Lecom - Neuroanatomy 07: Somatosensory Pathways

Front 1

A-α Fibers

Back 1

Diameter: 13-20 Myelinated: Yes Receptors: Muscle Spindle & Golgi Tendon Organ Sensory: Proprioception

Front 2

A-β Fibers

Back 2

Diameter: 6-12 Myelinated: Yes Receptors: Muscle Spindle = Proprioception, Meissner's Corcpuscle = Superficial touch, Merkel's Receptor = Superficial touch, Pacinian Corpuscle = Deep touch & Vibration, Ruffini Ending = Deep Touch & Vibration, Hair Receptor = Touch & Vibration

Front 3

A-δ Fibers

Back 3

Diameter: 1-5 Myelinated: Yes Receptors: Bare Nerve Ending Sensory: Pain, Temperature (Cool), Itch

Front 4

C Fibers Fibers

Back 4

Diameter: 0.2-1.5 Myelinated: Yes Receptors: Bare Nerve Ending Sensory: Temperature (Warm), Itch

Front 5

Ventral Posterior Lateral Nucleus (VPL)

Back 5

Inputs: Medial Lemniscus & Spinothalamic Outputs: Somatosensory Cortex Function: Relays Somatosensory sinput to cortex

Front 6

Ventral Posteromedial Nucleus (VPM)

Back 6

Inputs: Trigeminal Lemniscus, Trigeminothalamic tract, Taste inputs Outputs: Somatosensory and Taste Cortex Function: Relays somatosensory cranial nerve inputs and taste to cortex

Front 7

Lateral Geniculate Nucleus (LGN)

Back 7

Inputs: Retina Outputs: Primary Visual Cortex Function: Relays visual inputs to cortex

Front 8

Medial Geniculate Nucleus (MGN)

Back 8

Inputs: Inferior Colliculus Outputs: Primary Auditory Cortex Function: Relays auditory inputs to cortex

Front 9

Ventral Lateral Nucleus (VL)

Back 9

Inputs: 1 Internal Globus Pallidus, deep cerebellar nuclei, substantia nigra, pars reticulata Outputs: Motor, Premotor, Supplementary Cortex Function: Relays basal ganglia and cerebellar inputs to cortex

Front 10

Ventral Anterior Nucleus (VA)

Back 10

Inputs: 1 Outputs: 2 Function: 8

Front 11

Pulvinar

Back 11

Inputs: 1 Outputs: 2 Function: 9

Front 12

VPL (ventral posterior lateral nucleus)

Back 12

Major thalamic nuclei: Relays somatosensory spinal inputs to cortex

Front 13

VPM (ventral posteromedial nucleus)

Back 13

Major thalamic nuclei: Relays somatosensory cranial nerve inputs and taste to cortex

Front 14

Lateral geniculate nucleus (LGN)

Back 14

Major thalamic nuclei: Relays visual inputs to cortex

Front 15

Mediate geniculate nucleus (MGN)

Back 15

Major thalamic nuclei: Relays auditory inputs to cortex

Front 16

ventral lateral nucleus (VL)

Back 16

Major thalamic nuclei: Relays basal ganglia and cerebllar inputs to cortex

Front 17

Pulvinar

Back 17

Major thalamic nuclei: Behavioral orientation toward relevant visual and other stimuli

Front 18

Mediodorsal nucleus (MD)

Back 18

Major thalamic nuclei: limbic pathways, major relay to frontal cortex

Front 19

Anterior Nucleus

Back 19

Major thalamic nuclei: gets input from mammillary body-->cingulate gyrus... relays limbic pathways

Front 20

Intralaminar Nuclei

Back 20

Major thalamic nuclei: maintains alert consciousness; motor relay for basal ganglia and cerebellum

Front 21

Reticular Nucleus

Back 21

Major thalamic nuclei: regulates state of other thalamic nuclei

Front 22

Lesions of the posterior column-medial lemniscal pathways often produce these effects in patients:

Back 22

tingling, numb sensation; feeling of a tight, bandlike sensation around the trunk or limbs; or a sensation similar to gauze on the fingers when trying to palpate objects

Front 23

Lesions of the anterolateral pathways often produce these effects in patients:

Back 23

sharp, burning, or searing pain

Front 24

Lesions of the parietal lobe or primary sensory cortex may cause these effects

Back 24

contralateral numb tingling,

Front 25

lesions of the thalamus that cause severe contralateral pain

Back 25

Dejerine-Roussy syndrome

Front 26

Lhermitte's sign

Back 26

Lesions of the cervical spine: an electricity like sensation running down the back and into the extremities upon neck flexion

Front 27

lesions of the nerve roots often produce ___ pain

Back 27

radicular pain (it radiates down the limb in a dermatomal distribution and is accompanied by numbness and tingling, and is provoked by movements that stretch the nerve root)

Front 28

Dysesthesia

Back 28

unpleasant, abnormal sensation

Front 29

Allodynia

Back 29

painful sensations provoked by normally nonpainful stimuli such as light touch

Front 30

hyperpathia or hyperalgesia

Back 30

enhanced pain to normally painful stimuli

Front 31

spinal shock

Back 31

flaccid paralysis below a lesion in the spinal cord... results in loss of tendon reflexes, decreased sympathetic outflow to vascular smooth muscle causing moderately decreased BP, absent sphincteric reflexes and tone.. Over weeks-months spasticity and upper motor neuron signs develop... can be improved if treated within first 8 hours of lesion with high doses of steroids

Front 32

myelopathy

Back 32

spinal cord dysfunction

Front 33

infarction of the spinal cord is usually caused by

Back 33

an anterior spinal artery occlusion-->this leads to anterior cord syndrome

Front 34

infectious or inflammatory in etiology. Pts present with spinal cord dysfunction that develops quickly (hours)

Back 34

myelitis -CSF will have increased WBC count (lymphocytic) and an MRI will reveal T2 bright areas

Front 35

Stereognosis

Back 35

the ability to perceive and recognize the form of an object using cues from texture, size, spatial properties, and temperature

Front 36

stereognosis is mediated by the ____ pathway of the CNS

Back 36

posterior column/medial lemniscal pathway

Front 37

Graphesthesia

Back 37

ability to recognize writing on the skin purely by the sensation of touch

Front 38

What does loss of graphesthesia indicate

Back 38

Loss of graphesthesia indicates either parietal lobe damage on the side opposite the hand tested or damage to the dorsal columns pathway at any point between the tested point and the contralateral parietal lobe.

Front 39

Hemianopia

Back 39

decreased vision or blindness which takes place in half the visual field of one or both eyes

Front 40

involving the internal capsule, lateral geniculate, or optic radiations

Back 40

hemianopia can be caused by lesions.. (where)

Front 41

sensory level

Back 41

diminished sensation in all dermatomes below the level of the lesion

Front 42

transverse cord lesions

Back 42

sensory level is often found in _____ lesions

Front 43

Hemicord Lesions: Brown Sequard Syndrome-- Damage to the lateral corticospinal tract causes _____ upper motor neuron type weakness

Back 43

Damage to the lateral corticospinal tract causes *ipsilateral* upper motor neuron type weakness

Front 44

Hemicord Lesions: Brown Sequard Syndrome-- damage to the posterior columns causes ______ loss of vibration and joint position sense

Back 44

damage to the posterior columns causes *ipsilateral* loss of vibration and joint position sense

Front 45

Hemicord Lesions: Brown Sequard Syndrome-- interruption of the anterolateral system will cause _____ loss of pain and temperature sensation

Back 45

interruption of the anterolateral system will cause *contralateral* loss of pain and temperature sensation

Front 46

common causes of Brown-Sequard syndrome

Back 46

penetrating injuries, multiple sclerosis, lateral compression from tumors

Front 47

_____ lesions in the _____ cord produces a cape distribution

Back 47

*Central cord* lesions in the *cervical* cord produce a cape distribution

Front 48

common causes of central cord syndrome

Back 48

spinal cord contusion, nontraumatic or posttraumatic syringomelia, intrinsic spinal cord tumors (hemangioblastoma, ependymoma, astrocytoma)

Front 49

small lesion: damage to the spinothalamic fibers crossing the ventral comissure cause bilateral regions of suspended sensory loss to pain and temp ->what syndrome?

Back 49

central cord syndrome

Front 50

larger lesions of central cord syndrome also affect...

Back 50

the anterior horn cells.. therefore it will produce lower motor neuron deficits at the level of the lesions... may also have sacral sparing

Front 51

Lesions of the posterior columns cause loss of vibratin and position sense below the level of the lesion

Back 51

posterior cord syndrome

Front 52

what two diseases preferentially affect the posterior cord

Back 52

Vitamin B12 deficiency and tabes dorsalis (tertiary syphillis)

Front 53

damage to the anterolateral pathways causes loss of pain and temperature sensation below the level of the lesions, and damage to the anterior horn cells produoces lower motor neuron weakness a the level of the lesion

Back 53

anterior cord syndrome***incontinence is common because the descending pathways controlling sphincter function tend to be more ventrally located

Front 54

causes of anterior cord syndrome

Back 54

trauma, MS, anterior spinal artery infarct

Front 55

What nerves are sensory information from the rectum, bladder, urethra, and genitalia conveyed to the spinal cord by

Back 55

S2-4

Front 56

somatic innervation of urethra sphincter: what nerve roots and what nuclei for motor pathway

Back 56

S3*, S4; onuf's nucleus

Front 57

somatic innervation of external anal sphincter: what nerve roots and what nuclei for motor pathway

Back 57

S3, S4*; onuf's nucleus

Front 58

Where do pelvic parasympathetics arise from

Back 58

sacral parasympathetic nuclei at S2-S4

Front 59

Where do pelvic sympathetics arise from

Back 59

intermediolateral cell column at T11-L1

Front 60

An infarct of the left postcentral gyrus arm area and adjacent parietal cortex would be caused by occlusion of *a cortical branch of the left middle cerebral artery

Back 60

An infarct of the left postcentral gyrus arm area and adjacent parietal cortex would be caused by occlusion of ___

Front 61

dysmetria

Back 61

refers to a lack of coordination of movement typified by the undershoot or overshoot of intended position with the hand, arm, leg, or eye

Front 62

with clinical localization of a lesion, what level are arms involved

Back 62

C5

Front 63

innervation of finger extensors and muscles for grip

Back 63

C8-T1

Front 64

triceps innervation

Back 64

C7

Front 65

urinary retnetion caused by flaccid bladder with preserved hyperactive urinary sphincter reflexes can be caused by...

Back 65

lesions below the pontine micturition center and above the conus medullaris

Front 66

fecal incontinence with absent rectal tone can be seen in _____ lesions

Back 66

cauda equina or acute spinal cord lesions

Front 67

Hypesthesia

Back 67

diminished sensitivity

Front 68

when tactile stimulie appear to be grossly exaggerated

Back 68

hyperesthesia

Front 69

What mechanoreceptor detects vibration

Back 69

pacinian corpuscles

Front 70

What mechanoreceptor mediates superficial phasic touch sensation

Back 70

Meissner's corpuscles

Front 71

What mechanoreceptor relays information about static limb position

Back 71

muscle spindle afferents

Front 72

A lesion of the dorsal column usually abolishes ____ tactile discrimination

Back 72

ipsilateral

Front 73

A lesion of the spinothalamic tract, pain perception is lost on the ____ side of the body

Back 73

contralateral

Front 74

complete loss of proprioceptive sensation from a spinal lesions requires..

Back 74

bilateral interruption of the dorolateral pathway (both dorsal columns and the lateral cervical system in the dorsal part of the lateral columns)

Front 75

the loss of ability to recognize common objects such as keys, coins, by touching and handling them with the eyes closed

Back 75

astereognosis (could be a sign of injury to the lemniscal pathway)

Front 76

Romberg sign

Back 76

patient stands with feet closed together. Sway is observed. Patient then closes eyes and sway is observed. If there is an increase in sway with the eyes closed, the sign is +. (can be a sign of a dorsolateral lesion)

Front 77

Lesions of the thalamus can cause severe contralateral pain called what?

Back 77

Dejerine-Roussy syndrome

Front 78

What sign often accompanies lesions of the cervical spine?

Back 78

Lhermitte's sign --an electric like sensation running down the back and into the extremities upon neck flexion

Front 79

hyperalgesia or hyperpathia

Back 79

enhanced pain to normally painful stimuli

Front 80

What are 3 of the most common causes of spinal cord dysfunction?

Back 80

Extrinsic compression due to: 1.) degenerative disease of the spine 2.) trauma 3.) metastatic cancer

Front 81

What phase characterizes acute severe lesions of the spinal cord?

Back 81

spinal shock --characterized by flaccid paralysis below the lesion, loss of tendon reflexes, decreased sympathetic outflow to vascular smooth muscle causing moderately decreased BP and absent sphinteric reflexes and tone

Front 82

Spread of a metastasis to the _______ is by far the most common cause of neoplastic spinal cord compression.

Back 82

epidural space

Front 83

What vessel usually occluded in spinal cord infarction?

Back 83

anterior spinal artery occlusion

Front 84

Neurons in the posterior column/medial lemniscal system carry what type of sensation?

Back 84

vibration and position sense

Front 85

The anterolateral or trigeminothalamic systems carry what sensation in the spinal cord?

Back 85

pain and temperature sensation

Front 86

Deficit is contralateral to the lesion. Discriminative touch and joint position sense are often most severely affected. What is the lesion?

Back 86

primary somatosensorycortex

Front 87

Deficit is contralateral to the lesion. Deficit may be more noticeable in the face, hand (particularly in the lips and fingertips), and foot. All sensory modalities may be involved, sometimes w/ no motor deficit. What type of lesion?

Back 87

Lesion to thalamic ventral posterior lateral (VPL) and ventral posterior medial (VMP) nuclei or thalamic somatosensory radiations.

Front 88

What type of lesion causes loss of pain and temp sensation in the body opposite the lesion, and loss of pain and temp sensation in the face on the same side as the lesion? The lesion involves anterolateral pathways and the spinal trigeminal nucleus on the same side

Back 88

Lateral pons or lateral medulla

Front 89

Lesion involves the medial lemniscus, causing contralateral loss of vibration and joint position sense. What lesion?

Back 89

medial medulla

Front 90

All sensory and motor pathways are either partially or completely interrupted. Diminished sensation present in all dermatomes below the level of the lesion. What lesion?

Back 90

transverse cord lesion

Front 91

Lesion of the posterior columns causes loss of vibration and position sense below the level of the lesion. What type of lesion?

Back 91

posterior cord syndrome

Front 92

Damage to the anterolateral pathways causes loss of pain and temp sensation below the level of the lesion, and damage to the anterior horn cells produces lower motor neuron weakness at the level of the lesion. What type of lesion?

Back 92

Anterior cord syndrome

Front 93

What nucleus controls the urethral and anal sphincters?

Back 93

sphincteromotor nucleus of Onuf or just Onuf's nucleus

Front 94

Sympathetics for bladder function, erection and ejaculatory function come from what vertebral level?

Back 94

T11, T12, L1 from the intermediolateral column

Front 95

Sacral parasympathetic nuclei arise from what vertebral level?

Back 95

S2-S4

Front 96

What brain center activates the detrusor (voiding) reflex?

Back 96

pontine micturition center

Front 97

Micturition is initiated by what brain center?

Back 97

medial frontal micturition center that activates the voiding, or detrusor, reflex

Front 98

How does the detrusor reflex work?

Back 98

1.) Have voluntary relaxation of the external urethral sphincter 2.) Get inhibition of sympathetics to the bladder neck causing it to relax 3.) Activation of PNS, causing the detrusor muscle to contract

Front 99

What are Sx of a lesion affecting bilateral medial frontal micturition centers (activate voiding)?

Back 99

Have reflex activation of pontine and spinal micturition when the bladder is full --Urine flow and bladder emptying is normal --Loss of voluntary control --Individual may or may not be aware of incontinence

Front 100

What are Sx of a lesion below the pontine micturition center and above the conus medullaris levels S2-S4?

Back 100

Initially have a flaccid, acontractile (atonic) bladder --Then get hyperreflexic (spastic) bladder --Results in urinary retention and bladder distention --Catheter required

Front 101

What condition often occurs in a hyperreflexic bladder?

Back 101

detrusor-sphincter dyssynergia --in which both detrusor and urethral sphincter tone are increased in an uncoordinated/antagonistic fashion --Have urinary frequency and incontinence

Front 102

What deficit caused by lesions of the peripheral nerves or of the spinal cord at S2-S4?

Back 102

flaccid areflexic bladder, --causes overflow incontinence

Front 103

How would an acute spinal cord lesion affect bowel function?

Back 103

anal sphincter is completely flaccid, --loss of sacral parasympathetic outflow, causes severe constipation

Front 104

Sensation from the genitalia is conveyed by what nerve?

Back 104

pudendal nerve (S2-S4)

Front 105

What part of the ANS causes ejaculation?

Back 105

sympathetic mediated contraction of smooth muscle (seminal vesicles, vas deferens, prostate, bladder neck) --causes emission of semen into the urethra

Front 106

what does somatosensory refer to

Back 106

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

Front 107

What does the posterior column-medial lemniscal pathway convey

Back 107

proprioception, vibration sense, and fine discriminative touch

Front 108

What does the anterolateral pathway convey

Back 108

pain, tmperature sense, and crude touch

Front 109

conduction velocity of small vs large and mylinated vs unmylinated

Back 109

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

Front 110

where are sensory neuron cell bodies

Back 110

dorsal root ganglia

Front 111

type of axons of neurons in dorsal root ganglia

Back 111

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 112

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

Back 112

dermatome

Front 113

somatotopic organization of posterior column

Back 113

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

Front 114

where do many of the posterior column axons ascend to

Back 114

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

Front 115

gracile fasciculus

Back 115

medial portion that carries info from legs and lower trunk

Front 116

cuneate fasciculus

Back 116

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

Front 117

where do first order neurons in gracile and cuneate fasciculi synapse

Back 117

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

Front 118

where do axons of second order neurons decussate (cross)

Back 118

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

Front 119

orientation of medial lemniscus

Back 119

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

Front 120

where do secondary neurons of posterior column synapse

Back 120

ventral posterior lateral nucleus (VPL) of the thalamus

Front 121

Where do axons from VPL go

Back 121

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

Front 122

What pathway conveys touch sensation for the face

Back 122

trigeminal lemniscus

Front 123

pathway of trigeminal lemniscus

Back 123

ventral posterior medial nucleus (VPM) to somatosensory cortex

Front 124

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

Back 124

cortical layer IV mostly and deeper portions of layer III

Front 125

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

Back 125

synapse immediately in gray matter of spinal cord

Front 126

where in the spinal cord do these axons synapse

Back 126

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

Front 127

Lissauer's tract

Back 127

tract where fibers ascend or descend before entering gray matter

Front 128

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

Back 128

spinal cord anterior (ventral) commissure)

Front 129

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

Back 129

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

Front 130

lateral cord lesion will affect contralateral pain and temperature beginning where

Back 130

a few segments below the level of lesion

Front 131

somatotopic organization of anterolateral pathways

Back 131

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

Front 132

where are anterolateral pathways located when they reach the medulla

Back 132

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

Front 133

where do axons of anterolateral pathways go after medulla

Back 133

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

Front 134

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

Back 134

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

Front 135

whar carries pain and temp sensation for the face

Back 135

trigeminothalamic tract; similar to anterolateral pathway

Front 136

three tracts in the anterolateral pathway

Back 136

spinothalamic, spinoreticular, and spinomesencephalic tracts

Front 137

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

Back 137

spinothalamic tract

Front 138

main relay for the spinothalamic tract

Back 138

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

Front 139

where does the spinoreticular tract terminate

Back 139

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

Front 140

where do the intralaminar thalamic nuclei project

Back 140

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

Front 141

where does the spinomesencephalic tract project

Back 141

to midbrain periaqueductal gray matter and the superior colliculi

Front 142

periaqueductal gray matter participates in

Back 142

central modulation of pain

Front 143

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

Back 143

cord laminae I and V

Front 144

What spinal cord laminae does the spinoreticular tract mainly arise from

Back 144

diffusely from intermediate zone and ventral horn laminae 6-8

Front 145

Brodmann areas of primary somatosensory cortex

Back 145

3/1/2002

Front 146

somatotopic organization of primary sensory cortex

Back 146

face lateral and leg medial

Front 147

where is info from the primary somatosensory cortex conveyed

Back 147

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

Front 148

where does further processing of somatosensory info occur

Back 148

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

Front 149

when does cortical sensory loss occur

Back 149

lesions of somatosensory cortex and adjacent regions

Front 150

what does pain modulation involve

Back 150

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

Front 151

gate control theory

Back 151

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

Front 152

what does the periqueductal gray receive inputs from

Back 152

hypothalamus, amygdala, and cortex

Front 153

what does periaqueductal gray do

Back 153

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

Front 154

where is the RVM

Back 154

pontomedullary jxn

Front 155

what neurons does the RVM have

Back 155

serotoneurgic (5-HT) neurons of the raphe nuclei

Front 156

what do the serotoneurgic nerons do

Back 156

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

Front 157

what does substance P do to the RVM

Back 157

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

Front 158

divisions of the thalamus

Back 158

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

Front 159

what divided the thalamus into these regions

Back 159

Y-shaped white matter structure called internal medullary lamina

Front 160

intralaminar nuclei

Back 160

nuclei within the internal medullary lamina

Front 161

midline thalamic cuclei

Back 161

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

Front 162

thalamic reticular nucleus

Back 162

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

Front 163

Three main categories of thalamic nuclei

Back 163

1) relay 2) intralaminar 3) reticular

Front 164

relay nuclei

Back 164

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

Front 165

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

Back 165

visual

Front 166

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

Back 166

auditory

Front 167

mnemonic for LGN and MGN

Back 167

lateral light and medial music

Front 168

anterior nuclear group projects to

Back 168

limbic pathways in cortex (anterior cingulate cortex)

Front 169

pulvinar

Back 169

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

Front 170

mediodorsal nucleus (MD)

Back 170

major thalamic relay for frontal association cortec

Front 171

intralaminar nuclei receive main inputs and outputs from

Back 171

basal ganglia

Front 172

two functional regions of intralaminar nuclei

Back 172

caudal intralaminar nuclei and rostral intralaminar nuclei

Front 173

what are caudal intralaminar nuclei involved in

Back 173

basal ganglia circuitry

Front 174

rostal intralaminar nuclei are involved in

Back 174

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

Front 175

reticular nucleus location

Back 175

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

Front 176

what inputs does the reticular nucleus receive

Back 176

from other thalamic nuclei and cortex and projects back to thalamus

Front 177

what neurons make up most of the reticular nucleus

Back 177

inhibitory GABAergic neurons

Front 178

paresthesias

Back 178

abnormal positive sensory phenomenon

Front 179

presentation of posterior column-medial lemniscal pathways lesions

Back 179

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

Front 180

presentation of anterolateral pathways lesions

Back 180

sharp, burning, or searing pain

Front 181

lesions of parietal lobe

Back 181

contralateral numb tingling, pain can be prominent

Front 182

lesions of thalamus

Back 182

severe contralateral pain (Dejerine-Roussy syndrome)

Front 183

lesions of c-spine

Back 183

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

Front 184

lesions of nerve roots often produces

Back 184

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

Front 185

hyperpathia or allodynia

Back 185

painful sensations provoked by minor stimuli such as light touch

Front 186

lateral pons or lateral medulla lesion

Back 186

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

Front 187

midial medulla lesion

Back 187

involves medial lemniscus causing contralateral loss vibration/joint position sense

Front 188

common causes of transverse spinal cord lesion

Back 188

trauma, tumors, multiple sclerosis, transverse myelitis

Front 189

hemicord lesions (Brown-Sequard syndrome)

Back 189

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

Front 190

common causes of hemicord lesions (Brown-Sequard syndrome)

Back 190

penetrating injuries, MS, lateral compression from tumors

Front 191

central cord syndrome in small lesions

Back 191

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

Front 192

central cord lesion distribution in c-spine lesions

Back 192

cape distribution

Front 193

central cord syndrome in larger lesions

Back 193

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

Front 194

common causes of central cord syndrome

Back 194

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

Front 195

posterior cord syndrome

Back 195

loss of vibration and position sense below lesion

Front 196

what can occur with large posterior cord syndrome lesions

Back 196

encroachment on lateral corticospinal tracts

Front 197

common causes of posterior cord syndrome

Back 197

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

Front 198

anterior cord syndrome

Back 198

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

Front 199

what is involved with larger anterior cord syndrome lesions

Back 199

corticospinal tracts causeing UMN signs

Front 200

what symptom is common in anterior cord syndrome

Back 200

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

Front 201

common causes of anterior cord syndrome

Back 201

trauma, MS, anterior spinal artery infarct

Front 202

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

Back 202

S2-4

Front 203

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

Back 203

anterior horn cells of S2-4

Front 204

where do sympathetics arise for bladder intervation

Back 204

intermediolateral cell column at T11 to L1

Front 205

bilateral pathways are involved in

Back 205

lesions that affect bowel, bladder, or sexual fxn

Front 206

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

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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

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urethral reflex

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urethral sphincter contration triggers detrusor relaxation

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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

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common causes of frontal-type incontinence

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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

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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

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trauma, tumors, transverse myelitis, MS

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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

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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

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What else can cause urinary incontinence and retention

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prostatic hypertrophy, urethral strictures, intrinsic sphincter deficiency

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what origin do desending pathways controlling fecal continence have

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medial frontal lobes

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internal smooth muscle sphincter innervation

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sacral parasympathetics

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external striated muscle sphincter innervation

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pelvic nerves arising from Onuf's nucleus

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pelvic floor muscle innervation

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sacral anterior horn cells

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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

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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

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what occurs in acute spinal cord lesions

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

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sensation from genetalia is via

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pudendal nerve reaching to S2-4

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

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parasympathetics

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what mediates female increases in vaginal blood flow and secretions

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sympathetics

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ejaculation is mediated via

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sympathetics - contraction of smooth muscle

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what can cause sexual dysfunction

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