Vision I: The Eye

In reflection, light bounces off at the ____ angle it incidences at.

same

In absorption, light is completely ________ by an object.

absorbed

In refraction, light _____ due to the speed at which light travels in different mediums.

bends

Images form in the eye via __________.

refraction

What is the focal point?

where all the light beams converge

What is a convex lens also known as?

a converging lens

What is a concave lens also known as?

a diverging lens

The lens of the eye is ________.

biconvex

Light from a point source has a _______ focal length than light from a distant source.

smaller

What size lens has the highest refractive power and a short focal length?

thick lens

What’s the orientation of the image that’s generated by the biconvex lens?

upside down

What are the visible spectrum wavelengths in the EM spectrum?

380nm-750nm

Going from 380nm-750nm, what’s the order of colors?

VIBGYOR

What receptors are used in the visual system?

photoreceptors, rods and cones

Where does sensory reception occur?

photoreceptors

Where does sensory transduction occur?

photoreceptors

Where does sensory transmission occur?

optic nerve

Where does sensory perception occur?

visual/striate cortex

Pathway of visual info transmission:

• retina

• optic nerve

• optic tract

• optic chiasm

• hypothalamus (autonomic fx, circadian rhythm)

• LGN

• optic radiation

• striate/visual cortex

What is the pupil?

opening where light enters the eye

What is the iris?

colored muscles

How many sets of muscles in the iris?

2

Which part of the eye is primarily involved in the pupillary light reflex?

iris

What is the cornea?

• glassy transparent external surface, continuous with sclera

• in front of the pupil/iris

What is the sclera?

tough, white fibrous tissue

What is the outermost layer of the eye (excluding the cornea in the front)?

sclera

What is the conjuctiva?

• membrane that folds back from the inside of the eyelids

• attaches to the sclera

What is the optic nerve?

bundle of axons coming from the retina

What are the extraocular muscles?

• 3 pairs of muscles

• voluntary and reflexive movement

Which extraocular muscles are responsible for up and down movement?

• superior rectus (up)

• inferior rectus (down)

Which extraocular muscles are responsible for side to side movement?

• medial rectus (inward)

• lateral rectus (outward)

Which extraocular muscles are responsible for diagonal movement?

• superior oblique (down/out)

• inferior oblique (up/out)

Which way does the superior oblique muscle move the eye?

down/out

Which way does the inferior oblique muscle move the eye?

up/out

What’s the function of the ciliary muscle?

adjusts lens size (accommodation)

Which part of the eye is the only part that contains neurons that are sensitive to light?

retina

Which part of the eye is actually part of the CNS?

retina

What’s the function of the cornea?

permits light entry

What’s the shape of the lens?

biconvex

What’s the function of the lens?

refracts light to focus images on the retina

What part of the eye can stretch and relax for accommodation?

lens

What is the aqueous humor?

clear watery liquid

What’s the function of the aqueous humor?

supplies nutrients to cornea and lens

What produces the aqueous humor?

ciliary processes in the posterior chamber

Where is the aqueous humor?

anterior chamber

How does the aqueous humor get from the posterior to anterior chamber?

through the pupil

What is the vitreous humor?

thick, gelatinous substance

What’s the function of the vitreous humor?

maintains the shape of the eye

What cells in the vitreous humor are capable of removing blood and debris from the eye?

phagocytes

What are zonule fibers?

fibers connecting the lens to the ciliary muscles

In the parasympathetic NS, the ________ muscles of the eye _________.

circular, constrict

In the sympathetic NS, the ________ muscles of the eye _________.

radial, dilate

What’s the neurological pathway of the oculomotor nerve?

• oculomotor nucleus

• oculomotor nerve

• extraocular muscles

Which CN are involved in eye movement?

• oculomotor

• trochlear

• abducens

Which ganglion does the sensory division of the oculomotor nerve go through?

ciliary ganglion

What structures does the visceral motor pathway (accommodation, pupil size) of the oculomotor nerve involve?

• edinger westphal nucleus

• ciliary ganglion

• circular muscles

• ciliary muscles

What is accommodation?

changing the shape of the lens to enable us to focus at different distances

When the zonule fibers are taut, the lens is ____, and ___ is in focus.

long, far

When the zonule fibers are relaxed, the lens is ____, and ___ is in focus.

short, close

At _m away, the lens and ciliary body are in a neutral position.

6

Which brain vesicle turns into the retina?

optic vesicle of the diencephalon

What’s the organization of the retina from inside to outside?

• (inside)

• pigmented epithelium

• photoreceptors

• outer nuclear layer

• outer plexiform layer

• inner nuclear layer

• inner plexiform layer

• ganglion cell layer

• nerve fiber layer

• (outside)

What’s the organization of the cells in the retina from inside to outside?

• (inside)

• photoreceptors

• bipolar, horizontal, amacrine cells

• ganglion cells

• (outside)

What’s the function of the pigmented epithelium?

absorbs light that makes it all the way to the back of the eye (minimizes reflections within the eye)

What are photoreceptors?

rods and cones

What are bipolar, horizontal, and amacrine cells?

local circuit neurons

What are ganglion cells?

projection neurons

The axons of the ganglion cells form….

the optic nerve

What are ganglion cells also known as?

retinal ganglion cells (RGCs)

What’s the flow of information in the retina?

• light activates photoreceptors

• photoreceptors transduce light into APs

• synapse onto bipolar, amacrine, horizontal cells

• bipolar, amacrine, horizontal cells synapse onto ganglion cells

• ganglion cells form optic nerve

• optic nerve transmits signals to the brain

What is the outer nuclear layer?

cell bodies of photoreceptors

What is the outer plexiform layer?

synapses between photoreceptors and bipolar, amacrine, and horizontal cells

What is the inner nuclear layer?

cell bodies of bipolar, amacrine, and horizontal cells

What is the inner plexiform layer?

synapses between bipolar, amacrine, horizontal cells and ganglion cells

What is the ganglion cell layer?

cell bodies of ganglion cells

What are the first true neurons in the flow of information in the retina?

ganglion cells

What is the nerve fiber layer?

axons of ganglion cells forming the optic nerve

What does plexiform mean?

network like

What’s the anatomy of the outer segment?

stacks of disks containing photopigments

Which specific structure in the photoreceptors are responsible for transduction?

photopigments

Which part of the photoreceptor is the location of transduction?

outer segment

What are the disks of the outer segment?

infoldings of the cell membrane containing photopigments

What’s the anatomy of the inner segment?

cell body with nucleus

What happens at the synaptic terminal of a photoreceptor?

glutamate is released onto bipolar and horizontal cells

What cells do photoreceptors synapse onto?

bipolar and horizontal cells

What is spatial resolution?

the ability to tell 2 points apart (e.g. 720p, 1080p, 4k)

What photopigment is used in rods?

rhodopsin

What light conditions do rods respond to?

low-light conditions

What type of vision do rods support?

black and white, night vision

What’s the convergence of rods to ganglion cells (high or low)?

high

How many rods converge onto one ganglion cell?

MANY

Do rods have good or bad spatial resolution?

bad

Why do rods have bad spatial resolution?

high convergence (many rods: 1 ganglion cell)

What happens when you lose rod function?

trouble seeing in low light (night blindness)

What is it called when you struggle to see in low light conditions due to rod failure?

night blindness

What photopigment is used in cones?

opsin

What wavelength and color does L-opsin detect?

• long wavelengths

• red

What wavelength and color does M-opsin detect?

• medium wavelengths

• green

What wavelength and color does S-opsin detect?

• short wavelengths

• blue

What light conditions do cones respond to?

bright light conditions