blood brain barrier

what is the blood brain barrier?

a functional barrier which provides tight control of the substances passing into and out of the brain

what are the functions of the blood brain barrier? (3)

- manage microenvironment

- regulates entry of nutrients + exits of waste

- regulates ions + fluid movement

what is the blood brain barrier between?

capillaries + neurones of the brain

what are the 3 main structures of the blood brain barrier?

1) endothelium of capillary

2) basement membrane/basal lamina

3) astrocytes

what lie between the endothelial cells?

tight junctions

what are the importance of the tight junctions?

limit movement in and out of capillaries

what else can the endothelial cells do?

release inactivating enzymes

what 2 cell types are found in the basal lamina?

- pericytes

- macrophages

where are pericytes found?

running along + around capillary endothelial cells

what is the function of pericytes?

chemical sensors of the bloodstream to restrict what comes in and out of the capillaries

how do pericytes manage substance movement in and out of the capillaries?

contract to make the capillaries narrower and affect blood flow

how else can pericytes affect substance movement from capillaries?

can make new vascular tissue

where are the macrophages found?

surrounding pericytes

what do the macrophages do?

protect brain parenchyma by phagocytosing foreign pathogens

what is an important features of the astrocytes?

they have end-feet which wrap around the capillaries

what is the function of the astrocytes?

- control the rest of the blood brain barrier

- limits the substances which can pass through themselves

what are 3 areas that do not contain the blood brain barrier?

- vomiting centre

- osmoreceptors

- neurohypophysis (posterior pituitary)

why does the neurohypophysis not have a blood brain barrier?

oxytocin and ADH are released directly into the bloodstream

why does the posterior pituitary gland need direct contact with the bloodstream?

to release hormones directly into the bloodstream

what substances can enter the blood brain barrier? (9)

- amino acids

- glucose

- vitamin k

- vitamin d

- Na+

- K+

- lipid soluble substances

- CO2

- O2

can H+ pass through BBB?

no