Neuro 7 Somatosensory

Front 1

what does somatosensory refer to

Back 1

sensations of touch, pain, temperature, vibration, and proprioception

Front 2

What does the posterior column-medial lemniscal pathway convey

Back 2

proprioception, vibration sense, and fine discriminative touch

Front 3

What does the anterolateral pathway convey

Back 3

pain, tmperature sense, and crude touch

Front 4

conduction velocity of small vs large and mylinated vs unmylinated

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large faster-diameter mylinated axons conduct faster than smaller diameter unmyelinated axons

Front 5

where are sensory neuron cell bodies

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dorsal root ganglia

Front 6

type of axons of neurons in dorsal root ganglia

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stem axon that bifurcates resulting in one long process that conveys sensory information from the periphery and a second that carries info into spinal cord

Front 7

peripheral region innervated by sensory fibers from a single nerve root level

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dermatome

Front 8

somatotopic organization of posterior column

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as fibers asend, supior structures add on making lower sensory fibers more medial

Front 9

where do many of the posterior column axons ascend to

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ipsilateral to posterior column nuclei in medulla; axon collaterals also enter spinal cord gray matter and synapse onto interneurons and motor neurons

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gracile fasciculus

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medial portion that carries info from legs and lower trunk

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cuneate fasciculus

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lateral that carries info from upper trunk above ~T6 and from arms and neck

Front 12

where do first order neurons in gracile and cuneate fasciculi synapse

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2nd order neurons in nucleus gracilis and nucleus cuneatus in lower medulla

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where do axons of second order neurons decussate (cross)

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as internal arcuate fibers and then form medial lemniscus on the other side of the medulla

Front 14

orientation of medial lemniscus

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initially vertical, then progressively more lateral and inclined as it ascends in the brainstem

Front 15

where do secondary neurons of posterior column synapse

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ventral posterior lateral nucleus (VPL) of the thalamus

Front 16

Where do axons from VPL go

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project through the posterior limb of the internal capule in the thalamic somatosensory radiations to reach the primary somatosensory cortex

Front 17

What pathway conveys touch sensation for the face

Back 17

trigeminal lemniscus

Front 18

pathway of trigeminal lemniscus

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ventral posterior medial nucleus (VPM) to somatosensory cortex

Front 19

What cortical layer do synaptic inputs to the primary somatosensory cortex from both the face and body occur

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cortical layer IV mostly and deeper portions of layer III

Front 20

smaller diameter unmylinated axons carring pain and temp info enter spinal cord via dorsal root ganglia and go where

Back 20

synapse immediately in gray matter of spinal cord

Front 21

where in the spinal cord do these axons synapse

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mainly dorsal horn marginal zone (lamina I), and deeper in dorsal horn (lamina V)

Front 22

Lissauer's tract

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tract where fibers ascend or descend before entering gray matter

Front 23

Where do axons from 2nd order sensory neurons in the central gray cross over

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spinal cord anterior (ventral) commissure)

Front 24

where do the 2nd order axons ascend once crossing over in the spinal cord

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anterolateral white matter; takes 2 or 3 segments for decussating fibers to reach opposite side

Front 25

lateral cord lesion will affect contralateral pain and temperature beginning where

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a few segments below the level of lesion

Front 26

somatotopic organization of anterolateral pathways

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feet most laterally represented; fibers added on medially as they ascend

Front 27

where are anterolateral pathways located when they reach the medulla

Back 27

laterally, running in the groove btwn the olives and the inferior cerebral peuncles

Front 28

where do axons of anterolateral pathways go after medulla

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enter pontine tegmentum to lie just lateral to the medial lemniscus in the pons and midbrain

Front 29

where do the 2nd order axons of the anterolateral pathways synapse

Back 29

thalamus, which project via thalamic somatosensory radiations to primary somatosensory cortex

Front 30

whar carries pain and temp sensation for the face

Back 30

trigeminothalamic tract; similar to anterolateral pathway

Front 31

three tracts in the anterolateral pathway

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spinothalamic, spinoreticular, and spinomesencephalic tracts

Front 32

which tract mediates discriminative aspects of pain and temperature sensation such as location and intensity of stimulus

Back 32

spinothalamic tract

Front 33

main relay for the spinothalamic tract

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VPL of the thalamus is main relay; also intralaminar thalamic nuclei (central lateral nucleus) and medial thalamic nuclei (mediodorsal nuclei)

Front 34

where does the spinoreticular tract terminate

Back 34

on medullary-pontine reticular formation-projects to the intralaminar thalamic nuclei

Front 35

where do the intralaminar thalamic nuclei project

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diffusely to the entire cerebral cortex (thought to be involved in behavioral arousal)

Front 36

where does the spinomesencephalic tract project

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to midbrain periaqueductal gray matter and the superior colliculi

Front 37

periaqueductal gray matter participates in

Back 37

central modulation of pain

Front 38

What spinal cord laminae do the spinothalamic and spinomesencephalic tracts mainly arise from

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cord laminae I and V

Front 39

What spinal cord laminae does the spinoreticular tract mainly arise from

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diffusely from intermediate zone and ventral horn laminae 6-8

Front 40

Brodmann areas of primary somatosensory cortex

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3, 1, 2

Front 41

somatotopic organization of primary sensory cortex

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face lateral and leg medial

Front 42

where is info from the primary somatosensory cortex conveyed

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secondary somatosensroy association cortex within the sylvian fissure (parietal operculum)

Front 43

where does further processing of somatosensory info occur

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association cortex of posterior parietal lobe (brodman's areas 5 and 7)

Front 44

when does cortical sensory loss occur

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lesions of somatosensory cortex and adjacent regions

Front 45

what does pain modulation involve

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interactions btwn local circuits at level of spinal cord dorsal horn and long-range modulatory inputs

Front 46

gate control theory

Back 46

sensory inputs from large diameter non-pain A-Beta fibers reduce pain transmission through the dorsal horn

Front 47

what does the periqueductal gray receive inputs from

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hypothalamus, amygdala, and cortex

Front 48

what does periaqueductal gray do

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inhibits pain transmission in the dorsal horn via the rostral ventral medulla (RVM)

Front 49

where is the RVM

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pontomedullary jxn

Front 50

what neurons does the RVM have

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serotoneurgic (5-HT) neurons of the raphe nuclei

Front 51

what do the serotoneurgic nerons do

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project to the spinal cord and modulate pain in the dorsal horn

Front 52

what does substance P do to the RVM

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causes it to send inputs to the locus ceruleus-which sends noradrenergic projections to modulate pain in the spinal cord dorsal horn

Front 53

divisions of the thalamus

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medial nuclear group, lateral nuclear group, and anterior nuclear group

Front 54

what divided the thalamus into these regions

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Y-shaped white matter structure called internal medullary lamina

Front 55

intralaminar nuclei

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nuclei within the internal medullary lamina

Front 56

midline thalamic cuclei

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additional collection of nuclei adjacent to the third ventricle; several continuous with and similar to the intralaminar nuclei

Front 57

thalamic reticular nucleus

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extensive, but thin sheet enveloping the lateral aspect of the thalamus

Front 58

Three main categories of thalamic nuclei

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1) relay 2) intralaminar 3) reticular

Front 59

relay nuclei

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most of thalamus; receive inputs and project to cortex - localized and diffuse distributions

Front 60

what information is relayed in the lateral geniculate nucleus (LGN)

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visual

Front 61

what information is relayed in the medial geniculate nucleus (MGN)

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auditory

Front 62

mnemonic for LGN and MGN

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lateral light and medial music

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anterior nuclear group projects to

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limbic pathways in cortex (anterior cingulate cortex)

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pulvinar

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large, pillow-shaped nucleus that occupies most of the posterior thalamus

Front 65

mediodorsal nucleus (MD)

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major thalamic relay for frontal association cortec

Front 66

intralaminar nuclei receive main inputs and outputs from

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basal ganglia

Front 67

two functional regions of intralaminar nuclei

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caudal intralaminar nuclei and rostral intralaminar nuclei

Front 68

what are caudal intralaminar nuclei involved in

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basal ganglia circuitry

Front 69

rostal intralaminar nuclei are involved in

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basal ganglia input/output; also ascending reticular activating systems (ARAS) to the cortex

Front 70

reticular nucleus location

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thin sheet just lateral ro the rest of thalamus and just medial to internal capsule; doesn't project to cortex

Front 71

what inputs does the reticular nucleus receive

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from other thalamic nuclei and cortex and projects back to thalamus

Front 72

what neurons make up most of the reticular nucleus

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inhibitory GABAergic neurons

Front 73

paresthesias

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abnormal positive sensory phenomenon

Front 74

presentation of posterior column-medial lemniscal pathways lesions

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tingling, numb sensation, feeling of a tight band around trunk or limbs, sensation of gauze on fingers when touching objects

Front 75

presentation of anterolateral pathways lesions

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sharp, burning, or searing pain

Front 76

lesions of parietal lobe

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contralateral numb tingling, pain can be prominent

Front 77

lesions of thalamus

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severe contralateral pain (Dejerine-Roussy syndrome)

Front 78

lesions of c-spine

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Lhermitte's sign-electricity like sensation running down back into extremities upon neck flexion

Front 79

lesions of nerve roots often produces

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radicular pain that radiates down limb in a dermatomal distribution; numbness and tingling

Front 80

dysesthesia

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unpleasant, abnormal sensation

Front 81

hyperpathia or allodynia

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painful sensations provoked by minor stimuli such as light touch

Front 82

lateral pons or lateral medulla lesion

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involves anterolateral pathways and spinal trigeminal nucleus on same side; loss pain/temp contralateral body; pain/temp ipsilateral face

Front 83

midial medulla lesion

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involves medial lemniscus causing contralateral loss vibration/joint position sense

Front 84

common causes of transverse spinal cord lesion

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trauma, tumors, multiple sclerosis, transverse myelitis

Front 85

hemicord lesions (Brown-Sequard syndrome)

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ipsilateral UMN-type weakness (corticospinal), ipsilateral loss vibration and joint position sense (posterior columns), contralateral loss pain and temp (anterolateral systems)

Front 86

common causes of hemicord lesions (Brown-Sequard syndrome)

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penetrating injuries, MS, lateral compression from tumors

Front 87

central cord syndrome in small lesions

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bilateral regions of suspended sensory loss to pain and temp (spinothalmic fibers)

Front 88

central cord lesion distribution in c-spine lesions

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cape distribution

Front 89

central cord syndrome in larger lesions

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anterior horn cells damaged producing LMN deficits, UMN deficits (corticospinal), posterior columns may be involved; sacral sparing

Front 90

common causes of central cord syndrome

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spinal cord contusion, posttraumatic syringomyelia, intrinsic spinal cord tumors (hemangioblastoma), ependymoma, astrocytoma

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posterior cord syndrome

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loss of vibration and position sense below lesion

Front 92

what can occur with large posterior cord syndrome lesions

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encroachment on lateral corticospinal tracts

Front 93

common causes of posterior cord syndrome

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trauma, extrinsic compression from posteriorly located tumors, MS; vit B12 deficiency and tabes dorsalis affect posterior cord

Front 94

anterior cord syndrome

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loss of pain and temp sense (anterolateral pathways), LMN weakness (anterior horn cell damage)

Front 95

what is involved with larger anterior cord syndrome lesions

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corticospinal tracts causeing UMN signs

Front 96

what symptom is common in anterior cord syndrome

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incontinence-descending pathways controlling sphincter fxn tend to be more ventrally located

Front 97

common causes of anterior cord syndrome

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trauma, MS, anterior spinal artery infarct

Front 98

sensory info from rectum, bladder, urethra, and genitalia is via sacral nerve roots

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S2-4

Front 99

where do voluntary somatic motor fibers arise that control pelvic floor muscles

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anterior horn cells of S2-4

Front 100

where do sympathetics arise for bladder intervation

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intermediolateral cell column at T11 to L1

Front 101

bilateral pathways are involved in

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lesions that affect bowel, bladder, or sexual fxn

Front 102

detrusor reflex is mediated by

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intrinsic spinal cord circuits regulated by pontine micturition center and possibly cerebellar and basal ganglia pathways

Front 103

micturition

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initialed by voluntary relaxation of external sphincter, triggers inhibition of sympathetics to bladder neck causing relaxation, acitvation of parasympathetics causing detrusor contraction

Front 104

urethral reflex

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urethral sphincter contration triggers detrusor relaxation

Front 105

lesions affecting bilateral medial frontal micturation centers result in

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reflex activation of pontine and spinal micturition centers when bladder is full

Front 106

common causes of frontal-type incontinence

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hydrocephalus, parasagittal meningioma, bifrontal glioblastoma, traumatic brain injury, neurodegenerative disorders

Front 107

lesions below pontine micturation center and above conus medullaris levels S2-4

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initially cause flaccid, acontractile bladder--then over weeks/months into hyperreflexive bladder

Front 108

common spinal cord lesions causing acontractile or hyperreflexic bladder

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trauma, tumors, transverse myelitis, MS

Front 109

Lesion of the peripheral nerves or spinal cord at S2-4

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flaccid areflexic bladder; due to loss of parasympathetic outflow to detrusor and/or loss afferent sensory info from bladder and urethra

Front 110

common causes of Lesion of the peripheral nerves or spinal cord at S2-4

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diabetic neuropathy and compression of conus medullaris or cauda equina by trauma, tumor, disc herniation

Front 111

What else can cause urinary incontinence and retention

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prostatic hypertrophy, urethral strictures, intrinsic sphincter deficiency

Front 112

what origin do desending pathways controlling fecal continence have

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medial frontal lobes

Front 113

internal smooth muscle sphincter innervation

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sacral parasympathetics

Front 114

external striated muscle sphincter innervation

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pelvic nerves arising from Onuf's nucleus

Front 115

pelvic floor muscle innervation

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sacral anterior horn cells

Front 116

what does GI motility depend on

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parasympathetics from S2-4 for colorectal smooth muscle beyond splenic flexture; above flexture parasympathetic from vagus

Front 117

what can fecal incontinence be caused by

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diffuse cerebral or midial frontal lesions, spinal cord lesions, lesions of sacral nerve roots or pelvic or pudendal nerves

Front 118

what occurs in acute spinal cord lesions

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anal sphincter is completely flaccid; loss of parasympathetic outflow causing severe constipation

Front 119

sensation from genetalia is via

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pudendal nerve reaching to S2-4

Front 120

what mediates female secretion of lubricating mucus by Bartholin's glands

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parasympathetics

Front 121

what mediates female increases in vaginal blood flow and secretions

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sympathetics

Front 122

ejaculation is mediated via

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sympathetics - contraction of smooth muscle

Front 123

what can cause sexual dysfunction

Back 123

peripheral nerve lesions, higher-order cortical lesions, and psychological factors