Lectures 3 & 4 (light and the retina)

Question 1

What is light?

Answer 1

Electromagnetic radiation that travels in waves

Question 2

How does light exhibit dual nature?

Answer 2

WAVE LIKE PROP. Wavelength determines color
PARTICLE LIKE PROP. Photons carry energy

Question 3

How do frequency, wavelength and energy interelate?

Answer 3

Short wavelength –> high freq. high energy
long wavelength—> low freq, low energy
(high energy, eg. UV, can cause damage to humans and biological life forms)

Question 4

How big is the visisble light spectrum

Answer 4

small, 400-700 nm

Question 5

Wavelengths and color

Answer 5

Short, blue
long, red

Question 6

Why do we need optics?

Answer 6

Because it means we have image-forming eyes instead of just light-detecting

Question 7

What are the 4 optical components to focus light?

Answer 7

> CORNEA (primary focus)
AQUEOUS HUMOR (fluid for nutrients and pressure)
LENS (focus via accommodation- dynamically, refraction)
VITREOUS HUMOR (gel- creates shape)

Question 8

Emmetropia

Answer 8

Normal vision, eyes optics focus light directly on to the retina

Question 9

Myopia

Answer 9

Nearsightedness, eye is TOO LONG, light gets focused INFRONT of retina
> CONCAVE req.

Question 10

Hyperopia

Answer 10

Farsightedness, eye is TOO SHORT, light is focused behind retina
> CONVEX req.

Question 11

Astigmatism

Answer 11

uneven cornea curvature (distortion at multiple distances)

Question 12

Presbyopia

Answer 12

Lens less flexible with age, close objects harder to see

Question 13

Cornea

Answer 13

Primary focal area

Question 14

Aqueous humor

Answer 14

Fluid that maintains nutrients and pressure

Question 15

Iris/pupil

Answer 15

Contracts/dilates to allow more or less light in

Question 16

retina

Answer 16

Converts light into neural signals through photoreceptors thru optic nerve

Question 17

Lens

Answer 17

Focus via accommodation

Question 18

What are the key structures of the retina?

Answer 18

> Macula (Central region, high visual activity)
Fovea (extra cones, sharp vision)
Optic disc (blind spot where optic nerve exits the eye)
Pigment epithelium (absorbs stray light, prevents scattering)

Question 19

Why is the retina “backwards”

Answer 19

Whatever lee rachel said is correct she knows this for sure

Question 20

What are ganglion cells

Answer 20

the cells in the front of the retina that send signals to the brain

Question 21

Rods vs. Cones

Answer 21

RODS
> low-light (scotopic)/night vision
> do NOT detect color
> highly sensitive
> peripheral retina
CONES
> three types, S, M, L, for color perception
> high acuity (sharpness)

Question 22

Scotopic vision meaning

Answer 22

Low light/night vision

Question 23

Describe photo receptor density across the retina

Answer 23

Optic disc - blind spot, no rods or cones
Fovea: fuck ton of Cones, no rods
Rods everywhere else

Question 24

Foveal vs. Peripheral Vision

Answer 24

FOVEAL
> low CONVERGENCE (each cone connects to a single ganglion cell
> cones only
> FINE DETAIL & HIGH RES
> Focus, detail, FACIAL RECOGNITION

PERIPHERAL
> high CONVERGENCE
> rods
> MOTION SENSITIVITY
> NIGHT VISION

Question 25

What does retinal convergence refer to?

Answer 25

The amount of ganglion cells a photoreceptor connects to

Question 26

What is the vertical pathway in the retina?

Answer 26

PHOTORECEPTORS --> BIPOLAR CELLS ---> GANGLION CELLS (fire action potentials) ----> LGN (brain)

Question 27

What is the Horizontal pathway in the retina?

Answer 27

HORIZONTAL CELLS: Help sharpen contrast by fucking up their neighbors (not Christian) AMACRINE CELLS: Fine-tune the ganglion cells' signals before they leave

Question 28

The other names for Vertical and horizontal pathways in the retina

Answer 28

vert: Direct signal transmission hor: Lateral inhibition

Question 29

Retinal pathways

Answer 29

M-Pathway (magnocellular, Large Cells) > PERIPHERY P- Pathway (Parvo cellular, small cells) > FOVEA

Question 30

What are the main mechanisms of luminance adaptation?

Answer 30

>Pupil dilation/constriction >photopigment regeneration >Duplex retina > Neural circuitry organization (convergence)

Question 31

What is photopigment regeneration

Answer 31

Light exposure beaches photopigments ---> temporarily reducing sensitivity Regen. in darkness, improving night vision over time

Question 32

What does it mean that we have a duplex retina

Answer 32

Rods and cones

Question 33

What are the strengths and weaknesses

Answer 33

Strength: >Can stimulate surviving ganglion cells in blind people Weaknesses: >Must have ganglion cells intact >Not full vision, not color vision >low res (few electrodes = few pixels)