Cerebral Circulation

Question 1

Two main sources of arterial supply to the brain

Answer 1

internal carotid (from common carotid)
vertebral arteries (from subclavian)

Question 2

vertebral arteries supply

Answer 2

posterior circulation: telencephalon and diencephalon

Question 3

internal carotid arteries supply

Answer 3

anterior circulation: brainstem, cerebellum, diencephalon, SC, occipital and temporal lobes

Question 4

Posterior communicating artery (PCOM) comes off of the ________ artery and joints to ________ artery.

Answer 4

internal carotid a. –> posterior cerebral a.

connects anterior circulation to posterior circulation

Question 5

opthalmic a comes off of the

Answer 5

internal carotid a.

Question 6

internal carotid a. bifurcates into the

Answer 6

middle cerebral a. (MCA) and anterior cerebral a. (ACA)

Question 7

________ supplies the medial aspects of the cerebral hemispheres.

Answer 7

ACA

Question 8

________ connects the 2 anterior cerebral arteries near the entrance to the longitudinal fissure.

Answer 8

ACOMM

Question 9

_____ supplies almost the entire lateral surface of the hemisphere. (most often implicated in stroke!)

Answer 9

MCA

Question 10

_____ arteries are central branches off the ______ that supply the deep structures. They are important clinically due to their contribution to stroke. They are prone to hemorrhage bc they have thin walls.

Answer 10

Lenticulostriate arteries

MCA

Question 11

PICA stands for _____; PCA stands for ______

Answer 11

posterior inferior cerebellar artery; posterior cerebral artery (don’t confuse these!)

Question 12

Each vertebral artery gives off 3 branches:

Answer 12

1. posterior spinal artery
2. anterior spinal artery
3. PICA

Question 13

The two vertebral arteries come together to form the ______ artery.

Answer 13

basilar a.

Question 14

Basilar gives off several branches:

Answer 14

AICA, pontine branches, labyrinthine a, superior cerebellar a, posterior cerebellar a.

Question 15

Basilar ends by branching into 2 of these

Answer 15

PCA (supplies medial temporal and occipital bones)

Question 16

The circle of willis encircles what two structures?

Answer 16

infundibulum and optic chiasm

Question 17

The circle of willis connects which systems?

Answer 17

internal carotid and vertebral basilar systems

Question 18

Ant spinal artery supplies anterior _____ of SC; post. spinal artery supplies posterior _____ of SC.

Answer 18

ant: 2/3
post: 1/3

Question 19

Circle of willis well developed in what percent of population?

Answer 19

18%

Question 20

What is a CVA? What are two types of CVAs

Answer 20

interruption of blood flow

1. hemorrhagic stroke
2. ischemic stroke

Question 21

Normally there is ____ flow around the circle. Why?

Answer 21

NO FLOW

because pressure of ICA = pressure of PCA

Question 22

Ischemic stroke is due to blockage of an artery by 2 different causes:

Answer 22

thrombus: clot formed in vessel lumen
embolus: blood clot, plaque, bubbles that travel from somewhere else

Question 23

Hemorrhagic stroke is due to:

Answer 23

rupture of artery or aneurysm (may bleed into subarachnoid space or brain)

Question 24

Aneurysm is frequent in which site?

Answer 24

anterior half of circle of willis

Question 25

How is aneurysm treated?

Answer 25

clipped (requires craniotomy) or coiled (catheterization)

Question 26

Venous drainage parallels the arteries. Runs from peripheral brain to the _____ sinuses before empyting into the ____.

Answer 26

``` dural sinuses jugular foramen (where the internal jugular vein originates) ```

Question 27

What percent of cardiac output is utilized by the brain?

Answer 27

15%

Question 28

What percent of oxygen consumption is utilized by the brain?

Answer 28

25%

Question 29

Blood brain barrier fxn?

Answer 29

controlled movement of general body extracellular fluid to the extracellular fluid of the brain

Question 30

The true blood brain barrier is between what structures?

Answer 30

capillaries in the brain and brain tissue

Question 31

What are the three components of blood brain barrier?

Answer 31

1. CSF-blood barrier (choroid plexus) 2. Arachnoid barrier (arachnoid villi/superior sagittal sinus) 3. True blood-brain barrier

Question 32

Major pro and con to blood brain barrier?

Answer 32

+: brain is immunologicaly privileged; microorganisms can't enter -: blocks antibiotics and drugs (i.e. dopamine)

Question 33

The selective barrier to the brain allows what substances to enter?

Answer 33

diffusion: lipid-soluable (i.e. alcohol), CO2, O2, water | mediated transport: glucose, amino acids

Question 34

What are the 2 general areas of compromised blood brain barrier?

Answer 34

1. areas of secretion: pineal gland, posterior pituitary | 2. areas where brain monitors extracellular fluid: hypothalamus

Question 35

What are some conditions in which blood brain barrier is compromised?

Answer 35

tumors with fenestrated (leaky) capillaries; brain injury/acute HTN; ischemia; CNS infection