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Flashcards in Blood Supply of the CNS Deck (12)
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1
Q

Describe the mechanism of regulation of cerebral blood flow:

A

neurovascular unit = system that regulated blood flow and where it goes, what goes in/out,..

  1. Autoregulation, through arterial and smooth muscle cells.
  2. Metabolic, increased neuronal activity, increases glutamate, which activate astrocyte end feet receptors, thus vasodilator factors released at the vessel.
  3. Neural control- cerebral vessels are innervated by autonomic fibers.
2
Q

List the brain “barriers”

A
  1. Blood-Brain Barrier
  2. Blood-CSF barrier
    (chorodial epithelium)
  3. Arachnoid barrier
  4. Blood-Spinal Cord, blood-nerve, blood-retinal, blood-labyrinth barriers.
3
Q

Describe the function of the BBB and of its components:

A
  • 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.

4
Q

Describe circumventricular organs and their role:

A

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

5
Q

Describe the drainage pattern of cerebral veins (deep and superficial groups)

A

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.

6
Q

Describe the difference between subdural and epidural hematoma:

A

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.

7
Q

What vascular territory is mostly affected by strokes?

A

anterior circulation, delivered by internal cerebral artery

8
Q

Describe cerebral circulation:

A

Two major components:

  1. Anterior component: delivered by the internal cerebral artery that will bifurcate into the anterior and middle cerebral arteries. Perfuse most of the cerebrum.
  2. 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.
9
Q

What are ganglionic arteries?

A

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.

10
Q

What are perforated substances?

A

Anterior and posterior perforated substance are visible entry points of perforating arteries on base of the brain.

Come off of Circle of Willis

11
Q

Describe the Circle of Willis:

A

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.

12
Q

Describe HOW the BBB functions:

A

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).