(40) The Visual System Flashcards Preview

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Flashcards in (40) The Visual System Deck (44):
1

What part of the brain in responsible for visual perception?

occipital cortex

2

What part of the brain in responsible for visual memory?

parietal an temporal

3

What part of the brain in responsible for visual reflexes?

brainstem and spinal cord

4

What part of the brain in responsible for circadian rhythm

pineal gland and dienchephalon

5

what focuses the incoming light from objects we see to create a crisp image

fovea

6

What happens to the light from an object after it enters our eye to get to the retina?

refracted by cornea
inverted through pupil
refracted by lens
projected onto fovea
fovea focuses/fine tunes light
light hits retina

7

how is the image of the object we are seeing oriented on the fovea in our eye?

inverted and smaller

*due to refraction by cornea and lens

8

What muscle controls lens refraction and how it is innervated

cilliary muscle via sympathetic and parasympathetic control

9

protective later to the retinal and choroid

sclers

10

choroid provides blood flow and nutrients to....

photoreceptors and RPE cells = OUTER retina

11

describe the circulation in the fovea

there is NONE = no blood vessels bc blood distorts the image

12

describe the cellular organization of the retina

photoreceptor cell bodies lie in outer nuclear layer and project to outer flexiform layer where they synapse with bipolar cells who's cell bodies are found in the inner nuclear layer. these bipolar cells project to ganglion cells in the ganglion layer. the ganglion cell projections coalesce to form the optic N

13

provides the barrier between the retina and the choroid

retinal pigmented cells

14

support the photoreceptor by providing nutrients

RPE

15

What are the interneurons that lie in the retina and what cells do they synapse with and what is their function?

horizontal (outer plexiform layer) --modulate photoreceptors and bipolar cells
amacrines (inner plexiform layer) --modulate bipolar cells

16

what form the blind spot?

optic N entry into retina

17

how are the retinal cells arranged in the fovea?

radially to minimizes distortion of the image

18

Macular degeneration results when blood vessels damage the ____ and break through to grow into the ___ region of the eye

RPE and macular region

19

2 main functions of the RPE

1. provide barrier between retina and choroid
2. eat outer rod segments every 10 days (prevents macular degeneration/drusen production)

20

function of rods

produces black and white vision

21

what is the spherule?

synapse of rods with bipolar cells and horizontal interneurons

22

which cones are carried on X chromosome

M and L

23

what is the purpose of the photoreceptors

abs photons and convert it into electrical signal

24

what is the response that rods and cones have to light

hyperpolarize
**only sensory cells that hyperpolarize in response to a signal, all others depolarize

25

describe the bichem that is going on in a photoreceptor that allows for a photon to be converted into an electrical signal

light converts cis retinal to trans retinal which activates rod opsin-rhodopsin which converts GDP to GTP which activates PDE. active PDC lowers cGMP levels which closes the cGMP-gated ion channel (Ca and Na). no cations coming in = hyperpolarization = electrical signal that is the visual response

26

how is the hyperpolarized state of the photoreceptor reversed?

decreased Ca levels activate guanyl cyclase and inhibits PDE which increases cGMP and allows the cations (Ca and Na) channels to reopen

27

how is the trans retinal converted back to cis retinal so that another photon can activate it

active rhodopsin-GTP is dephosphorylated back to GDP and allows all the trans to go back to cis
**rhodopsin kinase P-rhodompsin which binds arrestin to make the moleucle inactive untl the photon shows up

28

At the bipolar ganglion cell synapse, ______ cells detect major changes in activity levels

amacrine

29

cones and rods have thier own bipolar cells. which ones are found in the periphery and which ones are centrally?

periph = rods

cones = central

30

what cells help converve the signals from multiple rod photoreceptors to fewer rob bipolar cells? (i.e. convergence)

horizontal cells

31

what ganglion cells are found in the periphery and receive most of their input from rods

alpha-ganglion cells

32

alpha ganglion cells project to _____ and function to....

magnocellular layer of lateral geniculate nucleus and function to determine the location of object in space

33

what ganglion cells are found in the central retianl and receive most of their input from cones

beta ganglion cells

34

beta ganglion cells project to _____ and function to....

parvocellular region in lateral geniculate nucleus to define color and texture

35

the foves has (rods, cones, or both)

cones

36

what ganglion cells decussate in the optic chiasm

only nasal fibers

37

left visual field is processed by what side of the cortex

right

38

M pathway originates in the ______ cells and projects to lateral geniculate layers _____ then to layer ____ in the cortex. This pathway relays ____ info

originates in magnocellular ganglion cells
layer 1-2 in LGN
4C-alpha in cortex

space information

39

P pathway originates in the ______ cells and projects to lateral geniculate layers _____ then to layer ____ in the cortex. This pathway relays ____ info

originates in parvocellular ganglion cells
layer 3-6 in LGN
4C-beta in cortex

form information

40

high glc causes damage to what cells in the eye

retinal epiptheral cells and pericytes and neurons

**damage activates growth facotrs

41

what vasculature is damaged in diabetic retinopathy vs macular degeneration

DR = retinal
AMD = choroid

42

how is vision field loss compared in DR and AMD

DR = central
AMD = all vision

43

how is dry AMD different than wet AMD

Dry more common than wet

dry has less vision loss and is usually unilateral while wet is bilateral

dry has drusen and wet sometimes foes

44

What are the treatments for AMD

Avastin and Macugen injections that block vasculature growth **they halt progression and do not reverse***