neuro exam 3 (copy)
Terms
undefined, object
copy deck
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what is the difference between the retinal field and the visual field?
how does retinal field project onto visual cortex? -
v= left or right view from each eye
r= view on retina of opposite visual field
retinal field project to the corrosponding side of the visual cortex (RRF to RVC, LRF to LVC) - how are nasal/temporal visual fields projected onto retina and the visual cortex?
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Nasal: to lateral retinal field and ipsilateral cortex to eye ball
Temporal: to medial retinal field and contralateral cortex to eyeball - how are superior and inferior quandrants projected on retina and vis. cortex?
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superior VF projects below calcarine fissure in occipital lobe
inferior projects above it - describe the neuronal pathway of visual information
- optic fibers, retinal ganglion cells, exit eyeball, optic disk. enter cranial cavity, optic chiasm (lateral geniculate body or superior colliculus), thalamus (optic radiation fibers), visual cortex
- What is a homonymous visual deficit versus a heteronymous visual deficit? Where is the breakdown neuronally?
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homo: same VF of both eyes (rt or left). optic tract, geniculatebody, or geniculocalcarine fissure lesion
hetero: rt FV for one, left for other. Optic chasm lesion - VF defecits for lesion on optic nerve
- blindness to same eye (or to one VF, if lesion only affects part of nerve)
- VF defecits for lesion on optic tract
- homonymous hemianopsia
- VF defecits for lesion on optic chasm
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both fibers from nasal retinas: Biltemporal heteronymous hemianopsia (blind in temporal VFs)
one fiber: isilateral temporal part of retnina, nasal hemianopsia in one eye - VF defecits for lesion on optic radiation fibers
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outer geniculocalcarine: left upper quadtranopsia
dorsal geniculocalcarine: right upper quadtranopsia - VF defecits for lesion on the occipital lobe
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visual agnosia (doens't recognize visual stimuli)
prosopoagnosia (doen'st recognize faces) - What specific thalamic nuclei serve as major gateways for transmission of auditory and visual information? Where do these nuclei project in the cortex?
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aud: medial geniculat ebody (to heschls gyrus)
vis: lateral geniculate body (to occipital lobe) - where is the inferior colliculus and what is it's function?
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-auditory and visual reflexes coordinated here
-lateral lemniscus fibers ascend via pons to here
-located in the midbrain - where is the superior colliculus and what is it's function?
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-in midbrain, rostral to inferior colliculus
-mediates visual reflexes - where is the pineal gland and what is it's function?
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-located rostro-dorsal to superior colliculus
-produces melatonin - where is the cerebral aqueduct and what is it's function?
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-in lower caudal midbrain
-contains cerebrospinal fluid, and connects the third ventricle in to the fourth ventricle - where is the medial geniculate nucleus and what does it do?
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-thalamic relay center for auditory stiumli
-recieves info from ipsilateral inferior colliculus
-projects ventrally and caudally into internal capsule
-terminate in ipsi heschls gyrus - where is the lateral geniculate nucleus and what does it do?
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-receives info from retina, major visual processor
-part of the thalamus - where is the fourth ventricle and what does it do?
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-between pons and cerebellum
-provides CSF to midbrain and cerebellum - describe the path of the corticospinal tract
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precentral gyrus, corona radiata, posterior limb of internal capsule, cerebral peduncle, BS, becomes lateral corticospinal tract, ends in SC
-90% of fibers decusate at medulla (lateral CST)
-10% (anterior CST) don't - what systems compromise the pyramidal tracts?
- corticospinal and cotico bulbar
- describe the path of the coricobulbar tract
- -lower precentral gyrus, internal capsule (genu), pes pedunculi, cranial nerve nuclei, pontine nuclei (to contralateral side)
- Describe the Indirect Activation Pathway (IDAP) and tracts that make up this efferent system
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aka extrapyramidal tract
-maintains posture, muscle tone, etc
-comprised of vestibulospinal, reticulospinal, rubrospinal, and tectospinal tracts
-inhibits extensor muscle contraction, facilitates flexor activation - What is the Final Common Pathway (FCP)? What structures make up the FCP and where is it located, roughly?
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-at the SC level
-dorsal roots (sensory) and ventral roots (alpha/gamma motor) merge to yield spinla nerves - what do alpha and gamma motor neurons innervate, and where are they?
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alpha: extrafusal muscle fibers. bone to tendon. afferent impulses. muscle contractions
Gamma: control both ends of intrafusal muscle fibers. contraction of ends= passive stretch. - regarding the face, what will an upper motor neuron lesion result in?
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-affect contralateral LMN inervation to LOWER face and tongue (cranial VII and XII)
-lesion above caudal medulla decussatoin
-central facial weakness - regarding the face, what will an lower motor neuron lesion result in?
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-lesion below caudal medulla decussaion
-unilateral weakness
-"peripheral weakness" - describe spastic hemiplegia
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-acute insult (UMN lesion)
-weakness, loss of delicate skills, hypotonia
-loss of abdominal reflexes
- +babinski - describe Bell's palsy
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-LMN lesion, cranial VII
-weakness of entire face on one side
-symptoms ipsi to lesion - describe pseudobulbar palsy (aka supranuclear palsy)
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due to bilateral UMN lesions of coritcobulbar tracts
-some spasticity, movement problems
-poor smile on command
-exaggerated smile with emotional stim - describe an alternating hemiplegia
- weakness on the contralateral side of lesion above lesion and ipsilateral weakness below lesion due to lesion at point of decussaion
- describe decerebrate posture
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abnormal body posture
-rigidity, removes arm flexors with increased arm/leg extension
-toes point down
-head arch back
-caused by severe injury at BS below red nucleus but above vestibular nucleus - describe decorticate posture
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-rigid
-increased arm flexors, clenched fists, increased leg extensors
-arms bend in toward body with wrists and fingers bent & against chest
-severe brain damage involving corticospinal tract above red nucleus in midbrain region - describe LMN vs UMN innervation to the face
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LMN: ipsilateral, unilateral
UMN: BIlateral, affects both sides of upper or lower face - describe symptoms of an UMN lesion to the DAP
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-loss of skilled volluntary movement
-hyPOtonia
-hyPOrelfexia
- +babinski
-decorticate posturing - describe symptoms of an UMN lesion to the IDAP
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-poor control of posture/tone/DAP support
-hyPERtonia
-hyPERreflexia
-decerebrate posturing - what role does the cerebellum play in afferrent and efferent innervation?
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-excites both
-integrates and coodinates execution of smooth, directed movements - how do symptoms of a cerebellar lesion present?
- ataxia
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what are the basal ganglia control circuits?
what are their functions? -
-BG, Substantia nigra, subthalamus, cerebral cortex
-plan and program postural and supportive componants of motor activity and initiation of movement -
what muscles move the eye?
what nerves innervate them? -
-superior and inferior rectus, lateral and medial rectus, superior and inferior oblique muscles
-cranials III, IV and VI -
which hemisphere innervates each muscle of the eye?
what will a left hemisphere lesion of these nerves look like? -
cranial III--same side
cranial VI--opposite side
L lesion--eye looks left (cannot look right - sypmtoms of an UMN lesion
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-spastic paralysis
-increased muscle tone (hypertonia)
- +babinski
-hypereflexia - symptoms of a LMN lesion
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-weakness (flaccid)
-decreased muscle tone (hypotonia)
- -babinski
-hyporeflexia
-signs of muscle devernation (fasiculations) -
what is indicated by the absense of these visual reflexes?
-consensual reflex (pupil constricts to light)
-accomodation reflex (lens focus, pupil restricts) -
cr: problem in neuronal pathway from eye to midbrain (lateral geniculate nucleus)
ar: problem in neural network from vis. cortex back to eye (suprior colliculus) -
What is indicated by these visual problems?
-conjugate gaze (cannot move eyes to contralataral side)
-nystagmus (tremor-like eye movements)
-coma
-doll's eyes -
cg: lesion to visuomotor area (Brodman's 8)
N: BS lesion
coma: depressed BS activity
de: BS or BG lesions - what id Darrow's hypotheses on MOC function?
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1. Extend dynamic range - a gain control system
2. Control masking from background noise
3. Protect the inner ear from acoustic injury - what are Darrow's speculated function of LOC?
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1) LOC protects the cochlea from acoustic injury
2) LOC maintains bilateral symmetry of neural excitability - what is the basic function and structure of the cochlea?
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f: transmits electrical signals to the brain for sound perception
s: scala vestibuli (perilymph), scala media (endolymph), scala tympani (perilymph) - where are high and low frequency sounds perceived in the cochlea and cortex?
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high F: lower cochlea, anterolateral Heschl's gyrus
low F: higher cochlea, posteromedial Heschl's gyrus - describe the central auditory pathways including specific ganglia, nuclei, and neuronal projections.
- cochlear nuclear complex, superior olivary complex, lateral lemniscus, inferior colliculus, brachium of inferior colliculus, medial geniculate body (thalamus), geniculocortical fibers (auditory radiations), heschls gyrus
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Where is the Primary auditory cortex?
the auditory association cortex? -
pac: heschl's gyrus
aac: Wenicke's area - How is acoustic information perceived on a cortical level?
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-major inputs to PAC are from contralateral ear
-few projections from ipsilateral ear - What is meant by bilateral auditory representation, sound source localization, and tonotopic representation with respect to hearing?
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bilat: PAC receives info from BOTH ears
local: sound reaches ipsi sup. olive. nuc. first, then contra
tonotop: high Fo percieved in posteromedial heschls, low Fo in anterolateral heschls - How can you assess hearing on a central level?
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speech reception threshold
word recognition scores - What is electromotility?
- Outer Hair Cells change length in response to elctric stimuli
- What are the four processes of cochlear function?
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-Sound pressure generates Basilar Membrane motion
-Outer Hair Cells amplify motion
-Inner Hair Cells transduce motion into electricity
-Auditory Nerve transmits electrical activity to the brain - How does one test OHC function and IHC auditory nerve function?
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otoacoustic emissions
auditory brainstem response - describe IHC transduction
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-Sensory hairs vibrate, "tip-links" open ion channels into IHC
-Ions flow into IHC,
changing electrical
potential in IHC
-Electric potential causes
chemical neurotransmitter
release from IHC synapse
-Neurotransmitter diffuses
to nerve fiber and excites
electrical activity in the
form of action potentials - Describe MOC nerve cells and LOC nerve cells
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MOC: innervate outer hair cells, amplify low F sounds. ACh
LOC: innervate inner hair cells. ACh, GABA, DA, CGRP, Ucn, Opioids. Unmyelinated - Describe Type I audtory nerve fibers
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-large
-myelinated
-synapse with Inner hair cells
-make up 90-95% of auditory fibers - What is retrocochlear dysfunction?
- occurs as a result of disorders affecting the auditory nerve; for example, a tumour growing on the vestibular nerve
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describe these 3 errors of refraction:
-hypermetropia
-myopia
-astigmatism -
H; fartightedness
m: nearsightedness
as: irregular shape in cornea/lens -
describe these 3 color vision problems:
-ptotanopic
-deuteranopic
-tritanopic -
p lacks red cones
d: lacks green cones
t: lacks blue cones -
what is a visual agnosia?
prosopoagnosia?
what causes them? -
vis: doesn't recognize visual stimuli
pro: doesn't recognize faces
cause: occipital lobe lesions - What are some of the functions of thet vestibular system?
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-integrates info from semicircular canals
-regulates position of head and body
-monitros writing motor reflexes
-coodinates head and body movements
-controls eye fixation - details of cranial nerve VIII
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-made of vestibular nerve and cochlear nerve
-transmits afferent info to CNS
-involved in balance and perception of sound, integrates them - what are the 1st, 2nd, and 3rd order neurons of the auditory nerves?
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1: spiral ganglia
2: cochlear nuclei
3: thalamus - describe the dorsal acoustic stria
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-cross midline at pontomedullary junction
-terminate in contralateral lateral lemniscus - describe the intermediate acoutic stria
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-project both ipsi and contra to the superior olivary complex
-main body terminate in contralateral lateral lemniscus - describe the trapezoid body fibers
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-cross midline and terminate in contra. superior olivary nucleus
-largest and most important of 3 cochlear projections
-ipsi fibers go to either ipsi SON or ispsi Lat.Lem. - describe the superior olivary nucleus
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-recieved bilateral input from both cochlear nuclei
-sensitive to time and intensity differences
-plays part in localization - describe the Lateral Lemniscus
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-primary ascending auditory pathway
-in midbrain, extends via SON to InfColl
-fibers ascent laterally in pontine tegmentum - describe the Inferior Colliculus
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-commisural fibers here permit crossing and integration of binaural and monaural aud. info
-aids in localization
-auditory and vis. reflexes coordinated at this juncture - Describe the Medial Geniculate Body
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-thalamic relay center for auditory stimuli
-recieves info from ipsi inferior colliculus
-projects geniculocortical fibers vent. and caud. to IntCap
-terminate in ipsi Heschl's - symptoms of Vertebro-Basilar vascular insufficiency
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-vertigo (in 2/3 of cases)
-ataxic (incoordination), diplopia (double-vision)
-weakness, halucinations
-sometimes Visual Field deficits, blindness, headaches, HL, dysarthria, numbness - sypmtoms of vertebro-basilar stroke
- -ispi HL
- symptoms of AICA infarct
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-ipsi facial weakness
-ipsi protopathic loss to face
-contra protopathic loss to body
-ipsi deafness/HL - Describe the conceptualization level of the DAP
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-conscious awareness, intentional action
-cog. and affective in nature
-establish goal for action
-bilateral, widespread cortically - describe the spacial-temporal planning (linguistic planning) level of the DAP
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-interaction between symptoms
-coodination between linguistic neural networks with motor acts and temporal sequencing
-phoneme selection and ordering - describe the conceptual-programming level of motor speech planning/programming (DAP)
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-plan for neuromuscular execution organized
-intimately connected to linguistic planning - what is the function of the Indirect Activation Pathway?
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-mediates subconcious automatic muscle activities
-ex, posture and muscle tone - tracts of the IDAP
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corticorubral
corticoreticular
rubrospinal
reticulospinal
vestibulospinal - What is the function and structures of the Final Common Pathway?
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-to stimulate muscle contraction and movement
-made of cranial nerves and spinal nerves - describe the function and structures of the Basal Ganglia Control Circuits
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-plans and programs postural and supportive componants of motor activity
-made of BG, Sub. Nigra, subthalamus, cerebral cortex - describe the function and structures of the Cerebellar Control Circuits
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-integrates and coordinates execution of smooth directed movments
-made of cerebellum, cerebellar beduncles, retic. formation, red nucleus, pontine nucleus, inferior olive, and cerebral cortex - Which cranial nerves provide bilateral innervation?
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V, Trigeminal (jaw)
VII, Facial (upper face)
IX, glossopharyngeal (slallow)
X, Vagus (larynx, pharynx, VFs) - which nerves have greater UMN contralateral innervation?
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VII, facial (LOWER face)
XII, hypoglossal (tongue) - what do Muscle Spindles do?
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-identify degree and rate of change in muscle length
-maintain muscle tone
-contain intrafusal fibers
-lie parallel to extrafusal (striate) fibers - what do golgi tendon organs do?
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-monitor degree of muscle tension/contraction
-reflexively stretch to reduce muscle tension
-prevents contraction - Symptoms of UMN lesions
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-unilateral weakness to contralateral side if lesion is above pyramidal decussaion
-ipsilateral weakness if below
-Chronic: spasticity, gradual weakness
-acute: flaccidity or hypotonia, sudden weakness - symptoms of LMN disease
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-segmental loss
-musculature is flaccid, ultimately atrophies
-deep tendon reflexes are depressed
-fasiculations notes with loss of innervation