Human Neurobiology ANHB 2217 Avinash Bharadwaj Semester 1, 2006 Week 2 Blood Supply Human Neurobiology ANHB 2217 Avinash Bharadwaj Semester 1, 2006 Week 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 Bleeding (Haemorrhage) 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 3 2

Main Arterial Channels Internal carotid Vertebral (“Vertebro- basilar”)

Arterial Cast Internal carotid Vertebral (“Vertebro-basilar”)

Arterial Circle (of Willis) ACA ICA MCA Cortical and central branches PCA Basilar SCA AICA Vertebral PICA Be careful with abbreviations!

The Arterial Circle Can compensate for slow blockage Can equalise pressure Variable pattern Compensation is not reliable!

Arteries – Courses ACA PCA MCA

Cerebral Arteries Branches of middle cerebral artery Anterior cerebral artery and its branches Knowledge of these territories, combined with a knowledge of what areas of cortex do what (a later lecture) can provide the clinician with a good idea of where a blockage has occurred. The striatum has a major role in motor control, damage to the fine arteries here can cause motor problems. Branches of posterior cerebral artery

Arterial Territories ACA ACA MCA PCA PCA MCA Superolateral surface Medial surface Think in terms of lobes and (later), functional areas Localisation an important part of diagnosis.

Cortical and Central… Cortical Central Longer, spread over the surface 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 AL PM 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!