Lecture 13: Visual System Flashcards by Katlyn Heneghan

_____: A mechanism for protecting the retina from excessive light

Pupillary Light Reflex

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In testing for the pupillary light reflex, illumination in one eye produces ___ constriction of pupils. Illuminated eye gives the ___ response and contralateral eye gives ___ response.
A. unilateral; direct; consensual
B. bilateral; direct; consensual

B. bilateral; direct; consensual

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____ is the central aperture of iris

____ is pigmented disc

_____ is anterior most, avascular and transparent portion of sclera

____ is tough, outermost CT layer

Pupil
Iris
Cornea
Sclera

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What are the three layers of the eye?

Outer: sclera and cornea
Middle: uvea, choroid, cil body, iris
Inner: retina

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True or False: Sclera and Cornea are found in outer eye layer while the Retina is found in the inner most layer

True

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True or False: Cornea and Lens are avascular while Uvea is vascularized

True

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Which of the following is attached to lens via suspensory ligaments and aids in lens accommodation?
A. Choroid
B. Iris
C. Ciliary Body

C. Ciliary Body

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____ is suspended from ciliary body by zonular fibers (suspensory ligaments).
A. Corena
B. Sclera
C. Lens
D. Uvea

C. Lens

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True or False: The zonular fiber that suspend lens from ciliary body helps maintain ellipsoidal shape of lens

True

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The thickness of the lens is controlled by what?
A. Action of zonular fibers
B. Action of muscle in ciliary body

B. Action of muscles in ciliary body

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True or False: Iris is an extension of the choroid

True

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What maintains the shape of the eye?

Intraocular pressure

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_____ is made by body and pushed into anterior and posterior chamber
A. Vitreous humor
B. Aqueous humor

B. Aqueous humor

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____: a gelatinous mass between lens and retina; slow equilibrium
A. Vitreous humor
B. Aqueous humor

A. Vitreous humor

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___ work to accommodate (bring objects into focus)

Lens

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If the ciliary muscles are relaxed and the zonula fibers are under tension, is the lens relaxed or accomodated?

Relaxed

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If the ciliary muscles are contracted and the zonular fibers are relaxed, is the lens relaxed or accomodated?

Accomodated

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True or False: When we are looking at a structure in the distance, our lens is flat; if we are looking at an object up close, our lens is fat

True

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True or False: Iris affects brightness and quality of light entering eye

True

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____: Pigmented disc with central aperture. It contains smooth muscle fibers that regulate size of pupil and, therefore, among of light that reaches retina.

Iris

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True or False: The pupillary sphincter is innervated by parasympathetic fibers from ciliary ganglion and constricts pupil; pupillary dilator is innervated by SYMPATHETIC fibers and contracts muscles to enlarge pupil

True

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True or False: ANS controls pupillary dilation and constriction

True

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Where does optic nerve exit retina?

Via optic disc

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Which structure improves quality of central vision? A. Optic Disc B. Macula C. Retina

B. Macula

True or False: Retina is thicker than fovea

False - retina is thinner

True or False: Fovea is associated with greatest acuity, as it has highest concentration of cones

True

Why is the optic disc called a blind spot?

Lacks photoreceptors

____ is found in the nasal retina while ____ and ___ are found in temporal retina

Optic Disc = Nasal Retina Fovea and Macula Lutea = Temporal

True or False: The outermost layer of the retina contains the rods and cones

True

___: Last link in retinal component of visual pathway. Receive impulse from bipolar cells; its axons join to form optic nerve A. Bipolar Cells B. Muller Cells C. Ganglion Cells

C. Ganglion Cells

____: Dendrites that receive impulse transmission from rods and cones, and axons of these cell synapse with ganglion cells A. Bipolar Cells B. Muller Cells C. Ganglion Cells

A. Bipolar Cells

True or False: Ganglion cell layer is found in innermost retinal layer while photoreceptors are found in outermost retinal layer

True

Light path through retina during visual transduction?

True

True or False: While both rods and cones contain light absorbing photopigments, cones contribute to night vision while while rods contribute to day vision

False - although both do contain light absorbing photopigments, rods contribute to NIGHT vision while cones work during DAYTIME

True or False: Rods are scotopic and more numerous while cones are photopic and less numerous

True

True or False: Pigments are found in outer segment of rods and cones

True

___ are specialized for acuity at the expense of sensitivity. Therefore: we do not see color at low illumination

Cones

Three types of cone pigments?

RBG

Since rods are sensitive to lower levels of light and response for night vision, at lower levels of illumination, we only see ___ and ___

black and white

True or False: The fovea is rich in rods

False - rich in cones

True or False: There are fewer rods and cones in periphery

False - there are more

True or False: Fovea specializes in high light vision, periphery in low light vision

True

True or False: Optic nerve is ensheathed in only 2/3 meninges

False - in 3/3

True or False: Rods are absent from central fovea but increase in periphery of retina

True

How does one acquire papilledema?

Increased intracranial pressure (cerebral edema) causes CSF to compress opthalmic vessel, impede venous drainage, leading to bulge of fluid at optic disc

___ projection carries visual info from eyes to internal structures

Retinofugal projections

When optic nerves join, they create ___ ___

optic chiasm

True or False: Fibers from temporal visual fields (nasal retinas) cross to opposite side

True

What is the net result of this partial decussation of the optic nerve/chiasm?

Left field of vision projects to right side of brain and vice versa

True or False: Both eyes share a visual field

False - each have own

True or False: Since light travels in straight line, there is complete inverse relationship between visual and retinal field

True

True or False: Image in visual field is inverted and reversed onto retina

True

____: center of visual field with image transmitted to fovea of both retinas

Fixation point

Vertical division of retina produces ___ and ___ visual fields A. superior, inferior B. nasal, temporal C. right, left

B. nasal and temporal

Horizontal division of retina produces ___ and ____ visual fields A. superior, inferior B. nasal temporal C. right, left

A. superior, inferior

Right visual field projects to.... A. Right temporal retina/right nasal retina B. Right temporal retina/left nasal retina C. Left temporal retina/right nasal retina

C. Left temporal retina/right nasal retina

Optic nerve fibers partially decussate in ___ ____

optic chiasm

Fibers from temporal retina stay ___ while fibers from nasal retina decussate in chiasm

Ipsilateral

True or False: The entire right visual field projects to the left side of the brain

True

Which condition would you expect to see in one with right monocular field deficit (e.g damage to right optic nerve)? A. Ipsilateral Blindness B. Bilateral Hemianopsia C. Homonymous Hemianopsia

A. Ipsilateral Blindness

Damage to the optic chiasm/pituitary can lead to which condition? A. Ipsilateral Blindness B. Bilateral Hemianopsia C. Homonymous Hemianopsia

B. Bilateral Hemianopsia (loss of lateral visual fields)

Damage to optic tract can lead to which condition? A. Ipsilateral Blindness B. Bilateral Hemianopsia C. Homonymous Hemianopsia

C. Homonymous Hemianopsia (left temporal visual field and left nasal visual field)

Axons of LGN leave LGN to form ____ tract

Geniculocalcarine

What is the relay station for visual info?

Lateral geniculate nucleus of dorsal thalamus

True or False: Striate cortex is the primary visual cortex

True

Incoming LGN axons terminate almost exclusively in layer __ of 6 layered striate cortex. This forms a white line, known as ____

IV (4); Line of Gennari

Fibers from upper visual fields project to cortex __ to calcarine sulcus Fibers from lower visual fields project to cortex ___ to calcarine sulcus

inferior superior

What is the function of the ventral pathway that runs from striate cortex to temporal lobe?

High resolution form vision and object recognition

A dorsal pathway runs from striate cortex to parietal lobe. This system is response for...

Spatial aspects of vision (analysis of motion)

True or False: 80% of fibers sweep laterally and caudally to synapse in LGN of thalamus while 20% enter brachium of superior collicululus

True

____ ____: orients movements of head and eyes ____: reflex control of pupil and lens

Superior Colliculus Pretectum

How do optic radiations (geniculocalcarine tract) maintain retinotopic organization?

Which limb of the pupillary light reflex arc occurs when retinal relays from photoreceptors => bipolar => ganglion cells

Afferent Limb

When cells in pretectal nucleus send axons to both Edinger-Westphal nuclei, which limb of the reflex arc is this? A. Afferent B. Association

B. Association

True or False: Projection to contralteral Edinger-Westphal nucleus decussates in posterior commisure

True

Cells in Edinger-Westphal nuclei send axons via CN III to postganglionic neurons in cilliary ganglia. Which limb of reflex arc is this? A. Afferent B. Association C. Efferent

C. Efferent

Where does the afferent limb terminate?

Tectum

True or False: Pretectum sends axons to both EW nuclei

True

Shining light into one eye causes constriction of both pupils because its ___

consensual

In the efferent limb of reflex arc, ciliary ganglion cells innervate ___ ____ in iris, which results in b/l pupil constriction

sphincter pupillae

If an affected eye shows no direct or consensual response to pupillary light reflect, this suggests lesion to which part of the reflex arc?

Efferent Limb

____: The brain "sees" an out of focus object and reflexively binds it into focus; this reflex requires cerebral cortex

Accommodation Convergence Reflex

Three features of accommodation convergence reflex (aka: near reflex)?

1. Lens thickening 2. Pupillary constriction 3. Ocular convergence

True or False: Argyll-Robertson pupils accommodate and react to light

False - they accommodate but do not react to light

Argyll-Robertson pupils suggest lesion to.... and is specific sign of....

Pretectum; neurosyphillis

What do the mneumonics ARP and PRA mean for Argyll-Robertson pupils?

ARP = Accommodation Reflex present PRA = Pupillary reflex absent