Blood Supply of the CNS Flashcards
Describe the mechanism of regulation of cerebral blood flow:
neurovascular unit = system that regulated blood flow and where it goes, what goes in/out,..
- Autoregulation, through arterial and smooth muscle cells.
- Metabolic, increased neuronal activity, increases glutamate, which activate astrocyte end feet receptors, thus vasodilator factors released at the vessel.
- Neural control- cerebral vessels are innervated by autonomic fibers.
List the brain “barriers”
- Blood-Brain Barrier
- Blood-CSF barrier
(chorodial epithelium) - Arachnoid barrier
- Blood-Spinal Cord, blood-nerve, blood-retinal, blood-labyrinth barriers.
Describe the function of the BBB and of its components:
- most important component of the neurovascular unit
- separates blood circulating with extra cellular fluid in CNS.
- formed by tight junctions with the help of astrocytes (pericytes and neuronal processes)
-restricts ionic/fluid movements, supplies essential nutrients, mediates efflux of waste or toxic products.
Describe circumventricular organs and their role:
Unit of neurons, glial, ependymal cells, leptomeningeal and vascular elements, around the 3rd and 4th ventricles that aid in the communication between the blood, brain parenchyma and CSF.
Lack a BBB, thus critical role in balance, regulation in ions, metabolism and immuno components.
Specialized cells called Tanycytes overlie CVO, and acts as a barrier between the organ and ventricular CSF.
Two types: sensory and secretory:
Sensory- area postrema
Secretory- p. pituitary
Describe the drainage pattern of cerebral veins (deep and superficial groups)
Superficial veins drain into the superior sagittal sinus which trains into the Confluence of Sinus …
Deep veins drain into the ICV –> Great Vein of Galen –> Straight –> Confluence of Sinus
Confluence of Sinus then trains into the Transverse Sinus, which trains into the Internal Jugular Vein.
Describe the difference between subdural and epidural hematoma:
Epidural hematoma: caused by laceration of the middle meningeal ARTERY. Dura is being pushed away from the skull, as blood is building up between the skull and the dura; seen as a biconvex lens in CT. Could cause a herniation as the brain is being pushed.
Subdural hematoma: Usually due to hemorrhage of bridging veins, between dura and arachnoid. Leads to a collection of old blood. Sen as a crescent shape in CT.
What vascular territory is mostly affected by strokes?
anterior circulation, delivered by internal cerebral artery
Describe cerebral circulation:
Two major components:
- Anterior component: delivered by the internal cerebral artery that will bifurcate into the anterior and middle cerebral arteries. Perfuse most of the cerebrum.
- Vertebrobasilar system: delivered by the fusion of two vertebral arteries, to form the basilar artery. The basilar artery then bifurcates into posterior cerebral arteries. Along the way, there is PICA, AICA, SCA.
What are ganglionic arteries?
Arteries around the base of the brain, that give rise to small perforating/ ganglionic arteries.
Perforate very specific areas of the brain.
Clinically relevant, in people with HBP- if pressure gets transmitted to these tiny artery, these arteries could be damaged and cause tiny strokes, that can eventually lead to dementia.
What are perforated substances?
Anterior and posterior perforated substance are visible entry points of perforating arteries on base of the brain.
Come off of Circle of Willis
Describe the Circle of Willis:
Interconnects the anterior and posterior circulations.
Posterior Cerebral Arteries to Posterior Comm. Arteries, ICA, MCA, ACA and connecting with the other side with anterior communicating artery.
Describe HOW the BBB functions:
It is a capillary of endothelial cells, that have astrocytes + other stuff that ADJUST the barrier depending on what the cell needs.
Astrocytes communicates with neurons and sends a message to the endothelia cells; neurons can control what comes in and out (neurons can influence the astrocyte).
