Oxygen supply reduction

The major drawback of these models, however, is their lack of a clear reference between model components and constituent parts of the biological system (e.g. structures like ion channels, transporter proteins, receptors, etc.). These models, therefore, do not permit the simulation of patho-physiological detail, such as the series of events that follows a reduction in oxygen supply to the cardiac muscle and, ultimately, causes serious disturbances in heart rhythm. 

The same applies to pathologically-disturbed function. A simulated reduction in coronary blood flow (heart attack) would lead to reduced oxygen supply to the cells in the virtual heart, which would reduce efficiency of cardiac contraction and possibly give rise to heart rhythm disturbances. Ventricular pressure development would be compromised, as would the blood supply to all organs of the body, including the heart. All these implications can be studied in a virtual heart. 

Nifedipin causes relaxation of smooth musculature, dilation of coronary and peripheral arteries, and reduction of peripheral resistance and arterial blood pressure, and enhances oxygen supply to the heart. 

Schwertmann, 1993). Such soils are characterized by a hydraulic conductivity somewhere in the profile which is too low to cope with the high rainfall, so that all pores will be filled with water for certain periods of time (see above). In this case, the oxygen supply is limited by the low level of O2 dissolved in the soil water (46 mg O2 at 25 °C) and reduction of Mn-oxides, nitrate and Fe oxides sets in. Soils containing Fe oxides are, therefore, redox-buffered (poised). The redox titration curve (Fig. 16.14) of a soil with 23 g kg Fe as Fe oxides shows buffering at two different pe -1- pH levels, one at ca. 11 and another at ca. 9, which indicate the presence of a more reducible (e. g. ferrihydrite) and a less reducible (e. g. goethite) Fe oxide, respectively, in accordance with their different solubilities (see Chap. 9). 

All of the aforementioned beneficial effects of the /3-blockers are caused by the blockade of /3i-adrenoceptors. The beneficial effect of /3-blockers in the treatment of angina is largely caused by the reduction of heart rate and the concomitant decrease in myocardial oxygen consumption, thus improving the imbalance between oxygen supply and consumption which underlies myocardial ischaemia. 

Dihydropyridine-CA reduction of cardiac afterload reduction of coronary spasm and coronary vasodilatation improved myocardial oxygen supply. 

Hypoxia. Reduction of oxygen supply to tissue below physiological levels despite adequate perfusion of the tissue by blood. Hypoventilation. Underventilation reduced alveolar ventilation in relation to the oxygen consumption. 

Carbon monoxide Interferes with oxygen transport by blood, resulting in the reduction of oxygen supply to the heart (chronic anoxia), heart and brain damage, impaired perception... 

Amperometric transducers measure the current (flux of electrons) caused by oxidation or reduction of the species of interest when a voltage is applied between the working and the reference electrode. Often, oxygen serves as electron acceptor but interferences have encouraged development of new methods to avoid this, e.g. controlled oxygen supply and the application of mediators, such as ferrocene, e.g. [169]. Other determinations focus on the... 

Occlusion of the hepatic artery is responsible for a 50% reduction in oxygen supply. Even if an unimpaired oxygen supply via the portal vein is guaranteed, arterial occlusion usually causes ischaemic infarction. The clinical and morphological pictures are characterized (1.) by the speed with which an occlusion develops and (2.) by the presence of variants that can be used as a bypass or of collaterals that have already been established in gradual vascular occlusion. This results in a broad clinical spectrum, which may range from a symptom-free condition to liver hypoxia, including infarction up to hepatic coma. 

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