CSF

Question 1

Functions of CSF (3)

Answer 1

• Mechanical support for the central nervous system (CNS)
• Provides hormones, nutrients, ions, and growth factors to CNS
• Helps to maintain a constant external environment for neurons and glia by removing waste products from the CNS

Question 2

Origin of CSF

Answer 2

• made by choroid plexus (secretory epithelial cells + connective tissue w/ fenestrated capillaries
  
  • In wall of lateral and 3rd ventricles and roof of 4th ventricle
  • Tight junctions b/n epithelial cells forms blood-CSF barrier
  • Microvilli and cilia on apical surface (face into ventricle)
  • Sep from connective tissue layer by basement membrane

Question 3

What is the role of active transport on choroid plexus epithelial cells?

Answer 3

Transporters/channels help maintain CSF concentrations that are different than serum

• Epithelial cells express channels (active transport to filter serum –> CSF)
  
  • NKCC1 (Na-K-Cl co transporter) and Aqp1 (water)

Question 4

What are the differences in composition between CSF and serum?

Answer 4

CSF has less protein, glucose, K+, Ca++ than serum

CSF has more Cl-, Mg++ and water than serum

Question 5

How is ICP normally regulated?

Answer 5

• Monro-Kellie Hypothesis: Vbrain + Vblood + Vcsf = Vk (constant volume)
• Change in one component –> compensatory change in another
  • Ex) Inc ICP –> compensate by dec cerebral blood flow –> brain ischemia
    
    • Cerebral perfusion pressure (CPP) = MAP -ICP (so inc inc ICP can dec perfusion)

Question 6

Causes of Inc ICP (4)

Answer 6

1- Space occupying masses (tumors, edema, intraparenchymal hemorrhage)

2-Absorption of CSF is blocked (if blockage in 3rd ventricle - lateral dilated AKA space above will be dilated)

3- Too much CSF prod

- Ex) hydrocephalus (dilation of ventricles usually due to excess CSF in intracranial cavity - but can still be dilated if normal pressure)
    - Non-communicating or Obstructive - if flow blocked w/in ventricular system
    - Communicating or Non-Obstructive- CSF reabsorption is impaired, too much CSF prod pr CSF flow is blocked in subarachnoid space
    - **Hydrocephalus in neonates can result in increased head circumference b/c sutures have not fused so skull expands to reduced inc ICP

4-Genetic disorders
- Ex) Arnold-Chiari Malformation - cerebellar tonsils in foramen magnum –> SC; blocks CSF outflow through foramina of Magendie and Luschka; leads to enlargement of all brain ventricles –> compresses neural tissue

Question 7

Regional Diff In CSF

Answer 7

• CSF flows top–> down SO… CSF in 3rd and 4th ventricles may be different than that of lateral ventricles; BUT lateral ventricle CSF will flow down into 3rd and 4th ventricles
• CSF prod in diff ventricles may have diff content (ex - protein content or diff molecules for repair)
• Due to diff transcriptomes
• Implications
  
  • Could treat specific region; region-specific CSF supplement
  • Regional diff could impact normal development