Physiology Flashcards
Where is CSF produced?
Secretory epithelium of the choroid plexus (found within the ventricles)
Where does CSF travel to beyond the ventricles?
Circulates in the subarachnoid space and absorbed in the venous circulation
What are the three major functions of the CSF?
Mechanical protection
Homeostatic function
Circulation
Describe the homeostatic function of CSF
pH affects pulmonary ventilation and cerebral blood flow/ transports hormones
What can a lumbar puncture aid to diagnose?
Pathology in the brain, meninges and spinal cord
Describe the components of normal CSF?
Clear and colourless
Contains (14-45mg/dl)
Little immunoglobulins
1-5cells/ml
At three weeks the developing nervous system consists of
Neural canal
What does the cavity of the neural canal give rise to?
Adult brains ventricles and the spinal cords central canal
Where does the choroid plexus develop from?
Cells in the walls of the ventricles
What forms the choroid fissure?
Developing arteries invagination the roof of the ventricle
Which ventricles can choroid plexi be found in?
3rd, 4th and lateral ventricles
What ions are transported across the epithelium from blood to CSF in CSF production?
Na
Cl
HCO3
What does secretion of CSF from the choroid plexus depend upon?
Active transport of Na across cells into CSF
What is the intraventricular foramina (of monroe)?
Lateral ventricles to third ventricle
What is the cerebral aqueduct of sylvius?
Third to fourth ventricle
What is the foramen of megendie?
Median aperture- fourth ventricle to subarachnoid space
What is the foramen of luschka?
Lateral apertures- fourth ventricle to subarachnoid space
CSF enters the subarachnoid space through
pores
Which ventricle is CSF formed in?
Lateral ventricles
Describe the path of CSF from the lateral ventricle
Alows to third ventricle through the interventricular foramina
more CSF is added by chroroid plexus in roof of third ventricle
flows through the aqueduct of midbrain (cerebral aqueduct)
and into the fourth ventricle
another choroid plexus in fourth ventricle adds more CSF
CSF then enters the subarachnoid space (between pia and dura mater) through three openings in rood of fourth ventricle
single median aperture
paired lateral apertures
then circulates in the central canal in the spinal cord
How does CSF return to the venous blood?
arachnoid granulations into the superior sagittal sinus
The blood CSF barrier is
leaky
What does the BBB consist of?
capillary endothelium, basal membrane and perivascular astrocytes
What is the role of tight junctions in BBB
Prevent paracellular movement of molecules
Which parts of the brain lack BBB
Circumventricular organs or pineal gland
What does the BBB protect against?
common bacterial infections and toxins
What is the main barrier for drug delivery to the CNS?
BBB
What tumours can be found in the ventricles, choroid plexus?
Colloid cyst: interventricular foramen
Ependymomas: ependymal cells lining ventricles
Choiroid plecus tumours
What kinds of haemorrhage cause accumulation of blood in the ventricles?
Epidural haematoma
Subdural Haematoma
Subarachnoid haemorrhage
What is an epidural haematoma?
Arterial bleed between skull and dura
What is a subdural haematoma?
venous bleed between dura and arachnoid
What is hydrocephalus?
Accumulation of CSF in the ventricular system or around the brain
What is idiopathic hypertension/pseudotumour cerebri
Increased CSF pressure with no imaging features of hydrocephalus
What are the symptoms of pseudo tumour cerebri?
Headache
Visual disturbances
What does aqueous humor provide?
Oxygen, metabolites, bicarbonate
What is the purpose of bicarbonate in aqueous?
Buffers the H+ produced in the cornea and lens by anaerobic glycolysis
What is the role of ascorbate in the aqueous?
Powerful antioxidant
Describe the path of aqueous ?
Produced by ciliary body in posterior chamber of eye
Flows into anterior chamber and drains into scleral venous sinus through a trabecular meshwork and the canal of schlemm
A small amount is passed into vitreous
Where is the canal of schlemm situated?
Iridocorneal angle
What is the pigmented epithelium?
Faces the blood inside the ciliary epithelium
What is the non-pigmented epithelium?
Lined the inside of the retina and generates aqueous humour
What blocks the production of aqueous?
Carbonic anhydrite inhibitors
How do carbonic anhydrase inhibitors work?
Prevents the transport of cl and Na into the cell
What causes the movement of water through aquaporins?
net trafficking of ions an osmotic gradient is generated causing the movement of water via aquaporins
