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Block 5 > neuro - week 2 > Flashcards

neuro - week 2 Flashcards

0
Q

Where is the fovea located relative to the Optic Nerve?

A

nasally

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1
Q

Posteriorly, what are the layers of the eye? (3)

A

Outside to in: Sclera –> Choroid –> Retina

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2
Q

What is peripapillary?

A

near or around the nerve head in the eye

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3
Q

What is papilledema?

A

swollen nerve head in the eye

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4
Q

What structure drives the refractory power of the eye?

A

Cornea

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5
Q

What are the layers of the cornea? (5)

A

Epithelium –> Bowman’s membrane –> Stroma –> Descemet’s membrane –> Endothelium

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6
Q

What are the functions of the cornea? (2)

A

1) major refractive structure (50 D)

2) Protects eye from environment

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7
Q

What are the characteristics of the Epithelium of the cornea?

Types of cells?
characteristic?

A

Types of cells: stratified squamous cells

Characteristic: high regenerative capacity/heals quickly

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8
Q

What are the characteristics of Bowman’s membrane?

What is it made of?
Function/characteristics? (2)

A

Made of: acelleular layer of unorganized collagen fibers

function: barrier to infection
characteristic: can heal, but scars can form

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9
Q

What is the stroma?

Made of?
Function? (2)

A

Made of: organized type 1 collagen bundles

Function:

1) binds water to maintain corneal clarity
2) contributes to variation in corneal thickness

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10
Q

What is Descemet’s membrane?

Description?
function? (2)

A

Description: The basement membrane of the endothelium of the cornea

Function:

1) helps keep the stroma clear
2) Increases thickness with age

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11
Q

What is the Endolthelium of the cornea?

Cell type?
Function?

A

Cell type: simple squamous epithelia

function: pumps water out of stroma

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12
Q

What is Myopia?

Name?

location of focal point?

A

Name: nearsightedness

Location of focal point: anterior to retina

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13
Q

What is Hyperopia?

Name?
Location of focal point?

A

Name: farsightedness

location of focal point: posterior to retina

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14
Q

Why is vision more clear when pupil is small?

A

A small pupil limits the point spread function and wave aberrations of your eye.

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15
Q

What are the three parts of the Uvea?

A

1) Choroid
2) Ciliary body
3) Iris

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16
Q

What are the layers of the choroid? (3)

A

Out to in:

Vessel layer –> Choriocapillary layre –> Bruch’s membrane

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17
Q

Why does the choroid have melinin?

A

Regulates light coming into the eye by absorbing light that doesn’t go through the pupil.

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18
Q

Which areas does the Ciliary body contact? (3)

A

1) Vitreous body
2) sclera
3) posterior chamber

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19
Q

What is the function of ciliary processes?

A

Increases surface area to secret the aqueous humor

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20
Q

What is the limbus of the eye?

A

Where the nearly opaque sclera transitions to transparent cornea

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21
Q

What is the Trabecular meshwork?

Location?
Function?

A

Location: within ciliary body near the LIMBUS

Function: aqueous humor is drained from anterior chamber via the trabecular meshwork

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22
Q

What is the main function of the Iris?

A

to regulate the amount of light entering the eye

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23
Q

What are the parts of the iris? (4)

A

1) anterior aspect
2) posterior surface
3) dilator pupillae muscle
4) sphincter pupillae muscle

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24
Q

What are the characteristics of the anterior aspect of the Iris?

Made of?
Function? (2)

A

Made of: vascular, loose CT with interspersed melanoctyes

Function:

1) melanocytes absorb light that doesn’t go through the pupil (you want to restrict light to go only through pupil)
2) melanocytes also determine eye color

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25
Q

What are the characteristics of the Posterior surface of the Iris?

Made of?
Function?

A

Made of: double layer of pigmented epithelium

Function: absorbs light

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26
Q

What are the characteristics of the dilator pupillae?

Cell organization?
Function?
Innervation?

A

Cell organization: radially arranged myoepithelial cells

Function: Contraction leads to dilation of eye

Innervation: sympathetic

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27
Q

What are the characteristics of the sphincter pupillae muscle?

Organization?
Function?
Innervation?

A

Organization: concentric smooth muscle bundles at the pupil margin

Function: contraction constricts the eye

Innervation: parasympathetic

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28
Q

What is heterochromia?

Where does it manifest?

Why is it important?

A

Heterochromia is having multiple colors in the same iris.

Manifests in the anterior aspect of the Iris

Could be a sign for pathology unless it was there since birth

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29
Q

Where is the anterior chamber of the eye?

A

Between the lens and cornea

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30
Q

What is the purpose of the anterior chamber? What does it contain?

A

Purpose: involved in maintaing intraocular pressure

Contains aqueous humor and is avascular

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31
Q

Where is the posterior chamber?

A

In between the Ciliary body and Lens, Posterior to the Iris

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32
Q

What is the pathway of aqueous humor flow?

A

From ciliary processes –> posterior chamber –> anterior chamber –> trabecular meshwork –> Schlemm’s canal –> veins of sclera

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33
Q

What are the types of glaucoma?

A

1) open angle

2) angle closure

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34
Q

What is Open Angle glaucoma? Why is it called that?

A

The trabecular meshwork is not absorbing aqueous humor well so pressure builds up.

It’s called Open angle because there is a nice path for the aqueous flow to go from posterior to anterior chamber

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35
Q

What is Angle closure glaucoma? Why is it called that?

A

The Iris is butted up against the trabecular meshwork, therby closing that angle and not allowing aqueous humor to flow from the posterior chamber

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36
Q

When would it be dangerous to dilate a patients eye?

A

If they have Angle closure glaucoma

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37
Q

What are clinical signs of Glaucoma?

A

1) elevated Pressure

2) visual field defects starting in the PERIPHERY

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38
Q

What is Lamina Cribrosa?

A

Network of collagen fibers through which fibers of the optic nerve exit the eye

May be altered in glaucoma

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39
Q

What are the structural components of the lens? (3)

A

1) Capsule: ECM surrounding lens
2) Epithelium: anterior surface
3) Lens fibers: body of lens with no organelles

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40
Q

What are the functions of the Lens? (2)

A

1) second to cornea in refractive power

2) accommodation

41
Q

How does the lens change shape in accommodation? (thickness, focus, ciliary muscles, zonule fibers)

A

Thinner = focused on distant objects = relaxed ciliary muscles = tight zonule fibers

Thicker = focused on near objects = constricted ciliary muscles = loose zonule fibers

42
Q

What are cataracts? How are the types? (3)

A

Clouding of the lens

1) nuclear cataract: located in the center of the lens
2) cortical cataracts: layer surrounding nucleus
3) posterior capsular cataract: found in the back outer layer of lens

43
Q

Which cataract develops most rapidly?

A

posterior capsular cataract

44
Q

What is the Vitreous body?

made of? (2)
function? (2)

A

Made of: acellular - major macromolecules are type 2 collagen and hyaluronic acid

Function:

1) transparent
2) nutritive function

45
Q

What are the layers of the Retina?

A

Ganglion –>Inner plexiform –> Inner nuclear –> Outer Plexiform –> Outer Nuclear –> rods/cons –> pigment epithelium –> choroid –> sclera

(choroid and sclera not part of retina)

46
Q

What is the inner limiting membrane (ILN)?

A

The ILN separates the retina from the virtuous humor

47
Q

How can you tell what part of the retina is being imaged?

At fovea?
Central near fovea?
Peripheral?

A

At fovea: Ganglion cells, Inner plexiform and inner nuclear layer will be absent

Central near fovea? all layers present and ganglion layer thickest

Peripheral? all layers present but ganglion layer is thinner the further away from fovea

48
Q

What are the layers of photoreceptors? (3)

A

Inner segment –> connecting cilium –> Outer segment

49
Q

What is the function of the inner segment of photoreceptors?

A

protein synthesis and energy production

50
Q

What is the function of the connecting cilium of photoreceptors?

A

transport of proteins (10 billian opsin molecules per second)

51
Q

What is the function of the Outer segment?

A

Flattened membrane discs with photosensitive visual pigments (opsin)

52
Q

What is the difference between the structures of Rods and Cones?

A

Rods: long slender outer segment
Cones: conical outer segment with discs

53
Q

What are the structural characteristics of the foveal? (3)

A

1) No inner layers (ganglion cells, inner plexiform and nuclear layer)
2) Lots of cons and no rods
3) avascular

54
Q

How does the size of cons change as you move away from fovea?

A

inner segments of cones get bigger

55
Q

What are the functions of the Retinal Pigment Epithelium (RPE)? (6)

A

1) absorbs scattered light (melanin)
2) transports nutrients and ions between photoreceptors and choriocoapillaris
3) spatial buffering of ions
4) reisomerization of all-trans retinal
5) outer segment renewal
6) secretion of growth factors

56
Q

What is the ratio of photoreceptors to RPE cell?

A

40 photoreceptors to 1 RPE cell

57
Q

How are photoreceptors renewed? When is peak activity for cones? When is peak activity for rods?

A

an RPE cell engulfs and digests 10% of the mass of each outer segement per day

Peak activity for cone shedding: dusk
Peak activity for rod shedding: dawn

58
Q

What is age related macular degeneration? (AMD)

Cause?
Type of vision loss?
“dry” vs “wet” version?

A

Cause: Drusen develop within Bruch’s membrane as you age

Vision loss: Vision loss is slow, central vision deteriorates first

“wet” version: Drusen cause a break in bruch’s membrane or RPE and you get neovascularization from the choroid

59
Q

What two branches of the opthalmic artery supply the eye? What parts of the eye do each supply?

A

Retinal artery system (30%): supplies inner retina

Ciliary artery system (70%): choroid

60
Q

What is Albinism?

Oculocutaneous albinism? (OCA)
Ocular albinism? (OA)
Symptoms?

A

OCA: no pigment anywhere
OA: no pigment in eye, normal skin and hair

Symptoms: universal visual problems and foveal hypoplasia

61
Q

What is foveal hypoplasia?

A

arrested development of the fovea, occurs in albinism

62
Q

What is the ratio of Rods to cones?

A

20 rods for every cone

63
Q

What are the following characteristics of Rods?

Sensitivity?
speed/integration time?
spatial resolution?
pigmentation? 
directionally selective?
A 
Sensitivity: more sensitive
speed: slow (integration time = 100 msec)
spatial resolution: poor
pigmentation: more
directionally selective: no
64
Q

What are the following characteristics of Cones?

Sensitivity?
speed/integration time?
spatial resolution?
pigmentation? 
directionally selective?
A 
Sensitivity: less sensitive
speed: fast (integration time: 25 msec)
spatial resolution: high
pigmentation: less
directionally selective: yes
65
Q

Which photoreceptors can saturate?

A

Only rods, cons can not saturate

66
Q

How do photoreceptors respond to light?

A

hyperpolorize

67
Q

What are photopigments made up of? (2)

A

1) chromophore (11-cis retinal)

2) opsin (protein component)

68
Q

What wavelength does chromophore normally aborbe?

A

375 nm

69
Q

What is the purpose of opsin?

A

Opsin “red shifts” the absorption spectrum of chromophore

70
Q

What are the three types of cones?

A

small - blue
medium - green
large - red

71
Q

What type of light do rods absorbe optimally?

A

blue-green

72
Q

Which type of cone receptor is their the least of?

A

small - blue

73
Q

What is the principle of univariance?

A

Photoreceptors are unable to disambiguate different wavelengths. “the output depends on quantum catch, but not upon which quanta are caught”

74
Q

What are the steps in phototransduction?

A

1) a photon isomerizes chromophore (11-cis to all trans) and releases opsin
2) opsin activates transducin
3) transducin activates PDE6 (phosphodiesterase type 6)
4) PDE converts cGMP to GMP
5) low cGMP closes ion channels
6) cone hyperpolorizes

75
Q

How do you convert all-trans retinal back to 11-cis retinal so to be able to respond to another photon?

A

all-trans retinal is shuttled to the RPE by inter-photoreceptor retinol binding protein (IRBP) where it is converted to 11-cis and shuttled back

76
Q

What is the role of inter-photoreceptor retinol binding protein (IRBP)?

A

Shuttles all-trans retinol and 11-cis retinol between RPE and photoreceptors

77
Q

Which type of photoreceptor degenerate first in retinal diseases and why?

A

Cones have a back up way of getting 11-cis retinal (muller glia cells supply it) so they can survive for longer

78
Q

Which type of phosphodiesterase are in the retinal cells?

A

PED5

79
Q

What type of cone is most likely to be disrupted by PDE inhibitors?

A

the blue (small) cones because their are much fewer of them

80
Q

What does it mean that photoreceptors are “OFF Centered cells”?

A

Photoreceptors respond to a photon by hyperpolorizing and releasing less neurotransmitter.

81
Q

What type of cells are bipolar cells? (2 types)

A

1) Off-center cell: stimulus in the center of its receptive field causes cell to hyperpolorizes and reduces the cells release of NT (sign conserving synapse)
2) On-center cells: stimulus in the center of its receptive field causes cell to depolarize and release more NT (sign reversing synapse)

82
Q

What types of synapses do “On-centered” bipolar cells have with the cones?

sign?
type of contact?
type of glutamate receptor?
response to glutamate?

A

sign: sign reversing
type of contact: invaginating contacts on to cones
glutamate receptor: metabatropic receptor
response to glutamate: hyperpolorizes

83
Q

What types of synapses do “Off-centered” bipolar cells have with the cones?

sign?
type of contact?
type of glutamate receptor?
response to glutamate?

A

sign: sign conserving
type of contact: flat/basal contact on to cones
Type of receptor: ionotropic receptor
response to glutamate: depolorizes

84
Q

What is the purpose of parallel pathways?

A

Improved sensitivity.

85
Q

What type of response do the following cells have (graded release of NT or action potential?)

Photoreceptors?
Bi-polar cells?
Ganglion cells?

A

Photoreceptors: graded release of NT
Bi-polar cells: graded release of NT
Ganglion cells: action potential

86
Q

What are the various types of ganglion cells and types of sign? (2)

A

1) on-center (sign conserving)

2) off-center (sign conserving)

87
Q

What types of anatomical types of ganglion cells are there? (2)

A

Parasol and Midget

88
Q

What are the characteristics of Parasol ganglion cells?

Size?
Receptive field?
projection?
type of response?

A

Size: Large
Receptive field: large
projection: magno layers
type of response: more transient

89
Q

What are the characteristics of Midget ganglion cells?

Size?
Receptive field?
projection?
type of response?

A

Size: small
Receptive field: small
Projection: parvo layers
type of response: more sustained

90
Q

What percentage of ganglion cells are Parasol and Midget?

A

Parasol: 10%
Midget: 90%

91
Q

What are photosensitive melanopsin RGC?

Description?
Purpose?
receptive fields?

A

Description: These ganglion cells have their own melanopsin so they can respond to light without the help of photorecpetors.

Purpose: responds to ambient light, believed to have a role in sleep/wake cycles

receptive fields: large

92
Q

What are horizontal cells?

A

laterally interconnects all the photoreceptors and causes lateral inhibition

93
Q

What neurotransimter do horizontal cells release?

A

GABA

94
Q

What is the purpose of lateral inhibition?

A

Improved resolution by enhancing edges

95
Q

What is rhodopsin?

A

The protein component of the rod photopigment

96
Q

What is Retinitis Pigmentosa (RP)?

Cause?
Symptoms?

A

Cause: mutation in Rhodopsin (does not tolerate polymorphisms)

Symptoms: night blindess (rods affected first), periphery to center defects

97
Q

What is Usher’s syndrom?

A

Most common form of deaf-blindness.

Involves defects in proteins involved in the connecting cilium and sensory ciliary of the ear, which is why it causes both blindess and deafness

98
Q

What can cause color vision defecets?

A

one of the cone systems is missing

99
Q

What is achromatopsia?

A

lacks cone function so they can’t see color. Caused by a mutation in cyclic nucleotide gated channel for the cones, so they can’t respond.

patients get photophobic because their rods are saturated

100
Q

What are some characteristics of congenital color vision defects?

Level of severity?
eyes affected?
visual acuity?
incidence?

A

Severity: same throughout life
eyes affected: both eyes affected equally
visual acuity: often unaffected
incidence: higher in males

101
Q

What are some characteristics of acquired color vision defects?

Level of severity?
eyes affected?
visual acuity?
incidence?

A

Severity: type and severity fluctuates
eyes affected: monocular differences often occur
Visual acuity: often reduced
incidence: equal in males and females

Block 5 (23 decks)

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