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Neuro-E2 > somatosensory pathways > Flashcards

somatosensory pathways Flashcards

1
Q

Posterior column-medial lemniscal system (PCMLS)

A

perception and appreciation of mechanical stimuli
conscious awareness of body position and limb
movement in space

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2
Q

two-point discrimination

A

ability to discriminate between two separate stimuli simultaneously
related to density of peripheral nerve endings

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3
Q

where can you find a high density of peripheral receptors

A

digits and perioral region

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4
Q

where can you find a low density of peripheral receptors

A

back

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5
Q

what is a receptive field

A

area of skin innervated by a somatic afferent fiber

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6
Q

how do primary sensory fibers enter the spinal cord

A

via medial division of the posterior root

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7
Q

where can you see the fasciculus cuneatus

A

above T6 (lateral to fasciculus gracilis)

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8
Q

SC lesion of Fasciculi gracilis and cuneatus

A

ipsilat. reduction or loss of discriminative touch, vibration, positional sense at and below level of injury

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9
Q

where are the second order neurons of the PCMLS?

A

gracile and cuneatus nuclei – posterior medulla

input from ipsilat. DRG

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10
Q

what is the segregation of tactile inputs in the nuclei

PCMLS

A

core clusters: inputs from rapidly and slowly adapting
afferents
outer shells: muscle spindles, joints, pacinian
corpuscles

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11
Q

when do the internal arcuate fibers of the second order neurons become the medial lemniscus
(PCMLS)

A

after sensory decussation in the medulla

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12
Q

where are the third order neurons of the PCMLS

A

VPL (ventral posterolateral nucleas)

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13
Q

damage @ brainstem causes

PCMLS

A

loss of discriminative touch, vibration, positional sense of contralat. side

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14
Q

what comprises the ventral posterior nuclei

what separates them

A

ventral posterolateral nucleas (VPL) – receives PCMLS
ventral posteromedial nucleas (VPM) – receives
trigeminal sensory info

separated by arcuate lamina

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15
Q

blood supply to ventral posterior nucleas

A

thalamogeniculate branches of posterior cerebral a

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16
Q

compromise of thalamogeniculate branch of PCA can cause

A

loss of all tactile sensation on contralat. body and head

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17
Q

VPL receives input from

A

medial lemniscus (PCMLS) fibers from contralat. nucleas cuneatus and nucleas gracile

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18
Q

populations of neurons in VPL

A

third order neurons – travel along posterior limb of IC
to get to primary and secondary somatosensory
cortices
local circuit interneurons (inhibitory)

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19
Q

blood supply to primary somatosensory cortex (SI)

A

both ACA and MCA

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20
Q

MCA lesion –>

A

loss of tactile sense over contralat. face and upper body

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21
Q

ACA lesion –>

A

loss of tactile sense over contralat. lower limb

22
Q

SI divisions from ant –> post

A

3a, 3b, 1, 2

23
Q

lesion of parietal cortical region

A

can produce agnosia
sensory not affected too much, but contra lat limbs
no longer on body map. not recognized as part of
own body

24
Q

trigeminal nuclei (4) and f(x)

A

main sensory nucleas – touch and pressure
trigeminal motor nucleas – m of mastication
spinal nucleas – pain and temp
mesencephalic nucleas – proprioceptive afferents of
TMJ and masticatory m

25
Q

Main sensory nucleas divisions

A

dorsomedial division: afferent input from oral cavity

ventrolateral division: afferents from V1, V2, V3

26
Q

2nd order fibers of ventrolateral division follows what tract

A

anterior trigeminothalamic tract –> contralat. VPM

–posterior limb of IC–> SI

27
Q

2nd order fibers of dorsomedial division follow what tract

A

posterior trigeminothalamic tract –> ipsilat. VPM

–posterior limb of IC–> SI

28
Q

somatotropic arrangement of VPM

A 
medial = oral cavity input
lateral = external face input
29
Q

what classification of neurons is the mesencephalic nucleas comprised of

A

psuedounipolar neurons

30
Q

jaw jerk reflex

A

stretching masseter m causes it to contract bilat.
mesencephalic nucleas –> trigem. motor nucleas –>
masseter m
intensity enhanced w/ UMN lesion

31
Q

cross sensory syndrome/findings

brainstem? SC?

A

brainstem or sc lesions that result in deficits that differ on either side of the body
brainstem: sensory deficit contralat. trunk/extremities
sensory deficit ipsilat. face
SC: proprioceptive defecit one side, anesthesia other

32
Q

SI lesions can lead to

A

loss of proprioception, position sense, vibratory sense, pain, temp on contralat. side

33
Q

lesion in area 1 of SI –>

A

loss of texture discrimination

34
Q

lesion in area 2 of SI –>

A

loss of shape and size discrimination

35
Q

lesion in area 3b of SI –>

A

loss of texture, shape, and size discrimination

36
Q

modalities of sensation conveyed by anterolateral system (ALS)

A

nondiscriminative touch, pain, temp

37
Q

ALS (spinothalamic) pathway

A

body –> thalamus –> somatosensory and limbic cortices

similar to anterior trigeminothalamic tract, but from body not face/head

38
Q

disruption of ALS pathway produces

A

numbness, tingling, parasthesia, anesthesia

39
Q

how do cutaneous nociceptors and primary neurons enter the spinal cord

A

lateral division of the posterior root entry zone travel in posterolateral fasciculus

40
Q

direct ALS pathway

spinothalamic

A

(nondistinctive tactile, pain, temp)
enters SC at posterolateral fasciculus and bifurcates
ascending branches synapse on posterior horn
axons decussate via anterior white commisure
travel through lateral spinothalamic tract on
contralat. side
travel to VPL in thalamus

41
Q

fate of descending branches of direct ALS pathway

A

synapse with interneurons in gray matter to contribute segmental spinal reflexes

42
Q

indirect ALS pathway

spinothalamic

A

(noxious and innocuous mechanical and temp info to reticular formation)
similar pathway as direct, but third order neurons in reticular formation of brainstem take signal to medial thalamic nuclei

synapse in lamina 2&3 of posterior horn to influence cells in 5 to 8

43
Q

somatotropic arrangement of ALS

A

axons from lower levels are more posterolateral

higher levels are added anteromedially

44
Q

blood supply of ALS

A

originates from arterial vasocorona and via sulcal brances of anterior spinal a

45
Q

occlusion of vessels supplying ALS results in

A

patchy nociception, thermal and nondistinctive touch over contralat. side of body

anterolateral cordotomy = complete loss of these

46
Q

hemisection of the SC (brown-sequard syndrome)

A

contralat. loss of pain and temp (ALS)
ipsilat. loss of discriminative tactile, vibratory, positional
sensation @ and below level (PCMLS)

47
Q

syringomyelia effects on somatosensory pathways

A

impinge on AWC
bilat. loss of nondiscriminative tactile, pain, temp
seen 2 levels down?

48
Q

effect of vascular lesions/tumors in lower brainstem on sensory modalities (medullary ALS fibers)

A

dissociated sensory loss: deficit of one modality with the other modality within normal limits
ALS: i.e. deficit of pain/temp, normal
vibration/discriminitive touch or vice versa
i.e. PCMLS and ALS stay separate

49
Q

where are medullary ALS fibers positioned

A

near anterolateral surface, anterior to spinal trigeminal nucleas

remains separated from PCMLS

50
Q

divisions of the spinal trigeminal tract

A

pars oralis, pars interpolaris, pars caudalis(pain and temp procession for face and head)

51
Q

how far does the spinal trigeminal tract extend

A

pontomedullary jxn to 3rd cervical segment

52
Q

f(x) of pars caudalis

A

allows for smooth transition of cutaneous info from posterior head (spinal) with cutaneous anterior face/head (brainstem)

Neuro-E2 (12 decks)

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