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neuro exam 3 (copy)


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copy deck
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?
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?
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?
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
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
outer geniculocalcarine: left upper quadtranopsia
dorsal geniculocalcarine: right upper quadtranopsia
VF defecits for lesion on the occipital lobe
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?
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?
-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?
-in midbrain, rostral to inferior colliculus
-mediates visual reflexes
where is the pineal gland and what is it's function?
-located rostro-dorsal to superior colliculus
-produces melatonin
where is the cerebral aqueduct and what is it's function?
-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?
-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?
-receives info from retina, major visual processor
-part of the thalamus
where is the fourth ventricle and what does it do?
-between pons and cerebellum
-provides CSF to midbrain and cerebellum
describe the path of the corticospinal tract
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
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?
-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?
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?
-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?
-lesion below caudal medulla decussaion
-unilateral weakness
-"peripheral weakness"
describe spastic hemiplegia
-acute insult (UMN lesion)
-weakness, loss of delicate skills, hypotonia
-loss of abdominal reflexes
- +babinski
describe Bell's palsy
-LMN lesion, cranial VII
-weakness of entire face on one side
-symptoms ipsi to lesion
describe pseudobulbar palsy (aka supranuclear palsy)
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
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
-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
LMN: ipsilateral, unilateral

UMN: BIlateral, affects both sides of upper or lower face
describe symptoms of an UMN lesion to the DAP
-loss of skilled volluntary movement
- +babinski
-decorticate posturing
describe symptoms of an UMN lesion to the IDAP
-poor control of posture/tone/DAP support
-decerebrate posturing
what role does the cerebellum play in afferrent and efferent innervation?
-excites both
-integrates and coodinates execution of smooth, directed movements
how do symptoms of a cerebellar lesion present?
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
-spastic paralysis
-increased muscle tone (hypertonia)
- +babinski
symptoms of a LMN lesion
-weakness (flaccid)
-decreased muscle tone (hypotonia)
- -babinski
-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)
-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?
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?
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?
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?
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
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?
-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?
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?
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?
-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?
otoacoustic emissions

auditory brainstem response
describe IHC transduction
-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
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
-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
describe these 3 errors of refraction:
H; fartightedness

m: nearsightedness

as: irregular shape in cornea/lens
describe these 3 color vision problems:
p lacks red cones

d: lacks green cones

t: lacks blue cones
what is a visual agnosia?


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?
-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
-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?
1: spiral ganglia

2: cochlear nuclei

3: thalamus
describe the dorsal acoustic stria
-cross midline at pontomedullary junction
-terminate in contralateral lateral lemniscus
describe the intermediate acoutic stria
-project both ipsi and contra to the superior olivary complex
-main body terminate in contralateral lateral lemniscus
describe the trapezoid body fibers
-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
-recieved bilateral input from both cochlear nuclei
-sensitive to time and intensity differences
-plays part in localization
describe the Lateral Lemniscus
-primary ascending auditory pathway
-in midbrain, extends via SON to InfColl
-fibers ascent laterally in pontine tegmentum
describe the Inferior Colliculus
-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
-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
-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
-ipsi facial weakness
-ipsi protopathic loss to face
-contra protopathic loss to body
-ipsi deafness/HL
Describe the conceptualization level of the DAP
-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
-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)
-plan for neuromuscular execution organized
-intimately connected to linguistic planning
what is the function of the Indirect Activation Pathway?
-mediates subconcious automatic muscle activities
-ex, posture and muscle tone
tracts of the IDAP
What is the function and structures of the Final Common Pathway?
-to stimulate muscle contraction and movement
-made of cranial nerves and spinal nerves
describe the function and structures of the Basal Ganglia Control Circuits
-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
-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?
V, Trigeminal (jaw)
VII, Facial (upper face)
IX, glossopharyngeal (slallow)
X, Vagus (larynx, pharynx, VFs)
which nerves have greater UMN contralateral innervation?
VII, facial (LOWER face)
XII, hypoglossal (tongue)
what do Muscle Spindles do?
-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?
-monitor degree of muscle tension/contraction
-reflexively stretch to reduce muscle tension
-prevents contraction
Symptoms of UMN lesions
-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
-segmental loss
-musculature is flaccid, ultimately atrophies
-deep tendon reflexes are depressed
-fasiculations notes with loss of innervation

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