Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
123 Cards in this Set
- Front
- Back
what does somatosensory refer to |
sensations of touch, pain, temperature, vibration, and proprioception
|
|
What does the posterior column-medial lemniscal pathway convey
|
proprioception, vibration sense, and fine discriminative touch
|
|
What does the anterolateral pathway convey
|
pain, tmperature sense, and crude touch
|
|
conduction velocity of small vs large and mylinated vs unmylinated
|
large faster-diameter mylinated axons conduct faster than smaller diameter unmyelinated axons
|
|
where are sensory neuron cell bodies
|
dorsal root ganglia
|
|
type of axons of neurons in dorsal root ganglia
|
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
|
|
peripheral region innervated by sensory fibers from a single nerve root level
|
dermatome
|
|
somatotopic organization of posterior column
|
as fibers asend, supior structures add on making lower sensory fibers more medial
|
|
where do many of the posterior column axons ascend to
|
ipsilateral to posterior column nuclei in medulla; axon collaterals also enter spinal cord gray matter and synapse onto interneurons and motor neurons
|
|
gracile fasciculus
|
medial portion that carries info from legs and lower trunk
|
|
cuneate fasciculus
|
lateral that carries info from upper trunk above ~T6 and from arms and neck
|
|
where do first order neurons in gracile and cuneate fasciculi synapse
|
2nd order neurons in nucleus gracilis and nucleus cuneatus in lower medulla
|
|
where do axons of second order neurons decussate (cross)
|
as internal arcuate fibers and then form medial lemniscus on the other side of the medulla
|
|
orientation of medial lemniscus
|
initially vertical, then progressively more lateral and inclined as it ascends in the brainstem
|
|
where do secondary neurons of posterior column synapse
|
ventral posterior lateral nucleus (VPL) of the thalamus
|
|
Where do axons from VPL go
|
project through the posterior limb of the internal capule in the thalamic somatosensory radiations to reach the primary somatosensory cortex
|
|
What pathway conveys touch sensation for the face
|
trigeminal lemniscus
|
|
pathway of trigeminal lemniscus
|
ventral posterior medial nucleus (VPM) to somatosensory cortex
|
|
What cortical layer do synaptic inputs to the primary somatosensory cortex from both the face and body occur
|
cortical layer IV mostly and deeper portions of layer III
|
|
smaller diameter unmylinated axons carring pain and temp info enter spinal cord via dorsal root ganglia and go where
|
synapse immediately in gray matter of spinal cord
|
|
where in the spinal cord do these axons synapse
|
mainly dorsal horn marginal zone (lamina I), and deeper in dorsal horn (lamina V)
|
|
Lissauer's tract
|
tract where fibers ascend or descend before entering gray matter
|
|
Where do axons from 2nd order sensory neurons in the central gray cross over
|
spinal cord anterior (ventral) commissure)
|
|
where do the 2nd order axons ascend once crossing over in the spinal cord
|
anterolateral white matter; takes 2 or 3 segments for decussating fibers to reach opposite side
|
|
lateral cord lesion will affect contralateral pain and temperature beginning where
|
a few segments below the level of lesion
|
|
somatotopic organization of anterolateral pathways
|
feet most laterally represented; fibers added on medially as they ascend
|
|
where are anterolateral pathways located when they reach the medulla
|
laterally, running in the groove btwn the olives and the inferior cerebral peuncles
|
|
where do axons of anterolateral pathways go after medulla
|
enter pontine tegmentum to lie just lateral to the medial lemniscus in the pons and midbrain
|
|
where do the 2nd order axons of the anterolateral pathways synapse
|
thalamus, which project via thalamic somatosensory radiations to primary somatosensory cortex
|
|
whar carries pain and temp sensation for the face
|
trigeminothalamic tract; similar to anterolateral pathway
|
|
three tracts in the anterolateral pathway
|
spinothalamic, spinoreticular, and spinomesencephalic tracts
|
|
which tract mediates discriminative aspects of pain and temperature sensation such as location and intensity of stimulus
|
spinothalamic tract
|
|
main relay for the spinothalamic tract
|
VPL of the thalamus is main relay; also intralaminar thalamic nuclei (central lateral nucleus) and medial thalamic nuclei (mediodorsal nuclei)
|
|
where does the spinoreticular tract terminate
|
on medullary-pontine reticular formation-projects to the intralaminar thalamic nuclei
|
|
where do the intralaminar thalamic nuclei project
|
diffusely to the entire cerebral cortex (thought to be involved in behavioral arousal)
|
|
where does the spinomesencephalic tract project
|
to midbrain periaqueductal gray matter and the superior colliculi
|
|
periaqueductal gray matter participates in
|
central modulation of pain
|
|
What spinal cord laminae do the spinothalamic and spinomesencephalic tracts mainly arise from
|
cord laminae I and V
|
|
What spinal cord laminae does the spinoreticular tract mainly arise from
|
diffusely from intermediate zone and ventral horn laminae 6-8
|
|
Brodmann areas of primary somatosensory cortex
|
3, 1, 2
|
|
somatotopic organization of primary sensory cortex
|
face lateral and leg medial
|
|
where is info from the primary somatosensory cortex conveyed
|
secondary somatosensroy association cortex within the sylvian fissure (parietal operculum)
|
|
where does further processing of somatosensory info occur
|
association cortex of posterior parietal lobe (brodman's areas 5 and 7)
|
|
when does cortical sensory loss occur
|
lesions of somatosensory cortex and adjacent regions
|
|
what does pain modulation involve
|
interactions btwn local circuits at level of spinal cord dorsal horn and long-range modulatory inputs
|
|
gate control theory
|
sensory inputs from large diameter non-pain A-Beta fibers reduce pain transmission through the dorsal horn
|
|
what does the periqueductal gray receive inputs from
|
hypothalamus, amygdala, and cortex
|
|
what does periaqueductal gray do
|
inhibits pain transmission in the dorsal horn via the rostral ventral medulla (RVM)
|
|
where is the RVM
|
pontomedullary jxn
|
|
what neurons does the RVM have
|
serotoneurgic (5-HT) neurons of the raphe nuclei
|
|
what do the serotoneurgic nerons do
|
project to the spinal cord and modulate pain in the dorsal horn
|
|
what does substance P do to the RVM
|
causes it to send inputs to the locus ceruleus-which sends noradrenergic projections to modulate pain in the spinal cord dorsal horn
|
|
divisions of the thalamus
|
medial nuclear group, lateral nuclear group, and anterior nuclear group
|
|
what divided the thalamus into these regions
|
Y-shaped white matter structure called internal medullary lamina
|
|
intralaminar nuclei
|
nuclei within the internal medullary lamina
|
|
midline thalamic cuclei
|
additional collection of nuclei adjacent to the third ventricle; several continuous with and similar to the intralaminar nuclei
|
|
thalamic reticular nucleus
|
extensive, but thin sheet enveloping the lateral aspect of the thalamus
|
|
Three main categories of thalamic nuclei
|
1) relay 2) intralaminar 3) reticular
|
|
relay nuclei
|
most of thalamus; receive inputs and project to cortex - localized and diffuse distributions
|
|
what information is relayed in the lateral geniculate nucleus (LGN)
|
visual
|
|
what information is relayed in the medial geniculate nucleus (MGN)
|
auditory
|
|
mnemonic for LGN and MGN
|
lateral light and medial music
|
|
anterior nuclear group projects to
|
limbic pathways in cortex (anterior cingulate cortex)
|
|
pulvinar
|
large, pillow-shaped nucleus that occupies most of the posterior thalamus
|
|
mediodorsal nucleus (MD)
|
major thalamic relay for frontal association cortec
|
|
intralaminar nuclei receive main inputs and outputs from
|
basal ganglia
|
|
two functional regions of intralaminar nuclei
|
caudal intralaminar nuclei and rostral intralaminar nuclei
|
|
what are caudal intralaminar nuclei involved in
|
basal ganglia circuitry
|
|
rostal intralaminar nuclei are involved in
|
basal ganglia input/output; also ascending reticular activating systems (ARAS) to the cortex
|
|
reticular nucleus location
|
thin sheet just lateral ro the rest of thalamus and just medial to internal capsule; doesn't project to cortex
|
|
what inputs does the reticular nucleus receive
|
from other thalamic nuclei and cortex and projects back to thalamus
|
|
what neurons make up most of the reticular nucleus
|
inhibitory GABAergic neurons
|
|
paresthesias
|
abnormal positive sensory phenomenon
|
|
presentation of posterior column-medial lemniscal pathways lesions
|
tingling, numb sensation, feeling of a tight band around trunk or limbs, sensation of gauze on fingers when touching objects
|
|
presentation of anterolateral pathways lesions
|
sharp, burning, or searing pain
|
|
lesions of parietal lobe
|
contralateral numb tingling, pain can be prominent
|
|
lesions of thalamus
|
severe contralateral pain (Dejerine-Roussy syndrome)
|
|
lesions of c-spine
|
Lhermitte's sign-electricity like sensation running down back into extremities upon neck flexion
|
|
lesions of nerve roots often produces
|
radicular pain that radiates down limb in a dermatomal distribution; numbness and tingling
|
|
dysesthesia
|
unpleasant, abnormal sensation
|
|
hyperpathia or allodynia
|
painful sensations provoked by minor stimuli such as light touch
|
|
lateral pons or lateral medulla lesion
|
involves anterolateral pathways and spinal trigeminal nucleus on same side; loss pain/temp contralateral body; pain/temp ipsilateral face
|
|
midial medulla lesion
|
involves medial lemniscus causing contralateral loss vibration/joint position sense
|
|
common causes of transverse spinal cord lesion
|
trauma, tumors, multiple sclerosis, transverse myelitis
|
|
hemicord lesions (Brown-Sequard syndrome)
|
ipsilateral UMN-type weakness (corticospinal), ipsilateral loss vibration and joint position sense (posterior columns), contralateral loss pain and temp (anterolateral systems)
|
|
common causes of hemicord lesions (Brown-Sequard syndrome)
|
penetrating injuries, MS, lateral compression from tumors
|
|
central cord syndrome in small lesions
|
bilateral regions of suspended sensory loss to pain and temp (spinothalmic fibers)
|
|
central cord lesion distribution in c-spine lesions
|
cape distribution
|
|
central cord syndrome in larger lesions
|
anterior horn cells damaged producing LMN deficits, UMN deficits (corticospinal), posterior columns may be involved; sacral sparing
|
|
common causes of central cord syndrome
|
spinal cord contusion, posttraumatic syringomyelia, intrinsic spinal cord tumors (hemangioblastoma), ependymoma, astrocytoma
|
|
posterior cord syndrome
|
loss of vibration and position sense below lesion
|
|
what can occur with large posterior cord syndrome lesions
|
encroachment on lateral corticospinal tracts
|
|
common causes of posterior cord syndrome
|
trauma, extrinsic compression from posteriorly located tumors, MS; vit B12 deficiency and tabes dorsalis affect posterior cord
|
|
anterior cord syndrome
|
loss of pain and temp sense (anterolateral pathways), LMN weakness (anterior horn cell damage)
|
|
what is involved with larger anterior cord syndrome lesions
|
corticospinal tracts causeing UMN signs
|
|
what symptom is common in anterior cord syndrome
|
incontinence-descending pathways controlling sphincter fxn tend to be more ventrally located
|
|
common causes of anterior cord syndrome
|
trauma, MS, anterior spinal artery infarct
|
|
sensory info from rectum, bladder, urethra, and genitalia is via sacral nerve roots
|
S2-4
|
|
where do voluntary somatic motor fibers arise that control pelvic floor muscles
|
anterior horn cells of S2-4
|
|
where do sympathetics arise for bladder intervation
|
intermediolateral cell column at T11 to L1
|
|
bilateral pathways are involved in
|
lesions that affect bowel, bladder, or sexual fxn
|
|
detrusor reflex is mediated by
|
intrinsic spinal cord circuits regulated by pontine micturition center and possibly cerebellar and basal ganglia pathways
|
|
micturition
|
initialed by voluntary relaxation of external sphincter, triggers inhibition of sympathetics to bladder neck causing relaxation, acitvation of parasympathetics causing detrusor contraction
|
|
urethral reflex
|
urethral sphincter contration triggers detrusor relaxation
|
|
lesions affecting bilateral medial frontal micturation centers result in
|
reflex activation of pontine and spinal micturition centers when bladder is full
|
|
common causes of frontal-type incontinence
|
hydrocephalus, parasagittal meningioma, bifrontal glioblastoma, traumatic brain injury, neurodegenerative disorders
|
|
lesions below pontine micturation center and above conus medullaris levels S2-4
|
initially cause flaccid, acontractile bladder--then over weeks/months into hyperreflexive bladder
|
|
common spinal cord lesions causing acontractile or hyperreflexic bladder
|
trauma, tumors, transverse myelitis, MS
|
|
Lesion of the peripheral nerves or spinal cord at S2-4
|
flaccid areflexic bladder; due to loss of parasympathetic outflow to detrusor and/or loss afferent sensory info from bladder and urethra
|
|
common causes of Lesion of the peripheral nerves or spinal cord at S2-4
|
diabetic neuropathy and compression of conus medullaris or cauda equina by trauma, tumor, disc herniation
|
|
What else can cause urinary incontinence and retention
|
prostatic hypertrophy, urethral strictures, intrinsic sphincter deficiency
|
|
what origin do desending pathways controlling fecal continence have
|
medial frontal lobes
|
|
internal smooth muscle sphincter innervation
|
sacral parasympathetics
|
|
external striated muscle sphincter innervation
|
pelvic nerves arising from Onuf's nucleus
|
|
pelvic floor muscle innervation
|
sacral anterior horn cells
|
|
what does GI motility depend on
|
parasympathetics from S2-4 for colorectal smooth muscle beyond splenic flexture; above flexture parasympathetic from vagus
|
|
what can fecal incontinence be caused by
|
diffuse cerebral or midial frontal lesions, spinal cord lesions, lesions of sacral nerve roots or pelvic or pudendal nerves
|
|
what occurs in acute spinal cord lesions
|
anal sphincter is completely flaccid; loss of parasympathetic outflow causing severe constipation
|
|
sensation from genetalia is via
|
pudendal nerve reaching to S2-4
|
|
what mediates female secretion of lubricating mucus by Bartholin's glands
|
parasympathetics
|
|
what mediates female increases in vaginal blood flow and secretions
|
sympathetics
|
|
ejaculation is mediated via
|
sympathetics - contraction of smooth muscle
|
|
what can cause sexual dysfunction
|
peripheral nerve lesions, higher-order cortical lesions, and psychological factors
|