Blood supply of the brain (Chapter 6)

Question 1

_____________ arteries provide ~80% of blood supply (cerebrum and diencephalon), _____________ arteries provide the other ~20% (brainstem & cerebellum).

Answer 1

Internal carotid; vertebral

Question 2

What is the general function of the Circle of Willis?

Answer 2

It interconnects the internal carotid and vertebral-basilar systems.
If one artery is occluded, it provides an alternate route.

Question 3

Describe the arteries making up the Circle of Willis, from anterior to posterior.

Answer 3

Anterior cerebral
Anterior communicating
Internal carotid (medial side) / middle cerebral (lateral side)
Posterior communicating
Posterior cerebral
Basilar
Vertebral

Question 4

What are the major territories of the anterior, middle, and posterior cerebral arteries?

Answer 4

ACA: frontal, parietal, midline
MCA: surface regions of F/P/T/O; basal ganglia, limbic regions
PCA: occipital

Question 5

Where do most of the major superficial veins empty into?

Where do most of the major deep veins empty into?

Answer 5

Superior sagittal sinus

Straight sinus

Question 6

List the 3 major deep veins.

Answer 6

Basal vein of Rosenthal
Great vein of Galan
Internal cerebral vein

Question 7

List the 3 major superficial veins.

Answer 7

Superior middle cerebral (runs laterally)
Superior anastomotic vein of Trolard (runs superiorly from SMC)
Inferior anastomotic vein of Labbe (runs inferiorly from SMC)

Question 8

What does fMRI measure and how is the astrocyte-neuron lactate model relevant?

Answer 8

In the astrocyte-neuron lactate model, excitatory glutamate is released by the neuron and binds with receptors in the feet of astrocytes. This causes a release of vasodilators.
fMRI measures localized increases in bloodflow tied to increased neuronal firing.

Question 9

What is the blood-brain barrier?

Answer 9

The BBB is a highly selective semi-permeable membrane that wraps around cerebral capillaries. Tight gaps in epithelial cells allow lipid-soluble and glucose molecules to cross but block other molecules.

Question 10

What are circumventricular organs and what is their purpose?

Answer 10

Circumventricular organs are regions where cerebral capillaries allow free communication between blood and extracellular fluid (“leaky areas”).
- Pineal gland, parts of pituitary and hypothalamus, choroid plexus in 3rd and 4th ventricles
Allows the brainstem to monitor extracellular fluid concentration and blood glucose levels.

Question 11

Define hemorrhagic vs. ischemic stroke.

Answer 11

Hemorrhagic: Rupture of a vessel (usually artery)
Ischemic: Blockage of a vessel due to thrombus or embolus

Question 12

Name some of the most common symptoms of stroke.

Answer 12

• Sudden numbness or weakness of face, arm or leg, especially on one side of the body.
• Sudden confusion, trouble speaking or understanding.
• Sudden trouble seeing in one or both eyes
• Sudden trouble walking, dizziness, loss of balance, or incoordination.
• Sudden severe headache with no known cause.