NEURO physiology

Question 1

What is the volume of CSF within a standard adult? what is the rate of production ?

Answer 1

150ml, rate of 20ml/hour or 450ml/day.

Question 2

Functions of CSF

Answer 2

-cushioning and buoyancy of the brain
- maintaining constant ionic environment
- removal of waste
- aids in central control of respiration, poor buffering capacity results in reduction of CSF pH which is detected by central chemoreceptors
- role in buffering ICP changes

Question 3

Circulation of CSF from secretion to absorption

Answer 3

Choroid plexus in lateral ventricles -> foramen of munro -> third ventricle -> aqueduct of sylvius -> fourth ventricle -> lateral foramen Luschka and foramen magendie -> sub arachnoid space -> reabsorbed in arachnoid villi.

Question 4

how does CSF differ to plasma (4)

Answer 4

• Reduced pH (7.32)
• Reduced protein (reduced buffering)
• Increased chloride concentration
• Reduced glucose concentration

Question 5

What is the BBB

Answer 5

Barrier at the level of the capillaries where plasma constituents cannot freely pass into the CSF

Question 6

Transport processes across BBB (4_)

Answer 6

• simple diffusion (small, lipid soluble -> ethanol, hormones, o2/co2)
• active xport - ions
• facilitated diffuision - specific molecules/transporters (aquaporins, glut-1
• pinocytosis - insulin

Question 7

Anatomical structure of BBB

Answer 7

• Tight junctions between capillaries that supply brain - restricted passage
• Astrocyte foot processes reduce endothelial permeability
• Thick basement membrane beneath endothelium