Blood supply of the brain
In this lesson, you’ll learn how the brain is supplied with blood and how the blood–brain barrier helps protect brain tissue by regulating what can pass from the bloodstream into the brain.
1) Start with this video:
2) Then, read this article: Know Your Brain - Blood-Brain Barrier
3) Next, watch this video to reinforce what you just read:
4) Finally, answer these questions to test your understanding:
1. Which of the following arteries is part of the circle of Willis?
- A. posterior inferior cerebellar artery
- B. anterior cerebral artery
- C. anterior choroidal artery
- D. middle cerebral artery
Show Answer
Correct answer: B
The anterior cerebral, internal carotid, and posterior cerebral arteries on both sides of the brain are interconnected by the anterior and posterior communicating arteries, forming a ring-like structure known as the circle of Willis. This interconnection can allow blood flow to continue if a major vessel is blocked on one side of the brain.
2. Which artery connects the left and right anterior cerebral arteries?
- A. basilar artery
- B. middle cerebral artery
- C. posterior inferior cerebellar artery
- D. anterior communicating artery
Show Answer
Correct answer: D
The anterior cerebral arteries supply the medial frontal and parietal lobes, and they are connected by the anterior communicating artery.
3. Which structural feature of endothelial cells in brain capillaries most directly prevents substances from moving from the bloodstream into the brain at the blood–brain barrier?
- A. large pores in endothelial cells
- B. tight junctions between endothelial cells
- C. aquaporin channels in endothelial cell membranes
- D. voltage-gated ion channels on endothelial cells
Show Answer
Correct answer: B
It is thought that the central components of the structure of the blood-brain barrier are the tight junctions of endothelial cells, the cells that make up the interior surface of blood vessels. The endothelial cells that make up the blood-brain barrier are fused tightly together to form tight junctions that restrict diffusion across the blood vessel lining.
4. These glial cells provide metabolic support to neurons and help maintain the blood-brain barrier:
- A. oligodendrocytes
- B. astrocytes
- C. ependymal cells
- D. microglia
Show Answer
Correct answer: B
Astrocytes are star-shaped glial cells with many functions, which include providing nutrient support to neurons, helping repair damage to nervous system tissue, regulating communication between neurons, and maintaining the blood-brain-barrier, which keeps potentially toxic substances in the blood from entering the brain.
5. The blood-brain barrier helps to keep unwanted substances from passing out of the cerebral bloodstream and into the brain. Which of the following characteristics would you likely see in a substance that is able to cross the blood-brain barrier?
- A. it is a large molecule
- B. it is a complex carbohydrate
- C. it is soluble in lipids
- D. it is an antibiotic drug
Show Answer
Correct answer: C
The blood-brain barrier is a complex that surrounds most of the blood vessels in the brain. It acts as a barrier between the bloodstream and the extracellular space of the brain, allowing only certain substances like water, oxygen, and small lipid-soluble substances to easily cross from the blood into the brain.
