the brain's energy consumption
darush at pacbell.net
Tue Apr 29 14:18:07 EST 1997
John E. Anderson wrote:
> Does anyone have a list of what brain processes use all this
> energy? Does maintaining the ionic gradient across membranes consume
> most of it? What proportion is used by processes that reorganize or
> change the weights of synaptic connections?
> John E. Anderson
> jander at unf.edu
Under resting conditions, the metabolism of the brain is about 7.5
times the average metabolism of the rest of the body. Most of this
excess metabolism of the brain occurs in the neurons not the glial
supportive tissues. The major need for metabolism in the neurons is to
pump ions through their membranes, mainly to transport sodium and
calcium ions to the outside of the neuronal membrane and potassium and
chloride ions to the interior (Na/K pump). . Therefore, during excessive
brain activity, neuronal metabolism can increase several fold. Also the
brain is not capable of much anaerobic metabolism because the amount of
glycogen stored in the neurons is slight, so that anaerobic breakdown of
glycogen cannot supply much energy. The stores of oxygen in brain
tissues are also slight.Therefore, most neuronal activity depends on
second-by-second delivery of glucose and oxygen from the blood.
Processes that change the the structure and organization of the synaptic
connections use up a fraction of the energy the brain receives.
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