Ear & Eye, Exam #2

Front 1

what are the fluids contained in the internal ear? what are their compositions?

Back 1

the bony labyrinth: PERIlymph (low K+, high Na+). typical.

the osseus labyrinth: ENDOlymph (high K+, low Na+). unique.

Front 2

how many bony canals make up the cochlea? what is it spiralled AROUND?

Back 2

the cochlea is a single bony canal, wound 2 1/2 times around the modiolus (central bony core) with a limbus projecting from it.

Front 3

how many spaces are within the cochlea? how are they divided?

Back 3

BTWN membranes: cochlear duct, aka scala media

it's roof: vestibular (Reissner's) membrane.

it's floor: basilar membrane (attached centrally to the limbus).

scala vestibuli: btwn vestibular mem. & bony wall

scala tympani: btwn basilar mem. & bony wall

s.vestibuli and tympani are connected at the APEX of the cochlea.

Front 4

both hearing and balance are based on hair cells bathed in ____?

Back 4

ENDOLYMPH!

Front 5

what is the organ of corti? which hair cells contact the tectorial membrane?

Back 5

the organ of corti is a spiral strip of specialized mechanoRECEPTOR hair cells and SUPPORTING cells resting on the basilar membrane at its central side, and covered by the tectorial membrane.

OUTER hair cells contact the tectorial membrane.

Front 6

what is the position of the auditory hair cells? how is sound transduced from the outer ear to the basilar membrane?

Back 6

auditory hair cells are btwn the basilar membrane at their base and the tectorial membrane at the tips of the stereocilia.

pressure waves in PERIlymh originate from the footplate of the stapes at the oval window of the vestibule.

those pressure waves cause the basilar membrane to move up and down.

Front 7

what type of force is created when the basilar membrane vibrates? where?

Back 7

SHEAR forces are generated between the tectorial membrane and the stereocilia when the basilar membrane vibrates.

Front 8

why are the auditory hair cells considered mechanoreceptors?

Back 8

basilar membrane UP:
stereocilia bent AWAY from limbus = DEPOLARIZATION

basilar membrane DOWN:
stereocilia bent TOWARDS limbus = HYPERPOLARIZATION

Front 9

how do loud sounds damage hearing?

Back 9

loud sounds cause extreme vibration which may shear the hairs off the hair cells (or otherwise damage the o of c) producing hearing loss OF THOSE FREQUENCIES.

Front 10

what is the spiral ganglion? how is it involved in sound transduction?

Back 10

the spiral ganglion is a grouping of the bipolar cell bodies of the peripheral processes of the organ of corti.

a depolarized hair cell transmits impulse to peripheral process(dendrite) of spiral ganglion. *excitatory*

Front 11

the vast majority of peripheral processes innervate ______ and almost all auditory info passing centrally comes from these.

Back 11

INNER hair cells!

Front 12

what is tonotopy? how is it distributed?

Back 12

tonotopy = pitch localization (aka orderly relationship btwn frequency and location)

HIGH pitch (short wave): proximal (basilar base)

LOW pitch (longer wave):
distally (basilar apex)

Front 13

what is the afferent nerve distribution with respect to inner and outer hair cells?

Back 13

ONE inner hair cell produces MANY afferent nerve fibers.

MANY outer hair cells produce ONE afferent nerve fiber.

Front 14

where is the cochlear spiral ganglion located?

Back 14

within the modiolus.

Front 15

how is the cochlear nerve formed? describe it's path as the vestibulocochlear nerve

Back 15

central processes of the spiral ganglion cells project through channels in the modiolus to converge at the distal end of the internal acoustic meatus (IAM): cochlear nerve!

c + v = VIII (shares IAM with CN VII and labyrinthine artery of AICA)

VIII crosses subarachnoid space to brainstem where it enters at the cerebellopontine angle.

VIII bifurcates to dorsal and ventral cochlear nuclei.

Front 16

where do the primary cochlear afferents synapse? where are the locations?

Back 16

auditory axons in the 8th cranial nerve synapse on the ipsilateral cochlear nuclei!

dorsal and ventral cochlear nuclei are located superficially in the ROSTRAL medulla lateral to the base of the INFERIOR cerebellar peduncle.

Front 17

what are the auditory nuclei? how many cochlear nuclei are there?

Back 17

the auditory nuclei:
cochlear
relay (ascending order):
superior olivary
lateral lemniscus
inferior colliculus
medial geniculate

there are THREE cochlear nuclei:
dorsal
anteroventral
posteroventral

Front 18

what are possible causes of unilateral deafness?

Back 18

unilateral lesion of any of the structures from o of c thru cochlear nuclei:

shearing of stereocilia (high amp sound)

neuroma of IAM

occlusion of AICA

Front 19

what are the pathways of the afferent auditory fibers after synapsing on the cochlear nuclei?

Back 19

dorsal: decussate & ascend to inferior colliculus

ventral: project bilaterally to superior olivary in caudal pons (TRAPEZOID of ventral tegmentum in caudal pons, btwn and ventral to ML)

Front 20

what forms the lateral lemniscus (LL)?

Back 20

lateral lemniscus is formed from ASCENDING fibers from superior olivary and dorsal cochlear nuclei.

LL ascends thru the pons to caudal midbrain, synapse on inferior colliculus.

PONS: LL is lateral to ALS which is lateral to ML. nuerons along the way = nucleus of LL.
lemniscal fibers MAY synapse here.
projection fibers from LLnucleus may decussate to CL LLnucleus.

Front 21

what types of fibers does the lateral lemniscus carry?

Back 21

2nd order and HIGHER axons

Front 22

what is the major auditory relay nucleus in the caudal midbrain tectum? what synapses here?

Back 22

inferior colliculus is the major relay center in the caudal midbrain tectum.

most lateral lemniscus fibers synapse here, including:

1.IL & CL s. olivary axons
2.direct (unsynapsed) fibers from CL dorsal cochlear nuclei
3.IL and CL LLnuclei axons

Front 23

what is the path of neurons after synapsing on the inferior colliculus?

Back 23

they project bilaterally, decussation occurs thru the commisure of the inferior colliculi.

fibers project thru the brachium of the inferior colliculus to the medial geniculate nucleus.

Front 24

what is the medial geniculate nucleus? what is the pathway of it's neurons?

Back 24

m.geniculate nucleus is a thalamic SENSORY relay nucleus on the ventral thalamus.

fibers project thru the sublenticular (lower)part of the posterior IC to form the AUDITORY RADIATION (AR)in the temporal lobe.

AR ends on superior surface of temporal lobe (primary auditory cortex).

Front 25

which auditory pathway is bilateral (binaural) and polysynaptic? what does this mean clinically?

Back 25

the central ascending auditory pathway is bilateral, it can extract features of sound and compute it's source.

a uni lesion to the tracts/relay nuclei SUPERIOR to the cochlear nuclei DOES NOT produce uni deafness b/c supply is bilateral. (there WILL be deficits though.)

Front 26

which nuclei projects to Heschl's gyri? what BA is located there?

Back 26

medial geniculate nucleus projects IL to transverse temporal gyri (heschl's).

this is BA 41(42), in the floor of the lateral sulcus.

Front 27

what is the tonotopy of the primary auditory cortex?

Back 27

HIGH f: posteromedial
LOW f: anterolateral

Front 28

what allows the CNS to modify it's input? how is sensitivity regulated?

Back 28

descending (centrifugal) pathways allow the CNS to have "selective hearing".

olivocochlear fibers regulate sensitivity. (olivocochlear bundle is part of VIII)

Front 29

a lesion of ____ produces loss of speech recognition.

explain this area's location.

Back 29

WERNICKE'S area (via MCA)

wernicke's is the posterior part of BA22, which surrounds the primary auditory cortex (41) along with BA42. lateral surface of superior temporal gyrus.

Front 30

what gyri are involved with speech recognition?

Back 30

wernicke's area
supramarginal
angular

Front 31

how can the secondary auditory association cortexes be differentiated?

Back 31

LEFT: larger
RIGHT: emotional aspects of speech (tone)

Front 32

which pathway is involved with "what" is making the sound? "where"?

Back 32

what: frontal lobe
where: parietal lobe

Front 33

what structure interconnects the auditory cortices?

Back 33

the corpus callosum.

Front 34

an acoustic neuromma may cause ipsilateral deafness. where do they often occur? what other symptoms are present?

Back 34

acoustic neurommas often occur along the VIII nerve from the CP angle to the IAM.

symptoms may also include facial paralysis.

Front 35

what is the arterial supply to the pontine lateral lemniscus? inferior colliculus? medial geniculate nucleus? primary and secondary auditory cortices?

Back 35

LLnucleus: bbrs of the basilar artery.

inferior colliculus: superior cerebellar artery

medial geniculate nucleus: posterior cerebral artery.

auditory cortices: MCA

Front 36

where is the inner ear located? what is the vestibular system?

Back 36

inner ear is located in the petrous part of the temporal bone btwn middle ear (tympanic cavity) laterally and IAM medially.

vestibular system:

receptors of semicircular canals and vestibular canals acting in concert.

Front 37

what do the receptors of the vestibular system detect? how do the receptors differ?

Back 37

receptors detect head motion (acceleration) and head position (relative to gravity).

utricle and saccule fxn via inertia and gravity. STATIC.

SCCs fxn via fluid movement. DYNAMIC.

Front 38

what is a macula? where is it located?

Back 38

a macula is a receptor organ located within the utricle and saccule, found in the bony labyrinth.

it is a field of hair cells whose apical surfaces have an array of stereocilia and ONE kinocilium

Front 39

how are the hair cells in the bony labyrinth and the membranous labyrinth different?

Back 39

both the membranous and bony hair cells have stereocilia and one kinocilium, but the bony cilia are embedded in otolithic membrane, crystallized for stability.

the cilia of the membranous labyrinth projects into gelatinous cupula, no stones.

Front 40

why does the otolithic membrane have calcium carbonate?

Back 40

b/c the utricle and saccule operate via static movement. the added weight increases the inertial and gravitational mass.

Front 41

how is cellular bending utilized in the vestibular system?

Back 41

STATIC:
stereo TOWARDS kino: DEPOLARIZATION

stereo AWAY from kino: HYPERPOLARIZATION

**dynamic is SAME plus:
endolymph towards utricle = depolarization

endolymph away from utricle = hyperpolarization

Front 42

how is the brain constantly provided with information about head position?

Back 42

macular orientation:

utricular are horizontal, saccular are sagittal. the hair cell fields are divided in half and utricular cells point towards e/o, saccular away from e/o.

Front 43

what is scarpa's ganglion?

Back 43

peripheral processes of bipolar neurons from each ampullae, utricle and saccule converging at the lateral IAM.

Front 44

where do vestibular and cochlear fibers diverge to different nuclei? what types of fibers are they?

Back 44

v and c diverge at the brainstem. the are both SSA fibers.

Front 45

where are the vestibular nuclei located? how many components are there to this nucleus?

Back 45

they are located laterally, next to the inferior cerebellar peduncle in the dorsolateral tegmentum of rostral (open) medulla.

FOUR components: superior, inferior, medial and lateral vestibular nuclei.

Front 46

what are the two pathways of the vestibular primary afferents?

Back 46

1.synapse in vestibular nuclei, then to flocculonodular cortex and BACK to vestibular nuclei.

2.synapse in flocculonodular lobe of cerebellum (vestibulocerebellar path).

cerebellum is used to fine-tune motor reflex output! ICP is utilized for the parallel circuit.

Front 47

what is vestibular information used to accomplish? what tracts are used for these tasks?

Back 47

vestibular information:
1.maintain stable image on retina during head movements
2.maintain balance/posture

rostrally: MLF bilaterally
caudally: vestibulospinal IL

Front 48

why do vestibular nuclei project thru the MLF?

Back 48

vestibular nuclei project bilaterally to the MLF to access to nuclei of IV, VI and III to coordinate EYE movmement with HEAD position.

Front 49

what are the various pathways of the vestibular nuclei caudally?

Back 49

MEDIAL vestibulospinal tract:

BI-laterally in anterior funiculus (may be considered a MLF component) in CERVICAL and UPPER THORACIC LEVELS.

LATERAL vestibulospinal:

IL in ventral lateral funiculus at ALL LEVELS OF SPINAL CORD.

Front 50

what does loss of macular fxn cause? where might this occur?

Back 50

loss of macular fxn may cause the pt to fall to SIDE OF LESION b/c of EXTENSOR loss.

vestibulospinal neurons synapse on interneurons in the ventral horn; they inhibit proximal flexor mm grps and excite proximal extensor grps.

Front 51

how do vestibular fibers prevent vertigo?

Back 51

the utricular maculae projects fibers to the MLF which synapse with III, IV and VI nuclei to cause rolling of the eyes OPPOSITE to direction of head tilt.
(eye mm nuclei all located in dorsal medial tegmentum)

NS attempts to maintain a stable visual image on the retina.

Front 52

describe the position of the 3 semicircular canals (SCC).

Back 52

horizontal (lateral): bulges LATERALLY into medial wall of middle ear cavity.

anterior & posterior: ABOVE horizontal, they all meet at 90 degree angle.

**anterior of one side is in the same plane of the posterior on the opposite side**

SCC's representing same plane fxn as COMPLIMENTARY PAIRS.

Front 53

name the important aspects of the SCC's and their fxns.

Back 53

each SCC has an enlargement near it's utricle: ampulla with receptor organ, crista ampullaris.

Front 54

where does the crista ampullaris project? what does it contain?

Back 54

the crista ampullaris projects into the lumen of the SSC. it has stereocilia and one kinocilium which project into the cupula.

Front 55

how is sound transduced in the SCCs?

Back 55

currents in the endolymph bend the cupula which bends the hair cells.

hair cells are all oriented same direction:
endolymph towards utricle (utriculopetal), stereo towards kino = DEPOL.

endolymph away from utricle (utriculofugal), stereo away from kino = HYPER

Front 56

what occurs when the head turns left, with regards to the SCCs?

Back 56

left bony canal moves P, so fluid moves A = hair cells bent TOWARD utricle.
DEPOLARIZATION ON SIDE OF TURN

right bony canal moves A, fluid P = hair cells AWAY from utricle.
HYPERPOLARIZATION ON SIDE OPPOSITE FROM TURN.

Front 57

how are the eye mm involved with horizontal head motion?

Back 57

VI and III are involved:

LEFT turn:
R lr and L mr contract.
R mr and L lr relax.
EYES NEED TO TURN RIGHT.

accomplished via bilateral projections of vestibular nuclei.

Front 58

what is optokinetic nystagmus? how is nystagmus defined?

Back 58

optokinetic nystagmus is the fast and slow alternating movement brought about by spinning the head.

nystagmus is defined by FAST phase direction.

*abnormal nystagmus = peripheral or brainstem dz*

Front 59

what positioning needs to be considered when doing caloric testing of the vestibular pathways?

Back 59

the endolymph of the horizontal canal can be affected by irrigation of ex.auditory meatus.
pt head must be tilted BACK 60 degrees to reach vertical.
(ampulla of horizontal canal is now superior)

warming = rise of endolymph to ampulla (utriculopetal)

cooling = sink of endolymph away from ampulla (utriculofugal).

Front 60

what are higher auditory components?

Back 60

corticogeniculate
corticocollicular
colliculo-olivary
olivocochlear

Front 61

what other systems does the auditory project to? why?

Back 61

superior colliculus (visual), III, IV and VI: reflex turning of head & eyes towards loud sound.

VII and V motor nuclei: stapedius and tensor tympani to dampen amplitude of ear drum and ossicle vibration.

VII motor nucleus: orbiculars oculi, wink at loud sounds.

Front 62

what are some features of the external auditory canal?

Back 62

outer cartilaginous part + inner osseus canal.

cartilaginous: skin attached to perichondrium. epidermis has papillae, hair follicles, sebaceous and apocrine sweat glands.

cerumen: impervious lipid and acid cloak for the skin with anti-bac and anti-fungal action.

Front 63

what are normal flora of the external ear?

Back 63

same as oily skin:

staph epi
micrococcus
corynebacterium
propionibacterium

Front 64

what are the gram negative diseases of the external ear?

Back 64

1.acute diffuse external otitis (p.aeruginosa, proteus vulgaris & fungi)

2.bullous external otitis (hemorrhagic) (p.aeruginosa)

3.granular external otitis (proteus & p.aeruginosa)

4.necrotizing external otitis (p.aeruginosa)

Front 65

what is one of the most common types of ear infections?

Back 65

acute diffuse external otitis (p.aeruginosa or proteus vulgaris and fungi as secondary)

1.hot humid weather
2.itching, pain, fullness
3.green discharge, redness
4.no culture

Front 66

what type of ear infection causes a bloody discharge but is NOT a middle ear infection? how can it be differentiated from a middle ear infection?

Back 66

bullous external otitis has bloody discharge via rupture of bullae on OSSEUS canal walls.

no prior respiratory infection indicates it is NOT a middle ear infection.

Front 67

what can diffuse otitis externa lead to? what are the tell-tale symptoms?

Back 67

1.granular:
skin of meatus is raw, scanty pus and granulations on osseus meatus. DO CULTURE

2.necrotizing:
necrosis on floor of external auditory canal at junction of osseus and cartilage canals. can cause osteomyelitis and meningitis.

Front 68

what are infections of the outer ear caused by gram POSITIVE bactteria?

Back 68

1.furuncle and carbuncle (staph aureus via acute LOCALIZED otitis externa)

2.abscess (s.aureus)

3.cellulitis (strep or staph)

4.erysipelas (grp A beta hemolytic strep)

5.ecthyma (grp A beta-hem strep, some s.aureus as secondary)

6.impetigo contagiosum (" ")

7.infectious eczematoid dermatitis (via PERFORATED otitis media) (s.aureus)

Front 69

what outer ear infections are caused by fungi?

Back 69

saprophytic:
1.acute otomycosis
2.chronic otomycosis

BOTH caused by aspergillus and mucor. chronic conditions may also be the result of dermatophytes, yeastlike fungi, misc fungi and actinomycetes.

pathogenic:
1.candida ostomycosis
2.typical skin parasites, ie malassezia furfur & dermatophytes

Front 70

what is symptomatic of a fungi-outer ear infection?

Back 70

1.hot weather
2.antibiotic/steriod ear drops
3.itchy/full
4.velvet gray pseudomembrane lines skin of meatus & tympanic membrane.
5.wet mount: fungi, neutrophil & epithelial cells.

Front 71

what is candida otomycosis?

Back 71

a pathogenic outer ear fungal ear infection.

1.moisture/maceration
2.immunological compromise
3.antibiotic/corticosteriod
4.redness, edema, pus
5.hyperkeratosis & hyperplasia

Front 72

what are viral outer ear infections?

Back 72

1.herpes simplex
2.herpes zoster
3.verrucae (warts via papovavirus)
4.molluscum contagiosum (poxvirus)

Front 73

name the outer ear infections caused by arthropod parasites.

Back 73

SKIN PROBLEMS, scabies in children/infants.

(ie: wheals, vesicles, bullae)

Front 74

what outer ear diseases are caused by hypersensitivity?

Back 74

1.eczematoid external otitis (delayed, hairspray)

2.photoallergic dermatitis (delayed, soap/sunscreen)

3.atopic dermatitis

Front 75

describe the middle ear.

Back 75

1.simple squamous epithelium
2.communicates with nasopharynx via eustacian
3.lateral: tympanic membrane
4.medial: oval & round windows
5.ossicles

Front 76

why are children's ears easier to infect?

Back 76

children's eustacian tubes (ET) enter the nasopharynx 10 degrees above horizontal, making it easier for infections to enter (adults 45). adult eustacian tubes are also LONGER.

Front 77

eustachian tube is ____ and open near the middle ear; it is _____ near the nasopharynx and the walls are in ______ except when we swallow or yawn.

Back 77

osseus
cartilaginous
apposition

Front 78

what normal flora is found in the middle ear?

Back 78

NONE. but bacteria & viruses may enter via nasopharynx to eustachian tube (lined with lymphoid tissue at this junction).

Front 79

what are the diseases of the middle ear?

Back 79

1.acute suppurative otitis media (> 6wks) (strep pneumonia, h.influenzae, moraxella catarrhalis, grp A strep, s.aureus, some g-rods. maybe nothing!)

2.acute suppurative otitis media NEWBORNS (same as #1, but some neonatal sepsis organisms - staph, chlamydia).

3.chronic otitis media with effusion (OME)
(allergy, virus. bacteria present 1/3 of time, same that cause acute otitis media)

Front 80

what are the major predisposing factors for acute suppurative otitis media?

Back 80

1.previous otitis media
2.URI (dec-march)
3.deviation of ET
4.allergy, day care
5.inverse to breast feeding up to 1 yr old.

Front 81

what is the pathogenesis of acute suppurative otitis media?

Back 81

1.viral URI closes ET
2.negative middle ear pressure = aspired organisms
3.increased middle ear pressure = bulge typmanic membrane.
4.inflammation, lack of drain
5.abnormal patency of ET

Front 82

what are the signs of acute suppurative otitis media? how is it diagnosed and treated?

Back 82

1.ABRUPT pain, fever (not all)
2.unilateral
3.red tympanic membrane
4.moderate leukocytosis
5.spontaneous perforation 24-48 hrs
6.usually do not aspirate fluid, test pressure:
pneumatic otoscope
tympanometry
acoustic reflectometry
7.tylenol, antibiotics
8.myringotomy if needed

Front 83

what sequelae is associated with acute suppurative otitis media?

Back 83

1.fluid in middle ear for wks
2.recurrence, chronic
3.meningitis (rare)

Front 84

when is culture of the otitis media necessary? what are the predisposing factors in this case?

Back 84

acute suppurative otitis media of the newborn requires culture.

predisposing factors:
1.prematurity
2.respirator
3.septic infants born to mothers with prematurely ruptured membranes

Front 85

what type of otitis media infection utilizes 'watchful waiting'? what is it's etiology?

Back 85

chronic otitis media with effusion utilizes watchful waiting. it can be caused by allergy, virus or previous ASOM.
complete obstruction of the ET predisposes one to this infection.

other tx:
myringotomy
tympanostomy tubes
adenoidectomy

rare sequelae: GLUE EAR

Front 86

how is recurrent otitis media defined?

Back 86

more than 3 acute episodes in 6 months.

same etiology as acute otitis media, but s.aureus too (esp w rupture of tympanic membrane).

Front 87

what ear infection requires surgery? what are it's symptoms?

Back 87

chronic otitis media requires surgery. it is caused by anatomic changes in the middle ear cavity that persist even without fluid.

almost always associated with central or anterior perforation and mastoid infection.

skin of ex.auditory canal and surface squamous epi of tympanic membrane may grow thru aperture and invade middle ear.

pus & cholesteatomatous material. usually gram NEGATIVE.

Front 88

what is a disease of the tympanic membrane?

Back 88

bullous myringitis:

inflammation of the lateral surface of the tympanic membrane.

blebs with blood/serous fluid.

etiology: mycoplasma pneumoniae.

Front 89

what types of cells are present in the retina? what do they do?

Back 89

1.photoreceptors:
rods - detect amt of light, night vision.
cones - detect 3 wavelengths, color.

2.interneurons:
horizontal cells
bipolar cells
amacrine cells

3.ganglion cells (collect image info and send to CNS)

Front 90

where does retinal detachment most commonly occur?

Back 90

retinal detachment can occur between the photoreceptor dendrites and the cytoplasmic processes of the pigment epithelium. fluid can accumulate here.

Front 91

what is macular degeneration?

Back 91

macular degeneration is a pathological change which leads to loss of visual acuity in the central part of the field.

Front 92

at the optic chiasm _____ decussate while _____ remain ipsilateral.

Back 92

nasal retinal (decussate)

temporal retinal (ipsilateral)

Front 93

what information does the optic tract carry? the optic nerve?

Back 93

optic tract: HALF image (IL temporal retina + CL nasal retina, aka both left halves or both right halves).

optic nerve: WHOLE image (IL)

Front 94

where do the majority of optic tract fibers project to? minority?

Back 94

majority: (IL)lateral geniculate nucleus

minority: superior colliculus & pretectum

Front 95

what is the lateral geniculate nucleus?

Back 95

1.thalamic relay nucleus for vision.

2.principal target for ganglionic axons from retina.

3.body bulges on ventral diencephalon (below posterior pulvinar nucleus), aka LGB.

4.receives input from visual field corresponding to optic tract.

Front 96

how is the LGN organized?

Back 96

SIX layers from optic tract:

three uncrossed, three crossed. numbered ventral to dorsal.

Front 97

what is the optic radiation? what is it's arterial supply?

Back 97

optic radiation:
the fibers traveling from the diencephalon (LGB) to medial occipital lobe (primary visual cortex). the fibers go thru "c" of lateral ventricle (rostral/inferior horn; caudal/occipital horn).

anterior: MCA (ant.choroidal)
posterior: PCA

Front 98

how is the visual field separated in the geniculocalacrine tract? where is this tract going?

Back 98

EACH PART OF THE GENICULOCALACRINE TRACT IS CARRYING 1/4 IMAGE!

superior visual field travels in meyer's loop (rostral). travels to INFERIOR calacrine cortex.

inferior visual field travels in the caudal optic radiation.
travels to SUPERIOR calacrine cortex.

Front 99

which part of the visual field does the left cortex recieve?

Back 99

the RIGHT visual field (inverted!)

Front 100

how is peripheral and macular vision distributed on the cortex?

Back 100

peripheral: anterior (rostral)

macular: posterior (caudal)

**cortical macular area is proportionately larger than retinal macular**

Front 101

what is BA 17 known as?

Back 101

BA 17 is the primary visual cortex, AKA the striate cortex.

striate: line of gennari, a thickened layer of cortex with mostly myelinated fibers. visible to naked eye!

Front 102

what may cause an optic nerve lesion? what is the effect?

Back 102

1.trauma in orbit
2.increase CSF pressure
3.i carotid, opthalmic a., central retinal a.
4.complete blindness IL

Front 103

what may cause an optic chiasm lesion? what is the effect?

Back 103

1.ischemia
2.midline pituitary tumor
3.tiny bbr of i.carotid a.
4.CENTRAL: bitemporal hemianopia
5.LATERAL: (via bilateral i.carotid dz) binasal heteronymous hemianopia

Front 104

what may cause an optic tract lesion? what is the effect?
what else can cause this effect?

Back 104

1.ischemia via compression/infarction.
2.PCA, PcommA, ant.choroidal
3.R/L homonymous hemianopia

**lateral geniculate lesion causes the SAME effect**

Front 105

what can cause an optic radiation lesion? what are the symptoms?

Back 105

1.vascular compromise
2.MCA, PCA
3.ROSTRAL: R&L upper quadrantanopia
4.CAUDAL: R&L lower quadrantanopia
5.lesion of entire optic radiation: hemianopia

Front 106

what artery is mainly involved with visual cortex lesions? what is the effect of an entire cortex lesion (IL)?

Back 106

PCA supplies the visual cortex. lesion to 1/2 the visual cortex causes R/L homonymous hemianopia.

Front 107

what is macular sparing?

Back 107

macular sparing occurs in some patients suffering cortical blindness. a small central area of acute vision is spared due perhaps to MCA supply or anastamoses of the MCA to the PCA at the occipital pole.

*macular area is projected to the most posterior part of occipital cortex*

Front 108

what would result if BOTH upper/lower banks of the calacrine sulcus were lesioned? what might cause this?

Back 108

upper: lower altitudinopia
lower: upper altitudinopia

*with or w/o macular sparing*

CAUSE: falcine tumor growing laterally to give bilateral effect.

Front 109

what can produce a 'central scotoma'?

Back 109

fall/blow to back of head at occipital pole affects macular vision selectively.

*scotoma: blindness in limited part of retina which is surrounded by normal vision area*

Front 110

what are the autonomic mm of the eye?

Back 110

sympathetic: RADIAL dilator pupillae mm. (radially)

parasympathetic: SPHINCTER pupillae mm. & CILIARY mm (both circularly)

Front 111

when does pupillary dilation occur? how does it happen?

Back 111

1.no light thru optic nerve

2.cortical visual areas output to hypothalamus for dilation (more light let in).

3.sympathetic efferents from hypothalamus descend to upper thoracic, synapsing on pre-g in intermediolateral cell column.

5.descending sympathetics (hypothalamo-spinal) course in LATERAL brainstem tegmentum and LATERAL funiculus of spinal cord.

Front 112

how does contraction of the pupil occur?

Back 112

MIOTIC reaction:
1.afferent limb of reflex includes IL optic nerve, BOTH optic tracts and nuclei.

2.ganglion cells carrying info about light intensity bypass the LGN and synapse on pretectal nuclei in brainstem.

3.pretectal nuclei decussate thru AWC to EW nuclei

4.EW paras run with CNIII to ciliary ganglion

5.postg course thru short ciliary nn to sphincter pupillae.

Front 113

what is lesioned in the case of 'marcus gunn' pupil? what causes this?

Back 113

the AFFERENT limb of the reflex (IL optic nerve, BOTH optic tracts and midbrain nuclei) is lesioned in marcus gunn pupil.

caused by either neuritis or MS.

Front 114

what pupillary reflex lesion is often the result of syphilis?

Back 114

argyll-robertson is often the result of syphilis. location of injury is unknown; tell-tale signs are intact convergence-accomodation & LOSS of pupillary light reflex (no miotic rxn).

why? EW nuclei pathway for miosis is different from the visual c-a pathway.

Front 115

what occurs when focusing on a NEAR object?

Back 115

1.eyes CONVERGE (m.rectus, CNIII)

2.lens THICKENS (ciliary m, ↑ refractive power, EW nucleus + CNIII).

3.pupil CONSTRICTS (sphincter pupillae mm contracts, smaller aperture allows for ↑ depth of focus & field. EW via CNIII).

Front 116

where is the pretectum located? the EW nucleus?

Back 116

pretectum is immediately rostral to the superior colliculus. it projects IL to EW which is just rostral to III nucleus in the superior colliculus.

Front 117

where does the oculomotor nerve exit the brainstem?

Back 117

CNIII exits the brainstem between the cerebral peduncles.

Front 118

name the three ocular mm nuclei and their locations.

Back 118

1.oculomotor: superior colliculus of rostral midbrain. near midline just inferior to periaqueductal gray.

2.trochlear: CAUDAL midbrain, caudal to CNIII nucleus. **decussates**

3.abducens: CAUDAL tectum of pons (floor of 4th ventricle).

Front 119

what are 'vergence' movements? how are they regulated?

Back 119

'vergence' movements are when both eyes move in opposite directions.

vergence center is in rostral midbrain (nuclei + assoc. circuits). BA19, occipital eye field.

convergence: center projects to the two CNIII nuclei controlling abduction.

divergence: relaxation of m.rectus (unopposed l.rectus)

Front 120

what can cause vergence paralysis?

Back 120

vergence paralysis may result from a pineal tumor pressing on the rostral midbrain.

*loss of adduction/convergence = diplopia**

Front 121

where are the horizontal gaze centers?

Back 121

horizontal gaze centers are in the paramedian pontine reticular formation (PPRF).

coordinates conjugate horizontal gaze to SAME side.

PPRF projects to IL CNVI (l.rectus) and CL CNIII (m.rectus; via MLF). PPRF rcvs instruction from 'frontal eye field' (posterior middle frontal gyrus).

contract lr on side looking towards, and mr on opposite side.

Front 122

what is another name for internuclear ophthalmoplegia? what is the cause and effect?

Back 122

MLF syndrome:

1.unilateral lesion

2.can't adduct IL eye when trying to GAZE opposite. CAN adduct during convergence.

3.bilateral MLF syndrome = MS

Front 123

where are the nuclei controlling the vertical conjugate movements? what mm are controlled?

Back 123

vertical gaze center is in the periaqueductal gray matter of the rostral midbrain.

i.oblique, i.rectus(CNIII)
s.oblique (CNIV)

Front 124

what can cause vertical gaze paralysis?

Back 124

PINEAL TUMOR pressing on rostral midbrain. gaze upwards goes FIRST b/c of pressure on tectum.

*parinaud's syndrome: lesion of dorsal midbrain & pretectal area.
upward gaze lost FIRST b/c that part of the vertical gaze center is compressed first.
EW also effected - large pupils.

Front 125

what types of reflexes help keep the eyes fixed on a visual target when the head moves?

Back 125

vestibulo-ocular reflexes. they regulate the conjugate eye movements.

Front 126

how many vestibular nuclei are there? where are they located?

Back 126

4:
superior - caudal pons
lateral, medial and inferior - rostral medulla