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94 Cards in this Set
- Front
- Back
the image projected onto the retina is ____
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upside down
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layers of the retina?
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what's the fovea look like? what doesn't it have?
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Fovea: there’s no axons no cell bodies..you’ve made the light path as clear as possible (least distortion)-->highest-acuity vision
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cellular components of retina
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difference bw rods and cones?
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Disks in outer segmentdisks for surface area…capturing light
Have molecules that transduce light Rods have more disks-->they function in dark…so that’s why they have more disks to capture as much light as possible RODS Scotopic: Low light levels Monochrome: Single wavelength CONES Photopic: High light levels Color vision: Three wavelengths |
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Cones are less sensitive to light than the rod cells in the retina (which support vision at low light levels), but allow the perception of color.
Because humans usually have three kinds of cones, with different _____, which have different response curves, and thus respond to variation in color in different ways, they have trichromatic vision. |
photopsins
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what the photoreceptor distribution of the retina?
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cones concentrated in the middle....rods decrease in the retina's periphery
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when photoreceptors are activated, they become depolarized/hyperpolarized
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hyperpolarized!
opp of what you would accept in the dark, they are activated.. |
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photoreceptor membrane potential is a balance bw
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in the dark, which of the 2 currents dominate?
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in the light, what happens to the currents in the photoreceptor
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how is light transduced in photoreceptors?
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Light captured by rhodopsin (which is an G-protein associate receptor)….transducin (G-protein) activates cGMP phopodiesterase-->dec cGMP--> closing up cGMP-gated Na+ channels
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what is this?
what family of proteins does it belong to? what molecule is it associated with? |
rhodopsin
G-protein coupled receptor it's associated with the G-protein transducin |
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“As a chromophore, ____ has covalently bound in its inactive dark state ____, which isomerizes after photon capture to an _____ This initial structural change within the chromophore binding pocket is propagated to the cytoplasmic surface of the receptor, enabling the docking and activation of downstream elements of the signal transduction cascade, as G protein, kinases, and arrestin.”
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rhodopsin
11-cis retinal all-trans geometry. |
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Set up center-surround receptive field properties bymodulating photoreceptorpotentials
“Integrate” light signalsover a variable area |
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Midget retinal ganglion cells project to the ______ layers of the ______These cells are known as midget retinal ganglion cells, based on the small sizes of their dendritic trees and cell bodies. About 80% of RGCs are midget cells in the parvocellular pathway.
They receive inputs from relatively few rods and cones. In many cases, they are connected to midget bipolars, which are linked to one cone each. They have slow conduction velocity, and respond to changes in color but respond only weakly to changes in contrast unless the change is great. They have simple center-surround receptive fields, where the center may be either ON or OFF while the surround is the opposite. |
parvocellular
lateral geniculate nucleus. Midget Ganglion Cell Red/Green Small RFs Central visual field Spatial opponency |
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Parasol retinal ganglion cells project to the _____layers of the lateral geniculate nucleus. These cells are known as parasol retinal ganglion cells, based on the large sizes of their dendritic trees and cell bodies. About 10% of retinal ganglion cells are parasol cells in the magnocellular pathway. They receive inputs from relatively many rods and cones. They have fast conduction velocity, and can respond to low-contrast stimuli, but are not very sensitive to changes in color. They have much larger receptive fields which are nonetheless also center-surround.
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magnocellular
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tell me the pathway of aqueous humor?
Intraocular pressure is a function of production of liquid aqueous humor by the ___body of the eye and its drainage through the _____. Aqueous humor flows from the _____ into the ____ CHAMBER, bounded posteriorly by the lens and the zonule of Zinn and anteriorly by the iris. It then flows through the pupil of the iris into the ____CHAMBER, bounded posteriorly by the iris and anteriorly by the cornea. From here the TRABECULAR NETWORK drains aqueous humor via ____ into scleral plexuses and general blood circulation. In open angle glaucoma there is reduced flow through the trabecular meshwork; in angle closure glaucoma, the iris is pushed forward against the trabecular meshwork, blocking fluid from escaping. |
ciliary
trabecular meshwork CILIARY BODY POSTERIOR ANTERIOR SCHLEMM'S CANAL |
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treatment for glaucoma?
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2 types of glaucoma?
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Open angle= reduced drainage through canal. Not painful.
Closed angle= iris pressing against trabecular meshwork, blocking fluid from draining. Painful. angle =angle bw the iris and the cornea |
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how to decrease aqueous humor production?
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Activation of Beta1 receptors increases aqueous humor production.
--Timolol (beta blocker) will decrease aqueous humor production Beta agonists will make things worse Alpha2 agonists (negative feedback, so decreased sympathetic tone) will decrease activation of beta receptors and therefore also decrease aqueous humor production |
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how to increase drainage?
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A dilated pupil restricts outflow, a constricted pupil increases outflow.
---Parasympathetics constrict pupil ---Sympathetics (via alpha1 receptor) dilate pupil Alpha1 blockers Cholinomimetics (pilocarpine) or AchE inhibitors (physostigmine) Alpha1 agonists (phenylephrine) and muscarinic antagonists (atropine) dilate pupil -> make things worse |
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the optic radiation includes what 2 parts?
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Myer's loop (goes through temporal lobe)
and the part that goes through parietal lobe If Meyer's loop is lesioned, the vision loss is superior; if the parietal path is lesioned, the vision loss is inferior. Just remember MEYER= SUPERIOR VISUAL FIELD PARIETAL PATH= INFERIOR VISUAL FIELD Top retina (inferior visual field)goes in the parietal lobe…(shorter path) Bottom retina (superior visual field) goes in the temporal lobe (longer path..more susceptible to damage) |
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the optic radiation includes what 2 parts?
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Myer's loop (goes through temporal lobe)
and the part that goes through parietal lobe If Meyer's loop is lesioned, the vision loss is superior; if the parietal path is lesioned, the vision loss is inferior. Just remember MEYER= SUPERIOR VISUAL FIELD PARIETAL PATH= INFERIOR VISUAL FIELD Top retina (inferior visual field)goes in the parietal lobe…(shorter path) Bottom retina (superior visual field) goes in the temporal lobe (longer path..more susceptible to damage) |
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draw the visual field of each eye (the circles):
name of defect: can be caused by: |
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Central Scotoma
caused by: |
Optic Neuritis
macular degeneration |
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glaucoma
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draw visual fields of both eyes (seriously!)
name of lesion: can be caused by: |
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visual fields of both eyes:
name of defect: can be caused by: |
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visual field of both eyes:
name of lesion: can be caused by |
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In the human fovea the ratio of ganglion cells to photoreceptors is close to ___;
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1
almost every photoreceptor has one ganglion cell receiving data from it. That is why it has little loss of sensory data, thus it is the area of the eye where most details can be seen. Starting at the outskirts of the fovea, however, rods gradually appear, and the absolute density of receptors progressively decreases. The human fovea has a high concentration of cone photoreceptors. The centre of the fovea is the foveola - about 0.2 mm in diameter - where only cone photoreceptors are present and there are virtually no rods |
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The fovea is the center most part of the ____ .It is the center of the eye's sharpest vision and the location of most color perception.
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macula
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how many cones?
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6 million
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how many rods?
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120 million
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output pathways from the retina?
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cells of V1?
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phototransduction?
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receptor fields of ganglion cells? what is the type?
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center-surround
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types of cells in the retina?
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light pathway:
start from light and end in primary visual cortex-->dorsal/ventral streams |
Light => cornea (focus) => aqueous humor => pupil => lens (adjustable focus) => vitreous humor--> photoreceptors (rods, cones) at the back of the retina (outer nuclear layer)--> bipolar cells (inner nuclear layer) => ganglion cells; M, P, K cells sending axons to...-->optic nerve->LGN (thalamus)->optic radiation (2 parts, Myer's loop + parietal pathway)-->V1 (primary visual cortex aka striate cortex, = Brodmann area 17)-->dorsal/ventral stream
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Which movement does NOT utilize MLF? With head still, Looking at your..
(a) R leg (b) L arm (c) L eyebrow (d) nose |
nose
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Light in L eye: only L pupil contracts. Light in R eye, BOTH pupils contract
Motor or sensory deficit? Where? (a) Motor nucleus (b) motor axon (c) CN II (d) E-W |
E-W
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Fovea –
-spot on retina corresponding to center of visual field - has the highest visual acuity, highest density of ____ - lots of cones => great daytime/color vision, poorer nighttime vision - overrepresented (size-wise) in post. visual cortex (analogous to fingertips in S1) |
photoreceptors
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what are opsins?
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-proteins that determine the spectum of light selectivity to which a photoreceptor responds
- Retinal (from vitamin A) is the light sensing component - G Protein Coupled, activates cGMP phosphodiesterase [PDE] - cGMP gated ion channels let in Na/Ca/Mg, these are active in the dark - activation of cGMP PDE => decrease in cGMP => close channels - thus, light causes a DECREASE in neurotransmitter release |
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Rhodopsin consists of the protein moiety ___ and a reversibly covalently bound cofactor,
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opsin
retinal |
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All ganglion cells are ____until the optic nerve
(maximize light getting through to photoreceptors) |
unmyelinated
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what's the optic disk?
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The LGN receives information directly from the ascending______ via the optic nerve and from the reticular activating system.
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retinal ganglion cells
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how many layers of the LGN? with which ganglion cells do they correspond?
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6 layers
- 1-2 are Magnocellular (two largest layers at bottom) - 4-6 are Parvocellular - Intralaminar Layers are Koniocellular - Layers 1, 4, 6 from contralateral eye - Layers 2, 3, 5 from ipsilateral eye [Can I C with two I’s Closed?] |
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Visual cortex = primary visual cortex +
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extrastriate visual cortical areas such as V2, V3, V4, and V5.
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Primary Visual Cortex aka___Cortex, V1, Area
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Striate
17 |
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where's our blind spot?
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the dorsal and ventral stream pathways?
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The ventral stream begins with V1-->V2,-->V4 --> temporal lobe
"___ Pathway", is associated with form recognition and object representation. It is also associated with storage of long-term memory.(Trees > forest) -input from all three cell types -Less concerned with position in space or orientation |
What (as in vat?? for ventral stream)
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Damage to ventral stream?
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Agnosia (can’t recognize objects)
--- Proposagnosia – inability to recognize faces ventral stream= vat pathway= form recognition and object representation |
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MLF is the main pathway that connects the ____ and ____nuclei with the nuclei controlling the extraocular muscles (3, 4,6)
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vestibular
cochlear MLF yokes the cranial nerve nuclei III, IV and VI together, and integrates movements directed by the gaze centers (frontal eye field) and information about head movement (from cranial nerve VIII). It is an integral component of saccadic eye movements as well as vestibulo-ocular and optokinetic reflexes. It also carries the descending tectospinal tract and medial vestibulospinal tracts into the cervical spinal cord, and innervates some muscles of the neck and upper limbs. |
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______ is paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation
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Cycloplegia
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______ is a condition in which the eyes are not properly aligned with each other.
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Strabismus
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_____is a form of strabismus, or "squint", in which one or both eyes turns inward
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Esotropia
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is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye. .
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Amblyopia
Amblyopia is a developmental problem in the BRAIN, NOT an organic problem in the eye (although organic problems can induce amblyopia which persist after the organic problem has resolved). The part of the brain corresponding to the visual system from the affected eye is not stimulated properly, and develops abnormally. (recall the 'critical period') |
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The center-surround receptive field organization allows ganglion cells to transmit information not merely about whether photoreceptor cells are exposed to light, but also about the differences in firing rates of cells in the center and surround. This allows them to transmit information about contrast. The size of the receptive field governs the spatial frequency of the information: ____ receptive fields are stimulated by high spatial frequencies, fine detail; ____receptive fields are stimulated by low spatial frequencies, coarse detail.
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small
large |
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Frontal eye fields (FEF) is a gaze center in the _____that directs horizontal gaze _____
Paramedian pontine reticular formation (PPRF) is a gaze center in the ____that directs horizontal gaze ______ • Lesions in the frontal lobe causes gaze to look towards the lesion (the opposite FEF is unopposed) • Lesions in the brainstem causes gaze to look away from lesion (the opposite PPRF is unopposed) |
frontal cortex, contralaterally
brainstem , ipsilaterally. |
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Frontal eye fields projects directly to the _____PPRF
thus, Frontal eye fields (FEF) directs (horizontal) gaze contralaterally |
contralateral
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what connects the abducent and the oculumotor nuclei---imp for gaze coordination
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MLF!
medial longitudinal fasciculus |
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____ is a type of strabismus in which one or both eyes turn inward, while
____ is a type of strabismus in which one or both eyes turn outward. If congenital and not corrected, due to the critical period, either can lead to _____. |
Esotropia
exotropia ambylopia |
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PUPILS
unequal pupils, at rest without stimuation, the pupil size in the one eye is different than in the other. |
anisicoria:
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PUPILS
No direct or consensual reflex, but DO have accommodation-convergence intact. Seen in neurosyphilis (last stage of untreated syphilis). |
Argyll-Robertson pupil
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PUPILS
Dilated pupil, reacts sluggishly to light, but better to accommodation. |
Adie pupil:
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Raised ICP leads to _____(uncus herniates across tentorium), CNIII compressed, creating a fixed and dilated pupil. Also, eye is positioned down and out" due to unopposed action of CN IV and CN VI.
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transtentorial uncal herniation:
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PUPILS
Afferent limb of reflex is damaged. Diagnosed with swinging-flashlight test, by which a light is shined in DAMAGED pupil: pupils do not constrict. Shine light in INTACT pupil: both pupils constrict fully. |
Marcus-Gunn pupil
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Horner syndrome
name 4 symptoms |
1. miosis (pupil CONSTRICTION. remember, sympathetics cause mydriasis -- pupil DILATION -- but, it you LOSE sympathetics, you get miosis).
2. Anisocoria -- this means 'unequal pupils.' This can happen in myriad diseases, and can even be normal. Because the lesion happened on one side (the side that his tumor is compressing on his sympathetic trunk), you would expect that pupil to be constricted, and the other to be normal, therefore, the patient has anisocoria. 3. anhidrosis (lack of sweating) on the side of the lesion, due to sympathetic loss. Hyperhidrosis is EXCESSIVE sweating, and would NOT happen in a loss of sympathetics. 4. ptosis (eyelid droop): drooping upper eyelid from loss of sympathetic innervation to the Müller (superior tarsal) muscle. |
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Horner syndrome is due to a deficiency of _____ activity. The site of lesion to the sympathetic outflow is on the _____ side of the symptoms. The following are examples of conditions that cause the clinical appearance of Horner's syndrome:
• First-order neuron disorder: Central lesions that involve the hypothalamospinal pathway (e.g. transection of the cervical spinal cord). • Second-order neuron disorder: Preganglionic lesions (e.g. compression of the sympathetic chain by a lung tumor). • Third-order neuron disorder: Postganglionic lesions at the level of the ______ (e.g. a tumor in the cavernous sinus). |
sympathetic
ipsilateral internal carotid artery |
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If someone has impaired sweating above the waist affecting only one side of the body, yet they do not have a clinically apparent Horner's syndrome, then the lesion is just below the _____ ganglion in the sympathetic chain.
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stellate
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There are two common 'MS' visual lesions:
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optic neuritis and INO
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name the artery that supplies:
Optic chiasm/tract |
ACA and ICA
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name the artery that supplies
LGN |
PCA and anterior choriodal (most often off ICA)
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what supplies the optic radiations:
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MCA
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what supplies V1:
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PCA
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which artery supplies the occipital pole (absolute tip of occipital lobe):
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MCA and PCA
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Name the artery that supplies:
Optic chiasm/tract: LGN: optic radiations: V1: occipital pole (absolute tip of occipital lobe): |
Optic chiasm/tract: ACA and ICA
LGN: PCA and anterior choriodal (most often off ICA) optic radiations: MCA V1: PCA occipital pole (absolute tip of occipital lobe): MCA and PCA |
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PCA infarct
What can be lost? |
- The LGN is spared by the fact that the anterior choroidal can supply blood.
- But, he still loses a large part of V1. This produces a contralateral homonymous hemianopia. - But, the macular/foveal region of the occipital lobe is 'rescued' or 'spared' by the fact that it gets blood from the MCA in addition to the PCA. Therefore, when there is a contra homonymous hemianopia, there is also macular sparing, and the region of highest visual acuity (macula and fovea are intact). |
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MCA infarct would affect what?
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Since the MCA supplies the optic radiations, and they together (Meyer and parietal loop) produce a contralateral homonymous hemianopia, then that is the lesion: contralateral homonymous hemianopia (and includes the macula/foveal area as well).
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what's this?
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blind spot aka scotoma
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pituitary tumor: compression of medial optic chiasm produces_____vision, called_____
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tunnel
bitemporal hemianopia |
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t/f
a lesion of the optic tract, LGN, or visual pathway to V1 produce SAME deficit: contra homonymous hemianopia |
true
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The fovea defines the center of the retina, and is the region of highest visual acuity. The fovea is directed towards whatever object you wish to study most closely - this sentence, at the moment. In the fovea there are almost exclusively cones, and they are at their highest density.
The ratio of ganglion cells : photoreceptors is about 2 :1 here, the highest in the eye. In addition, at the fovea all of the other cell types squeeze out of the way to allow the most light to hit the cones. This makes the fovea visible microscopically. The blood vessels also skirt a wide margin around the fovea. The area in and around the fovea has a pale yellow pigmentation that is visible through an ophthalmoscope, and is called the ____ |
macula.
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- The cornea is continuous with the ____, which in turn is continuous with the dura.
- The ____, a highly vascular, highly pigmented layer between the sclera and the retina, is continuous with the ciliary body and the iris. Do not confuse it with the pigment epithelium. - The _____ is a single cell layer thick, and comes from the outer layer of the original optic cup (a classic embryological "pushed-in ball"). In the mature retina it is pushed directly up next to the neural retina, which came from the inner layer of the optic cup. They are not fused together, however, and can separate along the old plane - a "separated" or "detached" retina. |
sclera
choroid pigment epithelium |
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Of the 2 types of photoreceptors, the ___ are more sensitive to low-intensity light and therefore are more important than the cones for night vision.
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rods
They adapt to darkness after the cones, which are primarily involved in color vision. |
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Rods are not present in the
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fovea.
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Light converts 11-cis retinal to _____, which is converted to intermediates such as metarhodopsin II. Metarhodopsin II activates a stimulatory G protein (_____) which activates a phosphodiesterase. Phosphodiesterase breaks down cyclic guanosin monophosphate (cGMP) so intracellular cGMP levels decrease, causing closure of Na+ channels in the photoreceptor cell membrane and ______
Hyperpolarization inhibits release of neurotransmitter. If the neurotransmitter is excitatory, then the bipolar cell will be hyperpolarized (inhibited). If the neurotransmitter is inhibitory, then the bipolar cell will be depolarized (excited). |
all-trans retinal
transducin hyperpolarization. |
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Simple and complex cells (both of the visual cortex) respond to moving bars or edges with the correct _____
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orientation.
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