Neuronland: NeuroTeach 49 - Blood-brain barrier & circumventricular organs

Blood-brain barrier & circumventricular organs

German physician Paul Ehrlich (1854-1915)

2) Paul Ehrlich (1882)

After IV injection of trypan blue, most brain areas did not get stained - these areas are inside BBB Some areas of brain get stained. - these areas do not have BBB

3) Function

Neurons are like ladies. They are very sensitive. So, the function of BBB is like a mother: STABILIZE when they become sad PROTECTS from the toxins of the world HOLD YOU to maintain the concentrations

4) BBB is formed by “BBB”

Binding tight junctions Basement membrane Base-foot astrocyte

5) Capillary

Have 3 types of capillaries in the body  CSF Continuous – CNS, muscle, endoneuro, peripheral nerve Sinusoidal – liver, spleen Fenestrated – glomerulus In the CNS, you have Continuous Capillaries

6) Pass

Have 3 types of transport in the body PTT - Paracellular - Transcellular - Transcytotic-vesicular

7) In the BBB

- No paracellular due to tight junctions - poor transcellular and transcytotic-vesicular You have guards in the CNS – P-glycoproteins - take lipid soluble substances out the brain - energy-dependent transport

8) What does not pass BBB?

BIG guys – plasma proteins & substances attached to them HORNY guys – highly charged TOXIC guys – even if small What does pass BBB? BABY molecules – H2O, O2, CO2 - But, H+ no, He is a Horny guy SWETTY guys – glucose & aminoacids (carrier mediated)

9) BBB vs BCF difference

Where is the tight junction is the ≠ BBB – Blood (endothelial) vs BCB – Choroidal (choroidal epithelial cells)

10) Types of cerebral edema

COVI: Cytotoxic, Osmotic, Vasogenic, Interstitial - vasogenic is considered the MC - doesn’t have a clear mechanism, may be a combination of mechanisms Types Intracellular – cytotoxic & osmotic Extracellular – vasogenic

11) Circumventricular organs

- circumventricular organs are specialized areas of CNS where BBB is modified or broken - all of them are surrounded by 3rd & 4th ventricles - ependymal cells proximal to ventricular areas are modified and their name are tanycyte

12) Micro-structure

- highly vascularized - fenestration of endothelial cells - permeable basement membrane - astrocyte podocyte (foot processes) do not form complete circle EXCEPTION: subcommissural organ has non-fenestrated capillaries

13) Tanycyte

- line the floor of the 3rd ventricle - conduit between CSF and blood

14) Function of circumventricular organs

- chemosensitive organs - allow “sampling” of blood - endocrine feedback and regulation - homeostasis - metabolic regulation - fluid electrolyte balance - detect toxins in blood - CSF circulation

15) "POSSMAN"