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Ophthalmology > Physiology and Immunology > Flashcards

Physiology and Immunology Flashcards

1
Q

what is a choroid fissure

A

when developing arteries invaginate into the roof of the ventricle

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2
Q

What is the choroid plexus

A

made up of ependymal cells and vessels enlarging into villi

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3
Q

What is CSF made up of

A

mainly water

the rest is made up of brain interstitial fluid

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4
Q

How does the interstitial fluid get into the CSF

A

drains via perivascular spaces

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5
Q

What are the functions of CSF

A

Protects the brain - shock absorption
pH of CSF affects pulmonary ventilation and cerebral blood flow
transports hormones

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6
Q

what is the blood-CSF barrier

A

a leaky barrier that allows drainage of CSF into the subarachnoid space

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7
Q

What is the blood-brain barrier

A

a non leaky barrier

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8
Q

What does the blood-brain barrier consist of

A

capillary endothelium
its basal membrane
perivascular astrocytes

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9
Q

How does the blood-brain barrier work

A

there are tight junctions between the endothelial cells that doesn’t let anything pass

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10
Q

Where can a colloid cyst usually be found

A

posterior to the foramen of monroe in the anterior aspect of the 3rd ventricle

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11
Q

What is an ependymoma

A

a cancer derived from ependymal cells

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12
Q

What is a subdural haemorrhage

A

venous haemorrhage between the dura and arachnoid

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13
Q

What is an epidural haemorrhage

A

an arterial haemorrhage between the skull and the dura

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14
Q

What is a subarachnoid haemorrhage

A

blood leaking into the subarachnoid space

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15
Q

Hydrocephalus is

A

accumulation of CSF in ventricular system/ around the brain causing increased CSF pressure

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16
Q

What are the causes of hydrocephalus

A

over-production of CSF

obstruction

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17
Q

What is idiopathic intracranial hypertension also known as

A

pseudotumour cerebri

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18
Q

What does idiopathic intracranial hypertension present with

A

headache
visual disturbance
papilloedema
ICP on lumbar puncture with no imagining of hydrocephalus

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19
Q

What are the risk factors for IIH

A

obesity/ recent increase in weight

tetracycline

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20
Q

What is the function of aqueous humour

A

provides - oxygen

  • metabolites
  • HCO3 for buffering against H+ which is produced in anaerobic glycolysis of the cornea and lens
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21
Q

Where is aqueous humour produced

A

ciliary body

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22
Q

What is the ciliary body and posterior iris made up of

A

2 contrasting layers of epithelium (pigmented epithelium overlain by non-pigmented)

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23
Q

What does Carbonic anhydrase allow

A

production of HCO3

transport of HCO3 into the posterior chamber (along with Na, K, Cl and water)

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24
Q

what is the pathway of the retina

A

photoreceptors -> bipolar cells -> ganglion cells

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25
Q

Where does horizontal cells get their input from

A

bipolar cells

photoreceptors

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26
Q

where does amacrine cells get their input from

A

bipolar cells
ganglion cells
other amacrine cells

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27
Q

What do photoreceptors do

A

transduction - change electromagnetic radiation (APs) into neural signals

28
Q

In the dark/at rest, what happens to the Na

A

Na enters the outer segment and leaves via the inner segment, driven by the presence of K

29
Q

What is the ratio of Na to K in the outer segment

A

Na=K

30
Q

What is the dark current

A

cGMP gated Na channels are open in the dark and close in the light

31
Q

What happens to the cell in the light

A

the channels on the outer segment of the photoreceptor close meaning Na can’t enter so K>Na
- this causes the cell to hyperpolarise (Vm becomes more -ve)

32
Q

How is the brain able to perceive objects in the visual field

A

Due to the change in Na in the photoreceptors

33
Q

Rhodopsin =

A

rods

made from retinal (Vit A derivative) and opsin (G protein coupled receptor)

34
Q

where are rods present

A

on the discs in the outer segment of the photoreceptor

35
Q

What does light to do the rods

A

changes 11-cis-rhodopsin to all-trans-rhodopsin (vitamin A)

36
Q

what does all-trans-rhodopsin do

A

activates transducin which causes a molecular changed causing a decrease in cGMP
- this in turn closes cGMP gated Na channels and hyperpolarisation of the cell

37
Q

what is visual acuity

A

the ability to differentiate to distinct nearby points

38
Q

How is visual acuity determined

A

by photoreceptor spacing and refractive power

39
Q

What do rods do

A 
see dim light
achromatic (black and white) 
in peripheral retina 
high convergence
high sensitivity to light 
low visual acuity
40
Q

what do cones do

A 
see daylight light 
chromatic (colours) 
in central retina (fovea) 
low convergence 
low light sensitivity 
high visual acuity
41
Q

what is amblypoia

A

cortical blindness (lazy eye)

42
Q

what can ambylopia be caused by

A

strabismus if not corrected in infancy

43
Q

what is strabismus

A

where both eyes do not align when looking at an object

44
Q

what is the treatment for strabismus

A

child has to wear a patch on their good eye for a couple of hours a day (so brain can properly develop both eyes) till they become of age to get surgery

45
Q

What is Hebbs postulate

A

loss of binocularity (everything looks fuzzy)

46
Q

How does hebbs postulate occur

A

when an axon is too close to another cell, it will excite that cell leaving the axon of that cell redundant

47
Q

What are the layers of the tear film

A

mucin layer (non-adhesive)
aqueous layer
lipid layer

48
Q

What does the blink reflex do

A

washes lacrimal fluid to the centre of the eye

49
Q

Where are langerhans cells found

A

abundant in the corneal scleral limbus
less in peripheral cornea
absent in the central cornea

50
Q

Lymphatic drainage of the eye is only found where

A

conjunctiva

51
Q

The cornea and the sclera are

A

a tough collagen coat
avascular
no lymphatic drainage

52
Q

what makes up the blood-ocular barrier

A

vitreous
choroid
retina

53
Q

What is immune privilege

A

ares of the body that can tolerate an antigen without producing an inflammatory immune response

54
Q

Which sites in the eye have immune privilege

A 
cornea
lens 
anterior chamber
vitreous chamber
subretinal space
55
Q

what is anterior chamber associated immune deviation (ACAID)

A

protects the eye and visual axis from collateral damage of an immune response by suppression of a future response to infection

56
Q

How doe ACAID work

A

produces CD4+ T and B cells that produce non-complement fixing Ab
inhibits type 4 hypersensitivity which usually would secrete complement fixing Ab
therefore, inhibits immune response

57
Q

Where is ACAID present

A

cornea

58
Q

What does ACAID do in cornea

A 
means there is reduced MHC class 1 and no MHC class 2
- no blood or lymphatic vessels
59
Q

What is sympathetic ophthalmia caused by

A

surgery/ trauma to one eye

immune (T cell mediated) response

60
Q

what does sympathetic ophthalmia present as

A

bilateral granulomatous uveitis

61
Q

What is the treatment for sympathetic ophthalmia

A

need to remove the damaged eye to prevent loss of both eyes

62
Q

What is type 1 hypersensitivity and give an ocular example

A

immediate response
mediated by IgE
e.g. acute allergic conjunctivitis
chemosis (oedema of conjunctiva)

63
Q

What is type 2 hypersensitivity and given an ocular example

A

direct cell killing
mediated by complement , NK cells and macrophages
e.g. ocular cicatrical pemphigoid

64
Q

What is type 3 hypersensitivity and given an ocular example

A

Immune complex mediated
mediated by T, B cells and Ab
e.g. autoimmune corneal melting

65
Q

What is type 4 hypersensitivity and given an ocular example

A

delayed hypersensitivity
mediated by Th cells
e.g corneal graft rejection

Ophthalmology (8 decks)

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