Blood Supply

Human Neurobiology ANHB 2217

Avinash Bharadwaj

Semester 1, 2006Week 2

Blood Vessels of CNS

Nervous tissue – high metabolic needs One-fiftieth of body weight One-sixth of circulating blood volume One-fifth of oxygen consumption

Extreme sensitivity to reduction or loss Seconds and minutes…!

The nature of arteries to the brain Thin walls Susceptibility to vascular diseases

Cerebrovascular Disease

Narrowing of arteries (Stenosis)

Blocks in arteries “Plaques” and thrombi Emboli

Rupture Weak wall / High Pressure Aneurysm

Cerebrovascular Disease

“Atheromatous change”

Rough surface – clotting of blood (thrombosis)

Clot or other matter coming in from elsewhere – embolus Blood clots dislodged from other parts Fat from fractures

Blocks and Bleeds

Blockage of an artery Transient or total End arteries – no collateral

circulation “Infarct”

Bleeding (Haemorrhage) Damage can be extensive Bleeding outside the brain but

within cranial cavity… pressure

Strokes and transient ischaemic attacks

1

2

3

Main Arterial Channels

Internal carotid

Vertebral(“Vertebro- basilar”)

Arterial Cast

Internal carotid

Vertebral(“Vertebro-basilar”)

Arterial Circle (of Willis)

Vertebral

Basilar

ICA ACA

MCA

PCA

SCA

AICA

PICA

Be careful with abbreviations!

Cortical and central branches

The Arterial Circle

Can compensate for slow blockage

Can equalise pressure

Variable pattern

Compensation is not reliable!

Arteries – Courses

ACA

MCA

PCA

Cerebral Arteries

Branches of middle cerebral artery

Anterior cerebral artery and its branches

Branches of posterior cerebral artery

Arterial Territories

ACA

MCA

PCA

ACA

MCA

PCA

Superolateral surface Medial surface

Think in terms of lobes and (later), functional areasLocalisation an important part of diagnosis.

Cortical and Central…

Cortical Longer, spread over the

surface

Central Short, slender Groups

Anterior and posterior (medial + lateral in each group)

“Perforated substance” Supply deeper structures

including basal nuclei, diencephalon, internal capsule and even midbrain

AM

ALPM

PL

Brainstem and Cerebellum

Vertebrobasilar system

“Cerebellar” arteries Supply cerebellum and parts of brainstem Two inferior (“PICA” and “AICA) One superior Medullary, pontine and mesencephalic

branches

Spinal Arteries

Begin from the vertebral Anterior spinal artery (2 1) Posterior spinal arteries

Reinforced by segmental arteries

Last slide!