Equilibrium Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Equilibrium and links to relevant pages within the course.
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| An Introduction to the Fundamentals of Coagulation The ability of the body to maintain a state of homeostasis, or physiological equilibrium, is absolutely essential for effective, efficient functionality of all body systems.
The mechanisms involved in blood coagulation, also known as hemostasis or blood clotting, serve to illustrate this concept.
Hemostasis is the cessation of free blood flow, external to the vascular system, when a vessel wall has been breached.
With the maintenance of homeostasis in mind, it is vital that the body be able to rapidly repair vascular damage, arresting blood flow in the process, while simultaneously maintaining blood in a fluid state within the vascular compartment.
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| Coagulation Disorders This course began with a discussion on homeostasis, the body’s desire to maintain a status of physiological equilibrium. Our inborn system of chemical checks and balances, activators and inhibitors, can be disrupted by numerous factors, two of the more common being acquired disease states and disorders passed on to offspring via inheritance. In regard to coagulation, both disease status and genetics can adversely affect the functionality of many hemostatic processes. Impaired hemostatic mechanisms, be it acquired in cases of disease or inherent, may result in situations of either hemorrhage or thrombosis. A situation of hemorrhage, or bleeding external to the vasculature, most often stems from physical vessel trauma, but may also arise from a wide variety of disease states. Thrombosis does not require physical trauma, and is the activation of hemostatic processes at an inappropriate time in an inappropriate place, and may arise from a number of inherited or acquired disease states. The following pages are intended to serve as an introduction to some of the more commonly encountered coagulation disorders. | View Page |
| Regulation of Iron Equilibrium Regulation of iron equilibrium occurs mainly through the process of absorption. Iron is absorbed through the mucosal cells lining the duodenum. A variety of proteins are involved in this process. Hepcidin, an antimicrobial protein primarily produced in the liver, has been recently found to be a major (negative) regulator of dietary iron absorption by disrupting cellular iron transport in the intestine. Decreased levels of hepcidin are related to increased iron absorption into the bloodstream. Hepcidin is increased in response to iron overload and inflammation. (4)Additional proteins involved in iron metabolism include transferrin (Tf), transferrin receptor (TfR), ferroportin, HFE protein, hemojuvelin, and others. Their roles in iron absorption are complex and in some instances incompletely understood.Factors affecting iron absorption include: Tissue stores, e.g., decreased stored iron is associated with a decrease in hepcidin and increase in iron absorption. Rate of hematopoietic activity, e.g., an increased rate of erythropoiesis is associated with a decrease in hepcidin and an increase in iron absorption. Oxygen concentration in tissues, e.g., hypoxia decreases hepcidin and increases iron absorption, thereby promoting increased erythopoiesis. Dietary intake, including form of iron ingested, e.g., heme iron is more readily absorbed than non-heme forms of iron. Condition of GI tract mucosal cells Intraluminal factors, e.g. intestinal motility | View Page |
| Protein Binding Most drugs are bound to proteins when they circulate in the body. Albumin is a major drug-binding protein in serum. Albumin is an alkaline protein, so acidic and neutral drugs primarily bind to it. If albumin binding sites become saturated, acidic and neutral drugs can bind to lipoproteins. Alkaline drugs tend to bind to globulins, particularly to the globulin, alpha-1 acid glycoprotein. Only free, unbound drugs are able to bind drug receptors and have therapeutic effects. An equilibrium exists in the systemic circulation between a free and protein-bound drug and between a free and receptor-bound drug. This is illustrated in the image to the right. | View Page |
| Protein Availability and Drug Dosing Drug-binding proteins in serum can fluctuate in disease states. For example, if albumin levels fall, as can occur in liver failure or nephrotic syndrome, less albumin will be available for drug binding; a subsequent dose may produce a toxic concentration of free drug.The image on the right illustrates the loss of equilibrium between a protein-bound drug and a free drug when drug-binding proteins are diminished.Doses of drugs that are highly protein-bound may need to be adjusted in patients with lower drug-binding protein levels. Examples of some common drugs that are highly protein-bound include thyroxine, warfarin, diazepam, heparin, imipramine and phenytoin. � | View Page |