CSF production & circulation

Question 1

main function of the CSF?

Answer 1

to cushion the brain- have the same specific gravity

Question 2

Describe the formation and path of flow of the CSF

Answer 2

secreted from the choroid plexus (in lateral vesicles)
additional fluid secreted by the ependymal surfaces of all the ventricles & arachnydal ventricles

flow: begin in the choroid plexus
lateral ventricles to 3rd ventricle to aqueduct of sylvius to 4th ventricle to 2 lateral foramina of luschka to midline foramen of magendie to cisterna magna
then flow up around the subarachnoid spacesand through the arachnoidal villi & into venous blood

Question 3

Secretion by the choroid plexus

• structure of choroid plexus
• mechanism of secretion (ion transport in an out)

Answer 3

-cauliflower like growth, blood vessels + thin layer of epithelial cells

-secretion depends on active transport of Na ions through the epithelial cells
Na ions bring CL with them so increasing the quantity of osmotically active NaCl in CSF causing osmosis of water through the membrane
glucose also moves in while K and bicarb transported out

Question 4

Perivascular spaces

• what are they?
• what do they do?

Answer 4

• space between each vessel and the pia mater

- act as a specialised lymphatic system for the brain through which proteins and infectious debris are transported

Question 5

cerebrospinal fluid pressure

• regulated by what
• if the mechanism fails and example

Answer 5

-arachnoidal villi, at like valves, fluid can easily flow into venous circulation but not vice versa
flow occurs when CSF pressure is greater than the pressure in the blood

• in disease the villi might become blocked and lead to high CSF pressure
  e. g. hydrocephalus

Question 6

name the 3 tumours that might effect CSF

Answer 6

colloid cyst (interventricular foramen)
ependymomas (ependymal cells lining the ventricles)
choroid plexus tumours

Question 7

name the 3 causes of ventricular haemorrhage

Answer 7

epidural haemaotoma (arterial bleed between skull and dura)
subdural haematoma (venous blood between dura and arachnoid)
subarachnoid haemorrhage

Question 8

What is hydrocephalus

Answer 8

accumulation of CSF in the ventricular system

1+ ventricles enlarge and increased CSF pressure

Question 9

symptoms of idiopathic intracranial hypertension (2)

Answer 9

enigmatic headaches & visual disturbance due to papilloedema

Question 10

what is papilloedema

-presentation

Answer 10

optic disc swelling due to incraesed intracranial pressure transmitted to subarachnoid space around the optic nerve

-enlarged blind spot
blurred vision
visual obstruction
loss of vision

Question 11

aqueous humour production

• what is it?
• produced where?
• path of flow
• covering of where it is produced

Answer 11

-fluid that bathes structures in the eye , contains O2 metabolites and bicarbonate
it buffers the H+ produced by the cornea and the lens

• in the epithelium of the ciliary body
• from the post chamber of the eye to the anterior chamber through the pupil and then to the scleral venous sinus and the canal of schlem
• ciliary body covered in juxtaposed layers of epithelium : pigmented and non-pigmented

Question 12

ionic composition of aqueous humour

- mechanism by which this is achieved

Answer 12

HCO3 and H are transported into interstitial fluid in exchange for Cl and Na
Cl and Na then diffuse through the gap junctions between PE and NPE cells and are then transported out of NPE cells into aqueous humour
net movement is accompanied by water moving through ciliary epithelial aquaporins