Physiology Flashcards
main component of CSF
water
what produces CSF?
secretory epithelium of the choroid plexus
how much ml of CSF is made per day?
500ml
how much CSF is present in the CNS?
150ml
how many choroid plexuses are there and where are they located?
4
the ventricles of the brain
explain the direction CSF travels in starting from its production
lateral ventricles via interventricular foramina to 3rd ventricle via aqueduct to 4th ventricle subarachnoid space venous circulation
3 main functions of CSF
protect brain tissue
maintains homeostasis
create a medium between BBB
how is CSF tested clinically?
lumbar puncture
what should normal CSF look like?
clear
colourless
CSF has lots of proteins and antibodies T or F
F, has very little
cause of hydrocephalus?
accumulation of CSF in the brain due to overproduction or obstruction
what does the choroid plexus derive from embryologically?
cells in the walls of the ventricles
what ventricles is choroid plexus found in?
3rd
4th
lateral (2)
what is the choroid plexus?
networks of capillaries in walls of the brain ventricles
what causes the secretion of cerebrospinal fluid?
ions eg Na needing to be transported from the blood
why is the CSF mainly composed of water?
water crosses the membrane from the blood because ions have crossed (osmosis)
what separates the lateral and third ventricles?
foramina of monroe
what separates the 3rd and 4th ventricles?
cerebral aqueduct
what makes up the final portion of CSF?
brain interstitial fluid
what cells are the site of the blood brain barrier?
endothelial cells in brain capillaries
3 layers of the blood brain barrier?
capillary endothelium
basal membrane
perivascular astrocytes
main obstacle for drug delivery to the CNS?
BBB
common location for a colloid cyst?
often at the interventricular foramen
patient with headache and poor vision; no sign of hydrocephalus on CT but dos have increased CSF pressure?
idiopathic intracranial HT
what is papilloedema?
optic disc swelling due to increased intracranial pressure
what causes the visual loss in papilloedema?
subarachnoid space surrounds the optic nerve and when there is increased pressure there it will compress the nerve
visual symptoms of papilloedema?
enlarged blind spot
blurred vision
visual obscurations
loss of vision
is Cl more concentrated in the blood or CSF?
CSF
causes of papilloedema?
increased cranial pressure
inadequate CSF drainage
what makes aqueous humour?
ciliary body
where is the ciliary body?
lateral to the lens
name the 2 layers covering the ciliary body?
pigment epithelium of the retina
non pigmented epithelium of the retina
how to ions get to and from the pigmented and non pigmented epithelial cells
gap junctions
what molecule is essential for aqueous humour present?
HCO3
cause of the raised intraocular pressure in glaucoma?
imbalance between the rates of secretion and removal of aqueous humour
what kind of signal does light have to be in order to be processed by the brain?
electrical
where do the ganglion cell axons project to in the retina?
the forebrain
what structures of the eye focus light on the retina?
cornea
lens
list the 4 main regions of a photoreceptor
outer segment eg rod/cone
inner segment
cell body
synaptic terminal
is the resting Vm of photoreceptors more positive or negative than other neurons?
positive
what effect does light have on the Vm of photoreceptors?
hyperpolarises it (makes it more negative)
why is the Vm of a photoreceptor so positive?
cGMP gated Na channel is OPEN in the dark and closes when there is light
main visual pigment in rods?
rhodopsin
average current of a photoreceptor?
-29 to -40mV
what does rhodopsin consist of?
retinal + opsin
what does the retinal part of rhodopsin do?
activates transducin (GPCR) which activates cGMP to close Na channels
what kind of vision do rods allow?
seeing in dim light
what kind of vision do cones allow?
seeing in normal daylight
do rodes or cones have higher convergence and why?
rods
want to have more sensitive (eg to light) than acute vision
what does high convergence mean?
large spacing and number of cells to one ganglion
where in the retina are rods located?
peripheral retina
where in the retina are cones located?
centrally
do cones or rods provide visual acuity?
cones
what is retinotopy?
separation of the retina
