Control of blood flow in differing vascular beds

Flow to cardiac muscle can increase 4-5x when cardiac output increases

A secure O2 supply to coronary muscle

Large increases in flow

Very large a-vO2 difference

Right coronary artery Left coronary artery Circumflex artery Left anterior descending branch Posterior descending artery

Arterial pressure > venous pressure Pressure inside > Pressure outside

During diastole

Aortic pressure during diastole

Reduces time Diastole shortened

During systole

Coronary arteries exhibit myogenic autoregulation in pressure range 60-180mmHg Some sympathetic control but overridden by local control Metabolic hyperaemia is the dominant form of regulation

Decreased coronary flow due to narrowed coronary arteries Results in pain during exercise

Loss of consciousness Neuronal damage

Ensuring O2 supply to brain tissue is maintained

The name given to the connected arteries of the brain

Vertebral arteries Basilar artery Posterior cerebral artery Posterior communicating artery Carotid arteries Middle cerebral artery Anterior communicating artery Anterior cerebral artery

Short arterioles Dense capillary network Relatively high vascular resistance Cerebral perfusion maintained if carotid artery obstructed

3000-4000/mm2

Cerebral capillaries form tight junctions so there is no bulk flow No vesicular transport Protects neurones Maintains environment Responsible for long lasting effects of heroine

15% of cardiac output

Regulating other organs Peripheral vasoconstriction

A change in blood pressure is met by a change in resistance to maintain perfusion

~60 - ~170 mmHg

CO2