Vision

Question 1

What is comprised of the fibrous tunic?

Answer 1

cornea
sclera

Question 2

What is part of the vascular part of the eye? “uvea”

Answer 2

choroid
ciliary body
iris

Question 3

What is the nervous tunic of the eye called?

Answer 3

retina

Question 4

What is the blind spot of the eye called?

Answer 4

optic disc

Question 5

What is the densest part of the retina?

Answer 5

fovea centralis

Question 6

What 2 things comprises the retina?

Answer 6

optic disc
horizontal visual streak

Question 7

Light is _____ as it passes through the cornea and lens

Answer 7

refracted

Question 8

The [cornea/retina] refracts more light than the lens

Answer 8

cornea

Question 9

What fine-tunes the image?

Answer 9

lens

Question 10

When the lens becomes [rounder/thinner], it increases refraction for near vision

Answer 10

rounder

Question 11

What is the accommodation of the lens?

Answer 11

refracting more or less in the lens to see near of far

Question 12

When the lens becomes [rounder/thinner], it increases refraction for distance vision

Answer 12

thinner

Question 13

List the layers of the retina from superficial to deep

Answer 13

pigment cell layer
photoreceptor layer
outer nuclear layer
outer plexiform layer
inner nuclear layer
inner plexiform layer
ganglion cell layer
optic nerve layer

Question 14

What is the pigment cell layer of the retina?

Answer 14

absorbs light
prevents light from scattering between photoreceptors
convert TRANS-retinal to CIS-retinal needed by photoreceptors

Question 15

What is the photoreceptor layer?

Answer 15

outer portion of rods and cones that contain light-sensitive components

Question 16

What is the outer nuclear layer?

Answer 16

cell bodies and nuclei of rods and cones

Question 17

What is the outer plexiform layer?

Answer 17

synapses of photoreceptor cell axon terminals with dendrites of retinal interneurons (bipolar and horizontal cells)

Question 18

What is the inner nuclear layer?

Answer 18

cell bodies of retinal interneurons
- Bipolar cells (B)
- Horizontal cells (H)
- Amacrine cells (A)

Question 19

What is the inner plexiform layer?

Answer 19

synapses of retinal interneuron axon terminals with dendrites of ganglion cells

Question 20

What are the output cells of the retina?

Answer 20

ganglion (G) cells

Question 21

What is the ganglion cell layer?

Answer 21

cell bodies of ganglion cells
output cells of the retina

Question 22

What is the optic nerve layer?

Answer 22

axons of ganglion cells traversing the inner retina on their way to the optic disc —> optic nerve

Question 23

Where is the tapetum lucidum found?

Answer 23

choroid

Question 24

What is the tapetum lucidum?

Answer 24

reflective layer in the choroid that increases light detection in dark conditions

Question 25

T/F: Retinal pigment epithelium lacks melanin overlying tapetum

Answer 25

true - allows light to pass through and reflect back to stimulate photoreceptors may decrease acuity

Question 26

[Rods/Cones] are used in scotopic vision.

Answer 26

rods

Question 27

What do the outer segment of rods contain?

Answer 27

contains photopigments specialized to absorb light

Question 28

What is rhodopsin? It has a [high/low] threshold

Answer 28

absorbs light low

Question 29

What does rhodopsin contain in combination with opsin, a G-protein coupled receptor?

Answer 29

retinal (vitamin A derivative)

Question 30

What does the outer segment of cone cells do?

Answer 30

tapers

Question 31

Cones have ______ and _____ which have a higher threshold.

Answer 31

photopsins lodopsins

Question 32

Many domestic animals have ____ types of cones, which are composed of ______ in combination with a different type of opsin.

Answer 32

2 retinal

Question 33

What is phototransduction?

Answer 33

light converted to electric signal cis —> trans, changes shape of G-protein PDE degrades cGMP cGMP gated Na+ channels close hyper polarize the cell and decrease glutamate release

Question 34

In the dark, rhodopsin contains [cis/trans]-retinal, but with light absorption, it causes transformation to [cis/trans]-retinal which dissociates from opsin aka a "________"

Answer 34

cis trans bleaching reaction

Question 35

After bleaching ____ must be rebuilt for the rod to function

Answer 35

rhodopsin

Question 36

T/F: Rods function well in bright light

Answer 36

FALSE

Question 37

What is the first order neuron for the retinal pathway?

Answer 37

bipolar cell

Question 38

List the interneurons of the retinal pathway

Answer 38

bipolar cell amacrine cell horizontal cell processing

Question 39

List the 2nd order neuron

Answer 39

ganglion cells

Question 40

_____ work best in dim light/dark conditions

Answer 40

Rods

Question 41

Many _____ converge on one bipolar cell

Answer 41

rods

Question 42

What is MORE likely to be activated by low levels of light due to convergence of rods

Answer 42

bipolar cells

Question 43

What is the 3rd order neuron for the pathway for conscious perception of vision?

Answer 43

lateral geniculate nucleus in thalamus "sub-cortical"

Question 44

Where do axons for the LGN go?

Answer 44

visual cortex in occipital lon visual association areas parietal and temporal lobes

Question 45

Each visual field represented in the [ipsilateral/contralateral] optic tract

Answer 45

contralateral

Question 46

The closer together the eyes are, the [more/less] input each eye gets from BOTH visual fields

Answer 46

more

Question 47

Horses have [more/less] decussation which allows for a greater field of vision

Answer 47

more

Question 48

Increased medial eye placement —> increased binocular vision overlap —> [increased/decreased] decussation at optic chiasm

Answer 48

decreased

Question 49

T/F: Visual input that crosses the midline before entering the eye does NOT need to cross the midline again

Answer 49

TRUE

Question 50

What is the pupillary light response? What percentage of fibers of to the midbrain protextal nucleus and so on?

Answer 50

moves to rostral colliculus —> accessory oculomotor nucleus —> ciliary ganglion —> pupillary sphincter (parasympathetic) BYPASSES the LGN 20%

Question 51

PLR is a ______ reflex inducing [sympathetic/parasympathetic]-induced pupil constriction

Answer 51

subcortical (midbrain) parasympathetic

Question 52

Does having a pupillary light response mean you have conscious perception of vision?

Answer 52

NO - you could be blind in one eye and still have a pupillary light response

Question 53

What is anisocoria?

Answer 53

having different sized pupils

Question 54

Trace the menace response pathway

Answer 54

retina —> optic nerve —> optic disc —> optic tract —> visual cortex (lateral geniculus and rostral colliculus) —> facial motor nucleus —> facial n. in medulla —> auriculopalpebral n.

Question 55

What does subcortical mean?

Answer 55

midbrain doesn't go all the way to the cortex

Question 56

What does cortical mean?

Answer 56

goes all the way to the cortex

Question 57

The menace response is a [cortical/subcortical] response pathway

Answer 57

cortical

Question 58

What is the vestibulo-ocular reflex?

Answer 58

initiates compensating eye movement to keep vision fixed when head turns

Question 59

What nerves are involved in the vestibulo-ocular reflex?

Answer 59

CN 3, 4, 6

Question 60

Where is the vestibulo-ocular reflex found?

Answer 60

medial longitudinal fasciculus

Question 61

What is the visual startle reflex?

Answer 61

rostral colliculus (tectum) in midbrain decussates descends cord in tectospinal tract contraction of neck muscles to turn toward stimulus