Blood-CNS barriers Flashcards
Vascular supply of the brain
Carotid arteries+vertebral arteries->circle of willis, pial arteries, penetrating arteries, penetrating arterioles, intracerebral arterioles,, capillaries
Sketch the neurovascular unit and the blood-brain barrier
ref. notes
How do the astrocytes and he capillaries interact
end feet of astrocytes form rosette like structures. Astrocytes have more than one end feet and each endothelial cell can receive end feet from more than one astrocytes
what are the functions of astrocytes
1) energy and nutrient support of neurones
2) ion and water homeostasis
3) termination of sympathetic activities
4) maintenance of the blood brain barrier
5) breathing regulation
What are the permeation mechanisms of the blood to and from the tissues
simple diffusion, passive diffusion, transporters influx, transporters efflux, endocytosis
What type of junctions are there to allow paracellular movement
Tight junction (claudin, occludin, Junctional Adhesion molecule, endothellial selective adhesion molecule) Adherens junction (platelet endothelial cell adhesion molecule, vascular endothelial-cadherin juncttion
Morphine, codeine, heroin how well do they pass through BBB and mention anything of note
Heroin>codeine>morphine in terms of permeability, Once heroin enters brain, converts to morphine meaning it remains in brain. Morphine can also convert into codeine
How are amino acids transported across BBB
transporters that transport groups of AA are simillar size and charge. Some of these transporters are polarised (only expressed on abdominal/luminal surface. Some transporters rely on Na+. Some are facilitated transporters
Why is D glucose above prediction for permeability
Because glucose can use transporters to cross BBB
What are the efflux transporters in the CNS
P-glycoprotein (only on luminal surface), Breast Cancer Resistance Protein, multi drug resistance associated protein NB drugs can go into the endothelial cell but not the brain->returns to blood
What are the key features of the cerebral capillary endothelium
Continuous strands of tight junctions, high levels of transporters, reduced numbers of vesicles/fenestrations, has metabolic barriers (enzyme systems) so that molecules can enter cell but not cross abluminall membrane because 1) actively extruded back to blood 2) becomes more polar, less lipophilic, unable to passively diffuse acrosss abluminaal membrane
What kind of endocytosis and transcytosis happen from blood to brain
non selective fluid phase endocytosis, selective receptor-mediated transcytosis e.g. insulin, transferrin, selective absorptive transcytosis e.g. albumin, other plasma proteins
What are the functions of the BBB
(Controls molecule influx into brain ISF
suppllies brain with essential nutrients
mediates efflux on waste products
restricts ionic and fluid movements)
->protects brain from fluctuations in ionic composition observed in plasma
provides brain with sstable ISF and optimal environment for neuronal function
Choroid plexus fuction
produces CSF, synthesises polypeptide->contributes to regulating blood ISF
Which ways do the ions get transported in the plexus epithelium
Na+, K+, Cl- and HCO3- gets transported into CSF
Primary driiving force=Na-K+ ATPase pump. Maintains low intracellular Na+. Promotes secondary active transport of Na+-H+, HCO3–Cl-
H2O follows through aquaporin I
