Lecture Webcasts - Blood Brain Barrier

Question 1

Define the blood brain barrier

Answer 1

Endothelial cells lining the microvasculature of the brain to form a barrier between the circulation and the interstitial fluid.

Question 2

What is the function of the blood brain barrier?

Answer 2

Helps maintain a stable microenvironment for the proper functioning of neurons within the CNS.

Question 3

What is the difference between systemic and brain capillaries?

Answer 3

Systemic: Gaps (fenestra) between the cytoplasm of adjacent cells. Numerous pinocytotic vesicles that help movement of things from lumen to EC space.

Brain: Linked by tight junctions and have few pinocytotic vesicles.

Question 4

The BBB is a _____ barrier. Why is this?

Answer 4

physical.

Because of complex tight junctions that restrict the movement of things to intracellular route and establish endothelial polarity.

Question 5

The lack of pinocytotic vesicles in the BBB indicates what?

Answer 5

The reduced transport through the endothelial cells.

Question 6

Within the brain, capillary endothelial cells are surrounded by what?

Answer 6

Basal lamina, pericytes, and astrocyte foot processes.

Question 7

What are pericytes?

Answer 7

Cells with smooth muscle like properties

Question 8

What is the location of astrocyties in the BBB?

Answer 8

They cover the abluminal surface (faces away from the capillary lumen).

Provide cellular link to neurons.

Question 9

What substances can move through the BBB? How do they do it?

Answer 9

Lipid soluble agents- diffuse membrane of the cells. (CNS drugs enter the brain this way)

Water soluble agents are limited in their paracellular movement.

Glucose, aas,

Question 10

How do water soluble agents pass through the BBB?

Answer 10

They are very limited in their movement, but can move through to some extent paracellularly.

Question 11

How do lipophillic molecules move through the BBB?

Answer 11

They can diffuse through the lipid membrane of the cells (transcellular).

Ethanol and barbiturates move this way.

Most CNS drugs enter the brain this way.

Question 12

What substances can move through the BBB through endothelial cell transporters?

Answer 12

Nutrients: glucose, amino acids, nucleosides. (glucose cannot be moved against concentration gradient).

Also gets rid of waste.

Question 13

What medications get to the brain via transport proteins?

Answer 13

L-dopa used to treat parkinsons, and chemotherapy agents.

Question 14

How do insulin and transferrin get to the brain?

Answer 14

Via receptor-mediated endocytosis.

Question 15

How do plasma proteins such as albumin get to the brain?

Answer 15

If surrounded by cations they can be taken up by the cell via absorptive transcytosis.

Question 16

What is the functions of the enzymes of the BBB?

Answer 16

They help regulate the composition of the brain interstitial fluid.

Question 17

What are three barrier functions of astrocytes (glial cells)?

Answer 17

Regulate tight junctions (physical barrier), influence expression and polarization of transporters (transport barrier), and influence expression of enzyme systems (metabolic barrier)

Question 18

What are some pathologies that impact the BBB?

Answer 18

Stroke, trauma, infection/inflammation, MS, HIV, Alzheimer’s, Parkinson’s, epilepsy, tumors, and pain

Question 19

What areas of the brain normally lack the BBB?

Answer 19

The circumventricular organs:

Pineal gland
subfornical organ
vascular organ of the laminal terminais
median eminence
area postrema.