The Human Brain : From Neurone to Nervous System

CEREBRAL CIRCULATION


  1. The rate of metabolism of the brain is amongst the highest of all organs in the body. Aerobic metabolism provides for all the essential brain functions, and a good supply of oxygen is essential for normal brain function. The arterial blood supply to the brain is the source of oxygen and glucose, and if the blood supply is compromised (ischaemia), then brain tissue can be destroyed.

  2. The Monro-Kellie Doctrine describes the fact that the volume of the skull is constant and the consquences of intracranial tumours or haematomas on intracranial pressure.

  3. Blood flow to the brain is fairly constant over a wide range of arterial pressures, a consequence of Autoregulation.

  4. Blood flow to the brain is not evenly distributed, but is actively directed to highly active sites in the brain. This redisribution of blood flow according to neuronal needs can be analysed using fNMR and PET scanning.

  5. Increased local blood flow is partly the result of accumulation of carbon dioxide in active tissues; carbon dioxide is a powerful vasodilator in the cerebral circulation. There is also evidence that astrocytes can influence local blood flow through the release of vasoactive compounds.

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