Physiology Flashcards
Where is CSF made?
By the secretory epithelium of the choroid plexus in the ventricles of the brain
How much CSF is produced a day?
500-600ml/ day
What is the function of CSF?
Mechanical protection
Homeostatic function
Circulation
How does the CSF act as mechanical protection?
Shock-absorbing medium that protects brain tissue. Brain “floats” inside cranial cavity
What homeostatic function does the CSF provide?
pH of CSF affects pulmonary ventilation and cerebral blood flow
Transports hormones
What role does the CSF have in circulation?
Medium for mior exchange of nutrients and waste products between blood and brain tissue
How is CSF analysis performed?
Lumbar puncture - aids the diagnosis of brain, meninges and spinal cord
What should normal CSF fluid look like?
Clear and colourless, contains little protein (15-45 mg/dl) and little immunoglobulins (1-5 cell/ml)
How does hydrocephalus develop?
Obstruction of CSF outflow with resulting enlargements of ventricular spaces upstream of the blockage
Bones of the developing skull move apart and head will enlarge
May need CSF shunt
When does the brain begin to develop?
3 weeks post conception
What is a choroid plexus?
Arteries invaginated in the ventricle to form villi surrounded by enedymal cells
Where can choroid plexuses be found?
Lateral ventricles
3rd ventricle
4th ventricle
How is CSF produced in the choroid plexus?
CSF secretion involves the transport of ions (sodium, chloride and bicarbonate) across the epithelium from blood to CSF
What doe secretion of fluid by the choroid plexus depend on?
The active sodium transport across the cells into the CSF. The electrical gradient pulls along chloride and both drag water via osmosis
What are the differences in electrolytes between the plasma and CSF?
CSF has lower potassium, glucose and protein
CSF has higher sodium and chloride
Does CSF production depend on arterial pressure?
No, it is an active secretory process
What connects the lateral ventricle to the 3rd ventricle?
Interventricular foramina of monroe
What connects the 3rd ventricle to the 4th?
Cerebral aqueduct of sylvius
What connects the 4th ventricle to the subarachnoid space?
Foramen of magendie
Foramen of Luschka
Describe the circulation of CSF?
CSF formed in choroid plexus of lateral ventricles
Flows to 3rd ventricle via foramina of monroe
More CSF added in 3rd ventricle
Flows through cerebral aqueduct of sylvius to the 4th ventricle
4th ventricle adds more CSF
CSF enters subarachnoid space via foramen of magendie and luschka
Circulates central canal of spinal cord
Returns to venous blood via superior sagittal sinus
Where is the subarachnoid space?
Between pia and dura mater
What makes up the blood brain barrier?
Capillary endothelium, basal membrane and perivascular astrocytes
Tight junctions between brain endothelial cells prevent paracellular movement of molecules
What does the BBB protect the brain from?
Common bacterial infections and toxins
Determining factor for clinical CSF analysis
Main obstacle for drug delivery to CNS