Brainscape's Knowledge GenomeTM

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


See full index

TORIC > Optic Nerve Physiology > Flashcards

Optic Nerve Physiology Flashcards

1
Q

Combien de retinal ganglion cells (RGC) sur la rétine?

A

Approximativement 1-1,2 million RGC in each retina.
One axon per cell projects into ON

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

Combien de retinal ganglion cells (RBC) perd-on avec l’âge?

A

Gradual loss during aging : 5000/year

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

Où se situe la lower rate of loss de retinal ganglion cells (RBC) sur la rétine

A

Rate of loss is lower for macular RGC

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

Que se produit-il avec les RGC dans le glaucome avancé?

A

In very advanced glaucoma, most RGC are already lost
Yearly age-related decline can lead to field loss even with good IOP control

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

Quel est le NT impliqué dans les RGC?

A

Glutamate

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

Épaisseur de la RGC layer a/n de la périphérie versus macula versus fovéa?

A

Périphérie : 10-20 um thick with single row of cells

Macula : 60-80 um thick with rows of cells

Fovéa : No ganglion cells

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

Quand l’OCT mac est-il pertinent dans le glaucome?

A

Macula usually has RGC remaining in ADVANCED glaucoma

Macular OCT may become more beneficial for advanced disease

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

Qu’est-ce que le RNFL?

A

Thicknest near disc
Axons range from 0,6-2,0 um in diameter
Axons form bundles in RNFL

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

Par quelles ¢ sont entourées les axones dans le RNFL?

A

Glial cells : Muller cells and astrocytes

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

Les axones du RNFL sont-ils ou non myélinisés?

A

Usually unmyelinated
(Possibilité que certains pts aient des axones myélinisés, mais aucune importante clinique)

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

Quels sont les cellules du NO?

A

Axons (cell bodies in RGC layer of retina)
Oligodendrocytes (and myelin)
Astrocytes
Microglia
Meninges

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

Combien d’axones y a t il dans le NO?

A

Environ 1 million in ON
Cell bodies in retina (RGC) so ON is pure white matter
Fascicles of 50-300 axons surrounded by septa (pia matter)

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

Quel est le rôle des oligodendrocytes?

A

20-30 processes per oligodendrocyte, each myelinating part of an axon
Myelin - Fatty, multilayered, insulating structure
Speeds conduction of impulse

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

Quel est le rôle des astrocytes?

A

Major supporting cell
Energy source for axon
Ionic homeostasis
Absorb glutamate
Prelaminar : glial tubes for axons
Lamilar : form collagen/elastin beams
First cells that respond to damage : affects support of axons, affects lamina cribs physiology, affects axoplasmic flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Quel est le rôle des microglia?

A

Resident macrophages of optic nerve/CNS

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

Quels sont les 3 méninges et leur rôle?

A

Dura:
- Thick fibrovascular tissue
- Continuous with sclera, periorbita, dural layer of brain

Arachnoid
- Middle layer
- Loose, thin, fibrovascular

Pia :
- Very thin vascular layer
- Forms septa between fascicles
- Blood supply to infraorbital and intracranial nerve

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

Quel espace entre les méninges est en continuité avec le NO et le cerveau?

A

Subdural space of ON is NOT continuous with subdural space of the brain

SUBARACHNOID space of ON is CONTINUOUS with rest of CNS

18
Q

Clinical correlation with the fact that subarachnoid space of ON is continuous with rest of CNS (aka 1 signe clinique).

A

Papilloedème
Increased intracranial presses transmitted around ON
Axoplasmic flow impeded distal to LC : swelling of disc head

19
Q

Dimensions de l’Optic Disc

A

Vertical : 1,9 mm (1,0-3,0 mm)
Horizontal : 1,7 mm (0,9-2,6 mm)
Disc area : 2,7 mm^2 (0,8-5,5 mm^2)
Neuroretinal rim area : 2,0 mm^2 (0,8-4,7 mm^2)

20
Q

Does OCT includes disc parameters?

A

Yes
OCT often includes disc parameters
Knowing averages can be helpful in noting outliers

21
Q

Quel est l’impact des fibres non myélinisées sur les dimensions du NO?

A

At disc, nerve is unmyelinated
Axons leave globe through lamina cribosa
Posterior to disc, diameter doubles dues to myelination

22
Q

Quel est le blood supply de la rétine, du NO, du infraorbital and optic canal ?

A

Retina :
- RGC layer and RNFL : retinal vascular circulation (central retinal artery)

ONH :
- Mostly Posterior Ciliary Arteries : comes from ophthalmic artery, branches form circle of Zinn-Haller
- Also central retinal artery
- Vessels to optic nerve are NOT fenestrated, can autoregulate

Intraorbital and optic canal :
- Pial circulation : direct from ophthalmic artery, central retinal artery, short posterior ciliary arteries

23
Q

Peut-on opérer un méningiome du NO?

A

Non. Meningiomas of ON often inoperable because removal would remove/disrupt pia.
Pia = importante pour la vascularisation du NO.

24
Q

Qu’est-ce qu’occasionne la perte des ganglions dans le glaucome?

A

Glaucomatous Damage :
Ganglion cell loss correlates with
- Augmentation du C:D ratio (loss of neuroretinal rim)
- VF loss
- RNFL thinning
- Post-synaptic atrophy/cell loss in LGN

25
Q

Time to death of th RGC after axonal injury? (ex. glaucome)

A

Time to death of RGC can be days to months after axonal injury
When RGC dies, there is anterograde degeneration of axon
Apoptosis main mechanism

26
Q

Qu’est-ce que l’apoptose?

A

Genetically programmed cell death
No inflammation, no necrosis
Tissue loss
Apoptosis can be triggered in neighbouring neurons when one is damaged

27
Q

Site of damage in glaucomatous damage?

A

Site of damage : OPTIC DISC
ONH changes (neural tissue)
Bowing (courbure) of Lamina Cribrosa
Accumulation of organelles in axons (blocked transport)
Anterograde (Wallerian) degeneration distal to lamina cribosa

28
Q

Quels sont les 2 théories du glaucomatous damage?

A

MECHANICAL theory : elevated IOP stretches laminar beams and damages RGC axons

VASCULAR theory : reduced ocular blood flow causing ONH damage/RGC loss

29
Q

Qu’est-ce que impaired axonal transport dans le glaucome?

A

May precede RGC death
May be reversible at this stage (by lowering IOP)
Impaired may be due to :
- Impaired anatomy (mechanical strain at ONH)
- Metabolism (mitochondria and ATP)
- Damaged cytoskeleton

30
Q

Qu’est-ce que la Lamina Cribosa?

A

Sieve-like opening in sclera at back of globe
Collagen and elastin extracellular matrix
Astrocytes and lamina cribosa cells
Overlapping and branching beams support axon bundles as they form ON

31
Q

Lien entre la Lamina cribrosa et le glaucome

A

Superior and inferior LC have larger pores, and thinner beams = clinical correlation avec VF
Progressive glaucoma shows posterior bowing and thinning of Lamina cribrosa
Previously thought to be purely mechanical
More recent work suggests remodelling of Laminar extracellular matrix

32
Q

Causes du cupping dans le glaucome

A

Due to loss of RGC’s and their axons
Due to bio-mechanical changes in Lamina Cribrosa

33
Q

ISN’T the rule dans le disc rim thickness

A

Disc rim thickness in normal patient :
- Inferior >/= Superior >/= Nasal >/= Temporal

34
Q

Quelle pathologie est associée à un non respect du ISN’T rule?

A

If rule violated, may have GLAUCOMA

35
Q

Dimensions du disque optique (moyen, petit et large)

A

Average disc size : 2 mm
Smal disc : < 1,5 mm
Large disc : > 2,2 mm

36
Q

Vrai ou Faux : « Normal » cup size depends on size of disc?

A

Vrai

37
Q

Qu’est-ce que les zones Alpha et Beta parapapillaires?

A

Parapapillary Atrophy

Alpha-zone :
- Hyper/Hypo-pigment of RPE
- Normal and glaucoma eyes

Beta-zone :
- Area with ABSENT or ATROPHIED RPE
- Choriodal vessel/sclera visible
- Associated with GLAUCOMA progression
- Size of area and enlargement = progression

38
Q

Apparence des Hg a/n du disque optique dans le glaucome?

A

Hemorrhage near disc margin in RNFL : splinter apparence

39
Q

Théories derrière les Hg du disque optique

A

Vasculaire : vessel Hg at disc = axon ischemia and loss

Mechanical : pre-existing disc damage (ex. notch) gives collapse of tissue, stain on vessel then bleed

Gliosis : Glaucomatous damage causes localized gliosis. Contraction of scar causes capillary damage at junction of glial and normal tissue (border of RNFL defect)

40
Q

Où sont principalement localisés les Hg du disque optique? Quelle est la durée d’une Hg du disque?

A

2/3 occur inferotemporal
Often occur in area of previous damage (notch, RNFL defect, PPA)
On average last 2-3 mois (donc si présence persistante d’un Hg au FO au suivi de 6 mois = nouvelle Hg et non la même)

41
Q

Les Hg du disque optique sont ils associés à une progression du glaucome?

A

Oui.

Hemorrhage strongly associated with progression and active disease

Often subtle and easily missed on exam

42
Q

Autres FdR associés au glaucome

A

Ocular Perfusion Pressure
- Perfusion pressure = Pa-Pv (IOP)
- Perfusion pressure is reduced when : arterial pressure reduced + increased IOP = lower blood flow
- Ex. Migraine = vasospasme = affecting ocular blood flow

CSF pressure
- Pressure difference between intra ocular and CSF space
- Lamina cribrosa divides the 2 spaces (différence entre les 2 compartiments)
- Low CSF pressure compared to IOP may contribute to damage at optic disc
- Pressure gradient - depends on pressure difference AND distance between the compartments
- Ocular hypertensives had significantly higher CSF pressure
- CSF pressure is correlated with blood pressure

CSF turnover

TORIC (17 decks)

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