The overall physiologic state of the organism: healthy or impaired, resting or stressed, conditioned, aged, overall functional adequacy. Organ level function: Blood flow, oxygen consumption, utilization of substrates and production of metabolites, hormones, etc., energy balance, adequacy to maintain normal function over a range of conditions of the organism. For the heart this level would include stroke output, heart rate, pressure output, work, energy consumption, substrate consumption. flows. Relation to organism: neural humoral, mechanical feedback. Intraorgan regional variations: Differences in functions such as regional flows, substrate uptake, metabolism, work (internal, external) For the heart: atria versus ventricles, contractility, heart rhythm and rate, contractile tension, myocardial deformation and relaxation, propagation of excitation Tissue and cells: cellular physiologic and biochemical functions, mechanical and physicochemical features, composition and anatomic measures, blood-tissue exchange, metabolic fluxes, intercellular communication, traffic along biochemical pathways, all of which contribute to stabilizing the volumes and the concentrations in cells and in intercellular spaces. Subcellular constituent and protein level, the basic biophysical, biochemical levels of subcellular function: Pumps, channels, enzymes, receptors: activation, inhibition, rates, competition, regulation. Molecular behavioral level: Protein conformational states: site accessibility, channeling, sensitivity to pH, etc., molecular abnormalities.
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