Blood-brain barrier

[Ref: KB2:p225]

Blood-brain barrier

Tight junctions between capillary endothelial cells

Blood-CSF barrier

Tight junction between choroid plexus epithelial cells

NB:

• Separated from blood by blood-brain barrier
• Only lipid soluble substance can easily cross
• Glucose passively diffuse across blood-brain barrier
  * Faciliated by GLUT1 channels

Substances which cross BBB easily

• O2
• CO2
• Lipid soluble substnces
• Water (though still slower than through normal capillaries)
• Na+
  * Also actively transported into CSF in the choroid plexus