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2 Ophthalmology > Physiology of CSF > Flashcards

Physiology of CSF Flashcards

1
Q

what is CSF

A

a clear, colourless liquid composed mostly of water

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2
Q

where is CSF produced

A

the secretory epithelium of the choroid plexus (in the ventricles)

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3
Q

what is the volume of CSF at one time (replaced every 3-4 days)

A

150 ml

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4
Q

what does the CSF circulate in

A

subarachnoid space

between the arachnoid and pia mater

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5
Q

what does the CSF supply/remove from the brain

A

supplies water, amino acids, ions

removes metabolites

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6
Q

what are the 3 main functions of CSF

A
  1. mechanical protection (shock absorbing medium that protects brain tissue)
  2. homeostatic function (pH of CSF affects pulmonary ventilation and cerebral blood flow - transports hormones
  3. circulation (minor exchange of nutrients and waste products between blood and brain tissue)
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7
Q

how is clinical CSF analysis obtained

A

lumbar puncture

aids the diagnosis of the brain, meninges and spinal cord

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8
Q

what does normal CSF look like

A

clear
colourless
contains little protein and little immunoglobulins

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9
Q

how many cells are there per 1 cml of CSF

A

1-5

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10
Q

what does the developing nervous system look like at 3 weeks

A

the neural canal/tube

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11
Q

what does the neural canal give rise to in the human brain

A

the ventricles and the central canal of the spinal cord

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12
Q

what does the choroid plexus develop from c

A

cells in the walls of the ventricles

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13
Q

what cells produce CSF

A

Choroidal cells (in the choroid plexus)

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14
Q

how is the choroid fissure formed

A

developing arteries press the roof of the ventricle inside out to produce the choroid fissure

this then develops into the choroid plexus

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15
Q

where is the choroid plexus found in the adult brain

A

the 3rd and 4th and lateral ventricles

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16
Q

what ions are transported across the epithelium from blood to CSF to allow CSF secretion

A

Na+
Cl-
HCO3-

transferred across the epithelium from blood to CSF

17
Q

what is the circulation of CSF

A

choroid plexuses of the lateral ventricles

then to 3rd ventricle via the inerventricular foramen

more CSF is added by the choroid plexuses of the 3rd ventricle

then flows through aqueduct of midbrain (cerebral duct) into 4th ventricle

choroid plexus un 4th ventricle adds more CSF

then enters subarachnoid space via 4th ventricle - goes through the lateral apertures or the median aperture

circulated in the central canal of the spinal cord

18
Q

how does CSF return to venous blood

A

through arachnoid granulation into the dural sinus

19
Q

what restricts the blood supply to the majority of the brain

A

blood brain barrier

20
Q

how does the brain interstitial fluid drain into the CSF

A

via the perivascular spaces

21
Q

what makes up the blood brain barrier

A

endothelial cells in brain capillaries

tight junctions between brain endothelial cells prevent paracellular movement of molecules

22
Q

what parts of the brain do not have a blood brain barrier

A

circumventricular organs

pineal gland

23
Q

what does the BBB protect the brain from

A

bacterial infections and toxins

24
Q

what pathology can affect the ventricles, choroid plexus and CSF

A

Tumours
Ventricular haemorrhage (accumulation of blood in the ventricles)
Hydrocephalus
Idiopathic intracranial hypertension

25
Q

what tumours can affect the ventricles, choroid plexus and CSF

A
  • colloid cysts (often found in inter ventricular foramen)
  • ependyomonas (arising from ependymal cells lining the ventricles)
  • choroid plexus tumours
26
Q

where are common haemorrhages which can affect the ventricles, choroid plexus and CSF found

A

epidural hematoma (arterial bleed between skull and dura)

subdural hematoma (venous bleed between dura and arachnoid)

subarachnoid haemorrhage

27
Q

what is hydrocephalus

A

accumulation of CSF in the ventricular system or around the brain (either due to obstruction or overproduction)

Subsequent enlargement of one or more ventricles and increase in CSF pressure

28
Q

what is idiopathic intracranial hypertension/pseudotumour cerebri

A

symptoms include headache and visual disturbances due to papilloadema (bulging of optic disc)

increased CSF pressure but no imaging features of hydrocephalus

29
Q

what does hydrocephalus look like on MRI

A

Swelling of the lateral ventricles

30
Q

what is papilloedema

A

optic disc swelling due to increased intracranial pressure

31
Q

visual symptoms of papilloedema

A

enlarged blind spot
blurring of vision
visual obscurations
loss of vision

32
Q

what is aqueous humour

A

specialised fluid that bathes try structures within the eye

provides oxygen and metabolites and contains bicarbonate

33
Q

why does aqueous humour contain bicarbonate

A

to buffer the H+ produced in the cornea and lens by anaerobic glycolysis

34
Q

where is aqueous humour produced

A

ciliary body

via an energy dependent process in the epithelial later

35
Q

what route does aqueous humour take after it has been secreted

A

ciliary body — posterior chamber — anterior chamber (via pupil) — lacrimal canal/canal of schlep –nasolacrimal duct

36
Q

what two juxtaposed layers of epithelia calls cover the ciliary body and posterior surface of the iris

A

pigmented epithelium of the retina

non pigmented epithelium of the retina

37
Q

why must the aqueous humour contain bicarbonate

A

so it can be exchanged for Na+ and Cl- ions to come into the ciliary body and bring water

38
Q

how can you control the levels of aqueous humour

A

by blocking the production of bicarbonate with carbonic anhydrase inhibitors

these therefore reduce ocular pressure in glaucoma

39
Q

what are 2 commonly used carbonic anhydrase inhibitors

A

dorzolamide (eye drops)

acetazolomide (oral- also targets kidneys)

2 Ophthalmology (16 decks)

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