Physiology of CSF Flashcards
What is the CSF produced by?
choroid plexus
What is the volume of CSF in the CNS?
150ml
How often is the CSF in the CNS replaced every day?
3-4 times a day
What are the 3 functions of CSF?
Mechanical protection: shock absorbing so protects brain tissue
Homeostatic function: pH of CSF affects pulmonary ventilation and cerebral blood flow, also transports hormones
Circulation: medium for minor exchange of nutrients and waste products between blood and tissue
How is CSF analysed?
lumbar puncture
How does normal CSF look?
clear and colourless, contains little protein (15-45mg/dl), little immunoglobulin and only a few cells (1-5 cells)
What does CSF production rely on?
the transport of Na, Cl and HCO3 across the epithelium from blood to CSF, through ACTIVE NA TRANSPORT
This electrical gradient pulls along Cl and both Na and Cl pull water by osmosis
What are CSFs properities of K, glucose, protein, Na and Cl compared to plasma?
lower K, glucose and protein
higher Na and Cl
than plasma
Is CSF production dependant on BP?
NO - it is an active secretory process
What does the brain start as?
the neural canal
What do the cavities of the neural canal give rise to?
ventricles and the central canal of the spinal cord
How does the choroid plexus develop?
the developing arteries invaginate (fold back on themselves forming a pouch) the roof of the ventricle to form the choroid fissure the involouted (small again) ependymal cells along the vessel enlarge to form villi and form the choroid plexus
In which ventricles are the chroid plexus formed in (in the adult brain)?
lateral, 3rd and 4th
What is the role of the choroid plexus?
absorbs plasma from the circulation and secretes it as CSF
What enables CSF to be secreted outwards?
3rd, 4th and lateral ventricles all connect together
