Retina and optic nerve

Question 1

Identify the different layers and cell types in the retina and their functions

Answer 1

Outer -> inner
*Retinal pigmented epithelium (RPE): next to choroid 
*Photoreceptor layer - Rods and cones. 
External limiting membrane 
Outer nuclear layer 
Outer plexiform layer 
Inner nuclear layer 
Inner plexiform layer 
*Ganglion cell layer - axons form the optic nerve. 
Nerve fiber layer 
Internal limiting membrane: next to vitreous
*actually mentioned during lecture

Question 2

Recognize how light entering the eye stimulates the retina and results in phototransduction

Answer 2

light: cornea -> aqueous humor -> through lens-> vitreous humor -> retinal layers-> rods and cones->RPE-> optic nerve

Question 3

Know the function of the tapetum

Answer 3

Reflects scattered light back to retina; “second chance” to perceive light that has entered the eye

Question 4

Recognize the different retinal vascular patterns of domestic animals

Answer 4

cats- 3 vessels, stop right at edge of optic disc
dog- vessels cross over optic disc
horse- small vessels close to optic disc
alligator- no BV visible

Question 5

Understand how the optic nerve is formed and its function

Answer 5

formed by Retinal Ganglion Cells

sensory, carries visual info from retina to cortex

Question 6

lamina cribrosa

Answer 6

sieve-like area of the sclera.; axons from eye travel through with signals to the brain

Question 7

bipolar cells

Answer 7

exists between photoreceptors (rod cells and cone cells) and ganglion cells. They act, directly or indirectly, to transmit signals from the photoreceptors to the ganglion cells

Question 8

retrobulbar

Answer 8

space located behind the globe of the eye; inject a block when trying to examine a horses eye

Question 9

anagiotic

Answer 9

absence of any vasculature in the sensory retina

Question 10

amacrine cells

Answer 10

interneurons in the retina; responsible for 70% of input to retinal ganglion cells

Question 11

horizontal cells

Answer 11

laterally interconnecting neurons having cell bodies in the inner nuclear layer of the retina of vertebrate eyes. They help integrate and regulate the input from multiple photoreceptor cells. Among their functions, horizontal cells are responsible for allowing eyes to adjust to see well under both bright and dim light conditions.

Question 12

axon

Answer 12

composing optic nerve; part of ganglion cell layer

Question 13

retinal pigment epithelium

Answer 13

outer layer of the retina, last layer of retina light hits

Question 14

detachment

Answer 14

increase in space between the photoreceptor and RPE layer of the retina; causes changes in sight, partial to total blindness; can be surgically repaired to restore sight; can happen in older, kidney failure cats

Question 15

choroid

Answer 15

part of the uveal tunic, contains the tapetum (not present in all species); light bounces off it to give it a “second chance” at the retina

Question 16

optic disc

Answer 16

disc visible where the optic nerve sits at the back of the eye

Question 17

holoangiotic

Answer 17

sensory retina receives a direct blood supply

Question 18

merangiotic

Answer 18

blood vessels are localized to a region of the retina-lagomorphs

Question 19

paurangiotic

Answer 19

blood vessels in the retina are only near the optic disc

Question 20

signal transduction

Answer 20

retina processes light and converts the light signal into a neural signal

Question 21

Where do retinal detachments occur?

Answer 21

between photoreceptor and RPE.

Question 22

Visual pathway afferent arms:

Answer 22

Photoreceptors, C2 (Optic), Optic chiasm, optic tract, pretectal nucleus

Question 23

Visual pathway efferent arms:

Answer 23

Preganglionic fibers of C3 (Oculmotor), Parasym fibers of Oculomotor, Ciliary ganglion, short ciliary nerve, iris sphincter muscles