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