Glossary of neuro exam 3
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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?
- 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
- 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
- describe spastic hemiplegia
- -acute insult (UMN lesion)
-weakness, loss of delicate skills, hypotonia
-loss of abdominal reflexes
- 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
- describe symptoms of an UMN lesion to the IDAP
- -poor control of posture/tone/DAP support
- 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)
- symptoms of a LMN lesion
- -weakness (flaccid)
-decreased muscle tone (hypotonia)
-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)
- 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,
potential in IHC
-Electric potential causes
release from IHC synapse
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
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
- 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)
-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
- 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
- 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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