NE101 Lec 13: Vision I

Focuses on eye anatomy, light transduction, and visual processing.

sensory transduction

convert external modality into electrical charges

what part of the eye is this?

zonule fibers

what part of the eye is this?

iris

what part of the eye is this?

pupil

what part of the eye is this?

cornea

what part of the eye is this?

lens

what part of the eye is this?

ciliary muscle

what part of the eye is this?

retina

what part of the eye is this?

fovea

what part of the eye is this?

optic disk

what part of the eye is this?

optic nerve

what part of the eye is this?

vitreous humor

what direction of the eye is this?

anterior

what direction of the eye is this?

posterior

refraction

bending of light from one medium (air) to another (water/glass/tissue)

focal distance

distance between the cornea and the retina at which light rays converge

ciliary muscle function

controls lens shape

_____ determines how light is bent

lens thickness

what is accomodation?

the process of changing the lens to focus on things closer or farther away

Humans can see wavelengths from about ________ to ________ nm.

400 to 750

The ________ and ________ focus light on the retina.

cornea, lens

The retina contains ________ that transduce photons into neuronal activity.

photoreceptors

The retina sends signals through the ________ nerve (CN II).

optic

The ________ is the region of the retina with the highest visual acuity.

fovea

A long, thin lens bends light ________ and focuses on ________ objects.

less, far

A short, thick lens bends light ________ and focuses on ________ objects.

more, near

When ciliary muscles are relaxed, the lens becomes ________.

thin

When ciliary muscles contract, the lens returns to its ________/normal shape.

thick

Hyperopia (farsightedness) occurs when the eyeball is too ________.

short

Hyperopia requires a ________ lens to converge light.

convex

Myopia (nearsightedness) occurs when the eyeball is too ________.

long

Myopia requires a ________ lens to diverge light.

concave

Pupil constriction occurs in ________ light and is controlled by the ________ nervous system.

bright, parasympathetic

Pupil dilation occurs in ________ light and is controlled by the ________ nervous system.

dim, sympathetic

Constriction allows ________ light in and ______ depth of focus.

less, increases

Dilation allows ________ light in but ______ depth of focus.

more, decreases

The retina is part of the ________ nervous system.

central

The ________ is the center of the visual field on the retina.

fovea

The ________ spot contains no photoreceptors.

blind

The blind spot doesn’t affect vision much because of ________ vision.

binocular

The outer segment of photoreceptors is where ________ occurs.

transduction

_____ are more sensitive to light but do not detect color.

rods

______ are less sensitive to light but detect color.

cones

Near the fovea, there are more ________, giving high color and spatial resolution.

cones

Away from the fovea, there are more ________, giving better low-light sensitivity.

rods

Photoreceptors have a resting potential around ________ mV.

-30

Sodium channels in photoreceptors are activated by ________.

cGMP

Light exposure ________ cGMP, closing sodium channels and ________ the cell.

reduces, hyperpolarizes

Photoreceptors release ________ in the dark and less of it in the light.

glutamate

______ is a g-coupled receptor that acts as a photosensor.

rhodopsin

When light hits rhodopsin, it activates the G-protein ________.

transducin

Light → retinal change → transducin activation → ↓cGMP → ________ close → membrane hyperpolarizes.

sodium channels

Short cones detect ________ light, medium cones detect ________ light, and long cones detect ________ light.

blue, green, red

Color vision results from activation of different ________ of cones.

proportions

Each cone type has a distinct ________ protein.

photosensor

Color blindness results from dysfunction or absence of specific ________ receptors.

cone

About ________% of the population is affected by color blindness.

5

Photoreceptors and bipolar cells fire ________ potentials.

graded

Only ________ cells in the retina fire action potentials.

retinal ganglion

On-center bipolar cells are ________ when light hits the center of their receptive field.

depolarized

Off-center bipolar cells are ________ when light hits the center.

hyperpolarized

The receptive field is the region of visual space that a cell ________ to.

responds

On-center retinal ganglion cells increase firing when light hits the ________ of their receptive field.

center

Off-center retinal ganglion cells increase firing when light hits the ________.

surround

On-center and off-center organization helps detect ________ in light intensity and contrast.

changes