorsal columns)


describe the topographical organization of the posterior columns

from medial to lateral:

sacral/coccygeal levels --> lumbar and thoracic levels below T6 --> thoracic levels above T6 --> low cervical levels --> upper cervical levels


what makes up the fasciculus gracile

sacral and coccygeal levels, lumbar and thoracic levels below T6


what makes up the fasciculus cuneatus

thoracic levels above T6, lower cervical, and upper cervical levels


spinal cord lesions of the PCML result in ____

ipsilateral loss of discriminative, positional, and vibratory tactile sensations at or below the level of injury


if patient has a wide based stance and is placing feet to the floor with force, what might you susepct

damage to PCML (they are trying to create the missing proprioceptive input)


describe the segregation of tactile inputs within the nuclei gracile and nuclei cuneatus and also the VPL

the core clusters receive inputs from rapidly and slowly adapting afferents

the outer shells receive input from muscle spindles, joints, and pacinian corpuscles


describe the tract of the PCML once it hits the medulla

the axons cross in the medulla as internal arcuate fibers and then ascend as the medial leminiscus to the thalamus contralateral to where the fibers originated in the spinal cord


how does the organization of the upper and lower extremities change in the pons for the PCML

as the medial leminiscus ascends it rotates laterally in the pons which causes the upper extremity fibers to lie medially and the lower extremity fibers to lie laterally


where does the medial leminiscus terminate in the PCML

the ventral posterolateral nucleus (VPL)


what is the arterial supply for the PCML in the spinal cord and then once its gets to the medulla

spinal cord: posterior spinal a.
medulla: anterior spinal a.


brainstem lesions of the PCML result in ______

contralateral loss of discriminative touch, vibratory, and positional sensibilities


where are the VPL and VPM located

in the caudal thalamus


what is the blood supply to the VPL and VPM

thalamogeniculate arteries from the posterior cerebral a.


what separates the VPL and VPM

fibers of the arcuate lamina


what is the main type of neuron in the VPL and what do they do

third order neurons that leave the VPL, traverse the posterior limb of internal capsule, and terminate in primary and secondary somatosensory cortices


what is the minor type of neuron in the VPL and what do they do

local circuit interneurons that moderate the frequency at which information is relayed to the cortex by other third order neurons


what is the blood supply to the primary somatosensory cortex

anterior and middle cerebral arteries


compare the effects of MCA and ACA lesions

MCA: tactile loss over contralateral upper body and face
ACA: contralateral lower limb


what are Brodmann areas

subdivisions of the primary somatosensory cortex on the postcentral gyrus
- anterior to posterior: 3a, 3b, 1, 2


describe the locations of Brodmann areas

3a: in the depths of the central sulcus
3b an 1: extend up back of sulcus onto shoulder of posctentral gyrus
2: lies on gyral surface


what inputs does the secondary somatosensory cortex receive

from ipsilateral primary somatosensory cortex and VPI of thalamus


where is the secondary somatosensory cortex

inside the lateral sulcus


what are the parietal cortical regions

another cortical somatosensory region; receives tactile inputs; located posterior to the primary somatosensory cortex


lesions in the parietal cortical regions cause what

agnosia (inability to interpret sensations and hence to recognize things)
- contralateral body parts are lost from personal body map
- not recognizing limbs


what is the function of the afferent cerebellar pathway (spinocerebellar)

transmits proprioceptive and limited cutaneous info to the cerebellum
- info about limb position, joint angles, muscle tension