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Fig. 6. Energy budgets break down the energetic costs of neural processing into its
constituent components. (A) The energy consumption of the various neuronal
components that contribute to the energy consumption of a single action
potential (AP) and the events at a glutamateric synapse triggered by it in rat
cortex. The AP itself consumes more than 50% of the total energy consumed.
Other processes that also consume energy include the activation of NMDA,
non-NMDA and metabotropic glutamate post-synaptic receptors, the recycling of
glutamate and the entry of presynaptic Ca2+ ions that trigger
vesicle release. Many of these processes can be linked to the activity of the
sodium–potassium exchanger. (B) The energy consumption of various neural
components within a rat olfactory glomerulus with one sniff per second as a
function of odour concentration. The contributions of different components
change with increasing odour concentration. The resting potential is the
dominant cost at low odour concentrations but axonal action potentials, the
activation of post-synaptic receptors and dendritic back-propagating action
potentials consume substantial amounts of energy at higher concentrations.
Adapted from Attwell and Laughlin (Attwell
and Laughlin, 2001) and Nawroth et al.
(Nawroth et al., 2007).
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