Neurons oxygen supply

The brain has an absolute dependence on the blood for its immediate supply of oxygen and energy substrates. Interruption of oxygen or substrate supply by compromise of pulmonary or cardiovascular function or metabolic factors results in encephalopathy and, if prolonged, neuronal cell death. The brain uses approximately 20% of the total oxygen supply of the body. While glucose remains the primary energy substrate for the brain, alternative substrates maybe used under certain circumstances (see Ch. 31). 

Another condition in which energy stress plays a role in disturbance of neural activity is stroke. In stroke, either haemorrhagic or ischaemic, the oxygen supply to parts of the brain is reduced. Since ATP generation is totally aerobic in neurones, this results in complete failure of ATP generation. 

Blockage of blood supply to part of the brain by a thrombus reduces its oxygen supply and damages neurones in the area, causing a stroke. Similar damage can be caused by a bleed into the nerve tissue. Risk factors for stroke include hypertension, hyperlipidaemia and clotting defects. 

Silver IA, Erecinska M. 1994. Extracellular glucose concentration in mammalian brain Continuous monitoring of changes during increased neuronal activity and upon limitation in oxygen supply in normo-, hypo, and hyperglycemic animals. J Neurosci 14 5068-5076. 

Neuronal function depends on a constant supply of oxygen. Hypoxia, a decrease in oxygen availability, depresses neuronal activity. Interruption of blood flow to the brain for only a few seconds leads to unconsciousness. A prolonged lack of blood flow, which is characteristic of stroke, leads to permanent brain damage in the affected area. 

The brain uses a substantial proportion of body oxygen and there is a generous blood supply to the brain from the carotid and vertebral arteries. Interruption of brain blood flow for more than a very short time causes neuronal damage and ultimately cell death. Cerebral blood flow is normally controlled by autoregulation. 

Energy requirement Neurons require the continuous supply of glucose and oxygen in order to generate the large amount of ATP needed to support various cellular processes... 

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