Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuroscience Week 2 > Retinal Phototransduction and Signal Processing > Flashcards

Retinal Phototransduction and Signal Processing Flashcards

1
Q

sclera

A
  • relatively spherical and avascular
  • white dense CT that covers the globe posterior to the cornea
  • strong tough external framework to protect the delicate optic and neural structures
  • maintains the shape of the globe so that the retinal image is undisturbed and provides attachment for the extraocular muscles to rotate the globe and the ciliary muscle to accommodate the lends
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

cornea

A
  • the window of the eye
  • mechanically strong and transparent CT that covers anterior 1/6 surface of the eye
  • most powerful focusing element of the eye, twice as powerful as the lens
  • 80% of the refraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

lens

A
  • specialized epithelial tissue that is responsible for fine tuning the image that is projected on the retina
  • inside the eye surrounded by aqueous humor
  • transparent, has high refractive power
  • elastin based zonular fibers stabilize the lens and allow accommodation to occur
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

uveal tract

A
  • consist s of three structures
  • choroid
  • ciliary body
  • iris
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

choroid

A

-capillary bed nourishing the photoreceptors and outer retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

ciliary body

A
  • two parts

- muscle controlling refractive power of the lens and vascular component that produces aq humor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

iris

A
  • colored portion of the eye seen through the cornea

- contains two sets of muscles with opposing actions that allow the size of the pupil to be adjusted by neural control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

anterior chamber

A
  • volume behind the cornea and in front of the lens

- filled with aq humor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

posterior chamber

A

-region between the vitreous and the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

vitreous humor

A

-thick gelatinous substance filling the space between the back of the lens and the surface of the retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

retina

A

-contains neurons that absorb light and process visual information in the images and send it to the brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

macula

A
  • oval spot containing a yellowish pigment

- supports high acuity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

fovea

A

-small depression at the center of the macula-highest spatial acuity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

optic disk

A
  • whitish circular area where retinal axons leave the eye and travel through the optic nerve to targets in the midbrain and thalamus
  • where blood vessels enter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

ophthalmic artery

A
  • anterior segment to iris and ciliary body

- retinal systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

vascular for anterior segment

A

from anterior ciliary arteries and long posterior ciliary arteries
-penetrating vessels through the sclera vascularize the iris and ciliary body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

cataracts

A
  • clouding of the lens that affects vision
  • related to aging
  • leading cause of blindness worldwide
  • by 80 more than half of americans have one or have had surgery
  • risk factors-aging, diabetes, sunlight, smoking
  • hazy vision, poor night vision, glare and faded colors
  • surgical removal of the cloudy lens and replacement with an artifical lens
  • aggregates of proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

glaucoma

A
  • group of diseases that damage the eye’s optic nerve and can result in vision loss
  • normal tension, open angle, closed angle
  • risks- elevated eye pressure, thin cornea, abnormal optic nerve anatomy, high blood pressure
  • not all ppl with high IOP develop glaucoma
  • no symptoms until too late, loss of peripheral visual fields
  • eye drops to increase aq production or increase drainage
  • surgery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

production and flow of aqeuous humor

A
  • circulating aq humor nourishes the cornea and lens structures that must be transparent and therefore devoid of blood vessels
    1. secreted by ciliary epithelium lining the ciliary processes
    2. flows around the lens and through the pupil into the anterior chamber
    3. leave the eye by passive flow at the anterior chamber angle
  • open angle slow development caused by obstruction of drainage canals
  • closed angle is sudden increase in IOP, closed or narrow angle between iris and cornea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

photoreceptors

A
  • point toward back of the eye
  • retina is window to brain
  • ganglion layer, inner retina, the photoreceptor nuclei and inner segments before PR outer segments, where phototransduction occurs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

layers of the retina

A

3 nuclear, 2 plexiform, 1 fiber

  • nerve fiber layer
  • ganglion cell layer
  • inner plexiform layer
  • inner nuclear layer
  • outer plexiform layer
  • outer nuclear layer
  • PR outer segments
  • pigment epithelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

outer nuclear layer

A

-photoreceptor somas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

outer plexiform layers

A

-photoreceptor/ bipolar/ horizontal cell synapses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

inner nuclear layer

A

-horizontal, bipolar, amacrine cell somas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

inner plexiform layer

A

-bipolar/amacrine/ganglion cell synapses

26
Q

ganglion cell layer

A

-ganglion cell somas

27
Q

pigmented epithelium

A
  • melanin containing cells behind PR
  • backstop for light
  • maintains phototransduction machinery of PR by recycling discs, pigment regeneration, and PR nourishment
28
Q

cell types in retina

A
  • PR
  • horizontals
  • bipolar
  • amacrine
  • ganglion
29
Q

glia in retina

A
  • muller glial cells
  • microglia (immune system)
  • astrocytes-neurovascular
30
Q

vertical information flow

A

-PR–>bipolar cells–>ganglion cells

31
Q

lateral information flow

A

-mediated by horizontal cells and amacrine cells

32
Q

neurotransmission

A
  • cells along vertical pathways release glutamate

- cells mediating lateral information transmission mostly GABA or glycineric

33
Q

rods and cones

A
  • ciliated cells
  • outer segment connected to inner via connecting cilium
  • outer segment has phototransduction machinery
  • inner is housekeeping
  • synaptic terminal connects bipolar and horizontal cells
  • nt is glutamate
34
Q

PR response to light 1

A
  • respond to light with graded hyperpolarizations
  • in darkness cells are depolarized and nt released continuously
  • when in light- respond with graded hyperpolarizations
  • spreads passively to the synapse where is reduces amount of glutamate
35
Q

PR in dark

A
  • Na and Ca cations flow inward through cGMP gated channels at the outer segment
  • K ions flow outward through K selective channels at the inner segments
  • Na and Ca in depolarizes the cell
  • K out hyperpolarlizes the cell
  • combined action result in resting potential of -40
36
Q

PR in light

A
  • absorption of light reduces cGMP levels in the outer segment
  • cGMP gated channels close, reducing the inflow of Na and Ca
  • K continues to flow out of the inner segment reducing the amount of positive charger
  • PR hyperpolarized and nt decreases
  • reduction of inward current results in a reduction of intracellular Ca
37
Q

phototransduction

A
  • rhodopsin is pigment opsin plus chromophore retinal in disk membranes (opsin is G protein coupled receptor)
  • retinal absorbs photon and rhodopsin becomes activated
  • goes from 11-cis to all trans and activates transducin and decreases cGMP, which increases hyperpol
  • all trans retinal breaks covalent bond and exits pocket
  • high amplification
  • 1 R* closes 200 cGMP channels
38
Q

dark adaptation

A
  • restoration of sensitivity after exposure to illumination
  • after retinol is used, it jumps out and is transferred to the pigment epithelium on IRBP and changed back into 11-cis to be put back in with an opsin molecule
39
Q

fovea

A
  • the ganglion cells, inner plexiform layer and inner nuclear layer are pushed away for high acuity
  • fovea has lots of cones, periphery has rods
40
Q

one bipolar cell, many rods

A
  • high sensitivity

- low resolution

41
Q

one bipolar cell, one cone

A
  • each cone projects onto 2 bipolar cells, but each bipolar cell only has one cone
  • low sensitivity, high resolution
  • midget BC
42
Q

functional specialization of rod and cone systems

A
  • rods in periphery, very sensitive, respond to single photon, high convergence onto bipolar cells, pool signals from 15-30 rods
  • high sens low spatial, most numerous
  • cones in fovea, less sensitive, need 100 photons to elicit response, high acuity, high spatial resolution, low sens, color
43
Q

scotropic

A 
rod only
-high sens
-low acuity
no color
-dark
44
Q

photopic

A
  • cone only
  • low sens, high acuity
  • color
45
Q

mesopic

A

cone and rod together

46
Q

retinitis pigmentosa

A
  • a group of genetic eye conditions that lead to incurable blindness 1:4000
  • night blindness, tunnel vision, legally blind by 40, loss of ERG
  • mutation of genes for rhodopsin and other rod proteins (PDE, cGMP gated channels, RDS/peripherin) leading to degeneration of rods and eventually cones
  • over 100 gene defecs
  • no treatment
47
Q

age related macular degeneration

A
  • leading cause of vision loss, 10% of people over 50, 33% of people over 75
  • wet- abnomal blood vessels behind the retina grow under the macula, leaking and rapidly damaging the retina
  • dry-RPE and PR of the macula degenerate, accumulation of drusen, 85%
  • loss of central vision and acuity
  • disease encroaches on freedom of elderly and mobility
  • risk- aging, smoking, inheritence
  • local IF and complement
  • treatment- wet- laser coag of vessels and intravitreal injection of anti-neovascular agents
  • dry- gradual atrophy of central retina, antioxidants slow
48
Q

diabetic retinopathy

A
  • retinopathy from complications of DM
  • risk- up to 80% of all patients who have had diabetes for 10 years or more
  • no early warning signs
  • blurry vision with macular edema
  • new vessels bleed into retina and block vision
  • non proliferative-hyperglycemia induced pericyte death leads to incompetence of the vascular walls, micro aneurysms and dot and blot hemorrhages
  • vascular beading and cotton wool spots
  • proliferative stage-new, fragile vessels grow, which leak blood
  • laser surgery to reduce edema and injections with anti-neovascular factors
49
Q

spatial contrast

A

-visual system is good at differentiating light/dark

50
Q

receptive field

A
  • area of the retina that when stimulated elicits a change in the response of a neuron
  • on center and off center
51
Q

on center/off surround receptive field

A
  • light in center- excitation (depol)
  • light in surround- inhibition (hyperpol)
  • an optimal excitatory stimulus is a spot of light against a dark background
  • an optimal inhibitory stimulus is a dark spot against a light background
  • APs increase when light in center, decrease when in surround
52
Q

off center/ on surround

A
  • light in center- inhibition (hyperpol)
  • light in surround- excitation (depol)
  • optimal excitatory- dark spot against light
  • optimal inhibitory- light spot against dark
53
Q

on center moving from dark to light

A

-first goes down because more inhibitory, then increases when center in light, then back down

54
Q

on/off ganglion and bipolar cells

A
  • on BCs depolarize in response to light, hyperpolarize in dark, off hyperpol in response to light, depol in dark
  • glutamate receptors on bipolar cells determine the on off center properties of the BCs and those of the ganglion cells they innervate
  • graded depolarizations of BCs lead to increased glutamate release at their synapses and depolarization of the GC they contact
  • if cone hyperpolarizes (response to light), off center bipolar cell gets same sign signal and hyperpolarizes, then off center ganglion doesn’t fire AP
  • if cone hyperpolarizes, on center bipolar cell gets opposite sign signal and BC depolarizes, ganglion cell fires APs
55
Q

receptive field construction

A
  • horizontal cells are post-synaptic to photoreceptors
  • if cone hyperpolarizes, horizontal cells get signal and send opposite back
  • graded potentials
  • lateral inhibition to bipolar cells
  • OPL by horizontal cells, in IPL by amacrine
  • horizontal cells form the surround
  • see slide
56
Q

color

A

-short, medium, long wavelength cones are basis for color (blue, green, red)

57
Q

cone opsins

A
  • G protein coupled receptor superfamily of signal transducing receptors
  • 7 transmembrane domains
  • tunes absorption of light to a particular region of the spectrum
  • color opsins defined by different proteins
58
Q

color blindness

A

-absence of one or more cone classes are responsible for common color blindness

59
Q

anatomical parallel pathways

A
  • M cells and P cells different kinds of cones for different types of light
  • parvocellular and magnocellular
  • koniocellular pathway
  • P cells red/green off on, M blue/yellow
60
Q

intrinsically photosensitive retinal ganglion cells

A
  • contain primitive opsin
  • autonomous response to bright lights
  • vast dendritic trees
  • pupillary control
  • other roles include synchronization of circadian rhythms

Neuroscience Week 2 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions