Anatomy - PCML Flashcards

1
Q

where do fibers from the DRG go into the spinal cord in PCML

A

posterior horn

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2
Q

large-diameter fibers relay what kind of info

A

touch, flutter, vibrations, proprioception

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3
Q

how do fibers of PCML enter the spinal cord

A

via medial division of posterior root

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4
Q

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

A

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

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5
Q

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

A

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

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6
Q

describe the topographical organization of the posterior columns

A

from medial to lateral:

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

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7
Q

what makes up the fasciculus gracile

A

sacral and coccygeal levels, lumbar and thoracic levels below T6

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8
Q

what makes up the fasciculus cuneatus

A

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

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9
Q

spinal cord lesions of the PCML result in ____

A

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

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10
Q

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

A

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

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11
Q

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

A

the core clusters receive inputs from rapidly and slowly adapting afferents

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

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12
Q

describe the tract of the PCML once it hits the medulla

A

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

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13
Q

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

A

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

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14
Q

where does the medial leminiscus terminate in the PCML

A

the ventral posterolateral nucleus (VPL)

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15
Q

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

A

spinal cord: posterior spinal a.

medulla: anterior spinal a.

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16
Q

brainstem lesions of the PCML result in ______

A

contralateral loss of discriminative touch, vibratory, and positional sensibilities

17
Q

where are the VPL and VPM located

A

in the caudal thalamus

18
Q

what is the blood supply to the VPL and VPM

A

thalamogeniculate arteries from the posterior cerebral a.

19
Q

what separates the VPL and VPM

A

fibers of the arcuate lamina

20
Q

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

A

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

21
Q

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

A

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

22
Q

what is the blood supply to the primary somatosensory cortex

A

anterior and middle cerebral arteries

23
Q

compare the effects of MCA and ACA lesions

A

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

24
Q

what are Brodmann areas

A

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

25
Q

describe the locations of Brodmann areas

A

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

26
Q

what inputs does the secondary somatosensory cortex receive

A

from ipsilateral primary somatosensory cortex and VPI of thalamus

27
Q

where is the secondary somatosensory cortex

A

inside the lateral sulcus

28
Q

what are the parietal cortical regions

A

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

29
Q

lesions in the parietal cortical regions cause what

A

agnosia (inability to interpret sensations and hence to recognize things)

  • contralateral body parts are lost from personal body map
  • not recognizing limbs
30
Q

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

A

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