Physiological systems

The concentration of salt in physiological systems is on the order of 150 mM, which corresponds to approximately 350 water molecules for each cation-anion pair. Eor this reason, investigations of salt effects in biological systems using detailed atomic models and molecular dynamic simulations become rapidly prohibitive, and mean-field treatments based on continuum electrostatics are advantageous. Such approximations, which were pioneered by Debye and Huckel [11], are valid at moderately low ionic concentration when core-core interactions between the mobile ions can be neglected. Briefly, the spatial density throughout the solvent is assumed to depend only on the local electrostatic poten-... 

Antagonist, a molecule that interferes with the interaction of an agonist and a receptor protein or a molecule that blocks the constitutive elevated basal response of a physiological system. 

Although blood pressure control follows Ohm s law and seems to be simple, it underlies a complex circuit of interrelated systems. Hence, numerous physiologic systems that have pleiotropic effects and interact in complex fashion have been found to modulate blood pressure. Because of their number and complexity it is beyond the scope of the current account to cover all mechanisms and feedback circuits involved in blood pressure control. Rather, an overview of the clinically most relevant ones is presented. These systems include the heart, the blood vessels, the extracellular volume, the kidneys, the nervous system, a variety of humoral factors, and molecular events at the cellular level. They are intertwined to maintain adequate tissue perfusion and nutrition. Normal blood pressure control can be related to cardiac output and the total peripheral resistance. The stroke volume and the heart rate determine cardiac output. Each cycle of cardiac contraction propels a bolus of about 70 ml blood into the systemic arterial system. As one example of the interaction of these multiple systems, the stroke volume is dependent in part on intravascular volume regulated by the kidneys as well as on myocardial contractility. The latter is, in turn, a complex function involving sympathetic and parasympathetic control of heart rate intrinsic activity of the cardiac conduction system complex membrane transport and cellular events requiring influx of calcium, which lead to myocardial fibre shortening and relaxation and affects the humoral substances (e.g., catecholamines) in stimulation heart rate and myocardial fibre tension. 

A basic premise in receptor pharmacology is that all drugs have affinity for receptors (the chemical property that unites the dmg with the receptor), and some drugs have efficacy, the chemical property that causes the receptor to change its behavior toward its host cell. Drugs that have efficacy can produce concentration-dependent responses in physiological systems, characterized by a concentration-response curve (also often referred to as a dose-response cuive). 

Another example of where the setpoint of the physiological system can change the observed behavior of drugs is the absence of direct effects of inverse agonists in nonconstitutively active receptor systems. 

Most known cannabimimetics today have very broad effects on organ systems, several of which are still not completely delineated. The ubiquitous pharmacology of cannabimimetics is one of the reasons for the failure, thus far, of the clinical application of these drugs to reach its full potential. The sections that follow summarize the effects of cannabinergics on the various physiological systems and the possible therapeutic uses that may arise from these biological activities. 

Krieger, M, 2001. Scavenger receptor class B type I is a multiligand HDL receptor that influences diverse physiologic systems. J Clin Invest 108, 793-797. 

Build materials with the kind of actuating response found in physiological systems such as muscle. 

Since OPC block ChE selectively in every cholinergic structure (bland N-cholinoreceptive systems), practically all physiological systems and organs can be involved in a pathological process. At that, changes in activity of the central and peripheral nervous systems as well as the resulting impairments in respiratory and cardiac activities have a critical influence on an outcome of the poisoning. 

Over the last decade, there has been a steady increase in the popularity and usage of natural products to enhance overall health. These nutraceuticals and functional foods modulate the function of various physiological systems including the immune system. By altering immunity, it is possible to augment an individual s ability to ward off infection, or suppress autoimmunity and chronic inflammatory diseases. Thus, the renaissance of herbal extracts as well as the increased consumption of other dietary components has afforded the public a relatively inexpensive way to self-medicate. 

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