Retina & Photoreceptors

What are the two layers of the retina

Pigmented outer layer and inner neural layer

Pigmented layer of retina

outer layer that absorbs light and prevents scattering

Neuro layer of retina

Has photo receptors, bipolar cells, and ganglion cells

(turns light into signal)

Signal pathway in retina

photoreceptors (rods and cones ) (usually graded potential) → transmit signal to bipolar cells → transmit signal to ganglion cells which generates action potential …

What are the two photoreceptors in the retina

cones and rods

Rods -where and good for what

Peripheral regions

night (dim light) + side peripheral vision

fuzzy and colorless (gray tone)W

do rods detect color and why

No → only gray because of rhodopsin pigment which doesnt detect color

Night blindness

impaired rods

Cones -where and good for what

found in macula lutea, concentrated in fovea centralis

good for high acuity (resoluation) vision with color

What does cones need

bright light activiation

Can cones detect color and why

yes

3 primary color pigments - red green blue

Central vs peripheral retina

Central - mecula lutea + fovea centralis → mostly cones → high resolution color vision

peripheral → detecting motion on the side without color → mostly rods

Macular degeneration

damage to macula lutea → loss of central vision

Macula lutea

area of central vision → lots of cones

fovea centralis

center of macula lutea → concentration of cones → highest visual acuity point → best vision → focus point

Optic disc

Where the optic nerve (CN II) exits

no photoreceptors (rods or cones ) → blind spot

Fundus of eye

back interior of eye - only area where doctors can observe small blood vessels

What is more common rods or cones

rods → 120 -130 mil vs 6-7 mil