Lecture 7: The Cerebral Circulation & Neuronal Environment Flashcards
The blood supply of the brain and spinal cord arises from what structure?
- Two sets of branches from the dorsal aorta
1. Subclavian arteries
2. Common carotid arteries
Subclavian arteries gives rise to what?
Vertebral arteries
What artery branches off the common carotid arteries?
Internal carotid arteries and external carotid arteries
Loss of blood supply to the brain leads to?
Death of neurons within 3-5 mins (Neurons have high metabolic rate and high demand for oxygen)
Vertebral arteries that supply the spinal cord give rise to what arteries?
- Branches that merge into the anterior spinal artery (single artery in anterior/ventral surface)
- Gives rise to the paired posterior spinal artery (paired arteries in dorsal/posterior surface)
What are the supplementary arteries of the spinal cord?
- Medually arteries ( short 10-12 segmental arteries that join the anterior/posterior spinal artery)
- They arise from the segmented branches of the aorta
An obstruction/ damage (surgery) of the medullary artery could lead to loss of blood supply to the spinal cord. What function would be lost?
- Posterior blood supply -loss of sensory function
- Anterior blood supply- loss of motor function
What are the 2 major branches of the internal carotid artery (ICA)?
- Anterior cerebral artery (ACA)
- Middle cerebral artery (MCA)
Basilar artery is formed by what?
basilar a. (midline) is formed by right and left vertebral a
____ joins the blood supply from the internal carotids in an arterial ring structure called _____
basilar a, Circle of Willis
What does the circle of willis interconnect?
Interconnects the internal carotid and vertebral circulation
An anastomosis helps assure cortical circulation if one system slowly becomes occluded.
How does the Circle of Willis interconnect the internal carotid and vertebral circulation
Posterior cerebral a. < - > posterior communicating a. < - >middle cerebral/internal carotid a. < - > anterior cerebral a < - > anterior communicating a.
What branches are part of the Circle of Willis?
ACA and MCA (branches of the ICA) and PCA
ACA-Anterior Cerebral aa.
MCA-Middle Cerebral aa.
PCA- Posterior Cerebral aa. ( terminal of basilar a.)
If one of the major arteries becomes occluded, the Circle of Willis secures that all regions of the brain are still able to receive the blood by which structures?
Two small bridging communicating arteries:
1. Anterior (Ant) communicating a
2. Posterior (Post) communicating a
What is the blood supply to the cerebellum (3)?
Vertebral circulation
SCA – supplies the superior portion of the cerebellum
AICA – supplies the lateral portion of the cerebellum
PICA – supplies the inferior portion of the cerebellum
superior cerebellar artery
anterior inferior cerbellar artery-
post inferior cerebellar artery
What is the blood supply to the midbrain?
part of brainstem
- Posterior cerebral artery (terminal branches off vertebral artery)
- Superior cerebellar artery
What is the blood supply to the pons?
part of the brainstem
- Superior cerebellar artery
- Basilar artery
- Anterior inferior cerebellar artery (AICA)
AICA is a branch of the basilar artery to the brainstem
What is the blood supply to the medulla?
part of the brainstem
- Anterior inferior cerebellar artery (AICA)
- Posterior inferior cerebellar artery (PICA)
- Vertebral arteries
- Anterior and posterior spinal aa
AICA and PICA and branches of the basilar artery to the brainstem
Why is it important to discuss the blood supply to various regions of the brain?
A compromised blood supply to the brain results in the “Structure Damage/Deficit” in the brain (affects the Somatosensory System)
Anterior circulation to the forebrain is formed by what two arteries?
anterior cerebral (ACA)
middle cerebral (MCA)
braches off ICA
Posterior circulation to the posterior cerebral cortex, thalamus, and the brainstem is formed by what arteries?
- posterior cerebral (PCA )
- basilar
- vertebral
What are the deep penetration cerebral arteries?
lenticulostriate arteries
Branches of ____ and ____ supply blood to the cortex and to the deep structures.
ACA, MCA
Where do the lenticulostriate arteries branches off of and what does it supply?
The lenticulostriate arteries branches off MCA supply blood to the deep structures such as basal ganglia, internal capsule, and hippocampus.
A high incidence of damage of deep penetrating cerebral arteries in patients with what?
chronic hypertension and in the elderly: rupture (intracerebral hemorrhage) or occlusion (lacunar infarct).
Deep Penetrating Cerebral arteries can also be called what?
End arteries which supply regions without significant collateral blood supply. Therefore, their occlusion results in stroke syndromes.
True or False: The size of the infarct ranges from small, (lacunes) to large areas in brain
True
note that lacuna strokes can go unoticed but can cause death
Lacunae strokes are occlusions of what?
Lenticulostrate arteries
What happens to the brain cells after a lacunar stroke?
Within a few months of the infarction, the necrotic brain cells are reabsorbed by macrophages, leaving a small cavity a “lake” or “lacune.” The cells distal to the occlusion die.
The brain uses ____ of normal cardiac output and ____ of body’s O2 consumption
15%, 25%
The overall cereberal blood flow rate is ____ but due to neural activity blood flow ____ in active areas of the brain during various mental activities.
constant, increases
The ratio of ____ in particular regions of the brain increases due to increased regional demand for oxygen.
hemoglobin to deoxyhemoglobin
What is an aneurysm?
balloon-like swelling of arterial wall near bifurcation
can break can cause bleeding and cause obstruction in blood flow
The venous drainage exits the skull through what vessel(s)?
Venous blood drains from the brain through superficial and deep veins into the dural sinuses (Superior Sagittal Sinus), which then drain into the internal jugular (IJ) vein.
What makes up the cerebral microvasculature?
Microvasculature: Deep Penetrating Cerebral Arteries and Capillaries
- basal lamina of blood vessels: borderlines b/w blood vessels and what’s outside
- blood-brain barrier (BBB) of capillaries: connection b/w cells w/in BBB
What is the Virchow-Robin Space (perivascular space)?
It’s a Perivascular subpial space around large blood vessels in the brain. NOT around capillaries
Where does the Virchow-Robin Space (perivascular space) end?
Space stops at the capillary level (stops where capillary starts)
They surround and follow the path of penetrating cortical arterioles e.g. Lenticulostriate aa. (not around capillaries).
What is the clinical significance of VRS?
VRS has a tendency to dilate so you can identify enlarged VRS which have been associated with age, dementia and incidental inflammatory white matter lesions e.g., in multiple sclerosis.