Cerebral Circulation Flashcards
Two main sources of arterial supply to the brain
internal carotid (from common carotid) vertebral arteries (from subclavian)
vertebral arteries supply
posterior circulation: telencephalon and diencephalon
internal carotid arteries supply
anterior circulation: brainstem, cerebellum, diencephalon, SC, occipital and temporal lobes
Posterior communicating artery (PCOM) comes off of the ________ artery and joints to ________ artery.
internal carotid a. –> posterior cerebral a.
connects anterior circulation to posterior circulation
opthalmic a comes off of the
internal carotid a.
internal carotid a. bifurcates into the
middle cerebral a. (MCA) and anterior cerebral a. (ACA)
________ supplies the medial aspects of the cerebral hemispheres.
ACA
________ connects the 2 anterior cerebral arteries near the entrance to the longitudinal fissure.
ACOMM
_____ supplies almost the entire lateral surface of the hemisphere. (most often implicated in stroke!)
MCA
_____ 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.
Lenticulostriate arteries
MCA
PICA stands for _____; PCA stands for ______
posterior inferior cerebellar artery; posterior cerebral artery (don’t confuse these!)
Each vertebral artery gives off 3 branches:
- posterior spinal artery
- anterior spinal artery
- PICA
The two vertebral arteries come together to form the ______ artery.
basilar a.
Basilar gives off several branches:
AICA, pontine branches, labyrinthine a, superior cerebellar a, posterior cerebellar a.
Basilar ends by branching into 2 of these
PCA (supplies medial temporal and occipital bones)
The circle of willis encircles what two structures?
infundibulum and optic chiasm
The circle of willis connects which systems?
internal carotid and vertebral basilar systems
Ant spinal artery supplies anterior _____ of SC; post. spinal artery supplies posterior _____ of SC.
ant: 2/3
post: 1/3
Circle of willis well developed in what percent of population?
18%
What is a CVA? What are two types of CVAs
interruption of blood flow
- hemorrhagic stroke
- ischemic stroke
Normally there is ____ flow around the circle. Why?
NO FLOW
because pressure of ICA = pressure of PCA
Ischemic stroke is due to blockage of an artery by 2 different causes:
thrombus: clot formed in vessel lumen
embolus: blood clot, plaque, bubbles that travel from somewhere else
Hemorrhagic stroke is due to:
rupture of artery or aneurysm (may bleed into subarachnoid space or brain)
Aneurysm is frequent in which site?
anterior half of circle of willis
How is aneurysm treated?
clipped (requires craniotomy) or coiled (catheterization)
Venous drainage parallels the arteries. Runs from peripheral brain to the _____ sinuses before empyting into the ____.
dural sinuses jugular foramen (where the internal jugular vein originates)
What percent of cardiac output is utilized by the brain?
15%
What percent of oxygen consumption is utilized by the brain?
25%
Blood brain barrier fxn?
controlled movement of general body extracellular fluid to the extracellular fluid of the brain
The true blood brain barrier is between what structures?
capillaries in the brain and brain tissue
What are the three components of blood brain barrier?
- CSF-blood barrier (choroid plexus)
- Arachnoid barrier (arachnoid villi/superior sagittal sinus)
- True blood-brain barrier
Major pro and con to blood brain barrier?
+: brain is immunologicaly privileged; microorganisms can’t enter
-: blocks antibiotics and drugs (i.e. dopamine)
The selective barrier to the brain allows what substances to enter?
diffusion: lipid-soluable (i.e. alcohol), CO2, O2, water
mediated transport: glucose, amino acids
What are the 2 general areas of compromised blood brain barrier?
- areas of secretion: pineal gland, posterior pituitary
2. areas where brain monitors extracellular fluid: hypothalamus
What are some conditions in which blood brain barrier is compromised?
tumors with fenestrated (leaky) capillaries; brain injury/acute HTN; ischemia; CNS infection
