Lecture 1 Notes

Lecture 1 Notes - Lecture 1 Robustness Stability and Homeostasis(Slide 1(Slide 2 Bodies can be thought of as very complex machines and this

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Lecture 1 Robustness, Stability and Homeostasis (Slide 1.) (Slide 2.) Bodies can be thought of as very complex machines and this complexity can lead to instability. Parts can break down or not function properly, there are millions of interacting components and problems can potentially arise in a myriad of different ways. Yet for most of us the system works very well and there are generally few problems until we begin to enter old age. This doesn't come about by chance, mechanisms have evolved to maintain stability in all living organisms. These mechanisms are generally described by analogy to engineering concepts. There are two basic ideas: 1. Control theory, feedback loops, homeostasis 2. Robust networks Homeostasis History (Slide 3.) The idea that the body must achieve and maintain a balance is a very old one. Many ancient eastern religions revolve around the concept of achieving balance in the body and mind. Buddhism is one of the earliest examples and ancient yogic texts provide explicit instructions for achieving this ideal. The concept is also central to traditional Chinese medicine, which focuses on balancing yin and yang, a concept that is derived from Taoism. (Slide 4.) This very ancient concept of maintaining balance within the body is not all that far removed from the modern textbook concept of homeostasis. This figure, from a recent physiology textbook, wouldn't look out of place in an ancient Sanskrit text. Now the goal is to maintain homeostasis, which essentially means balance in this context. (Slide 5.) The first generally recognized description of the concept of homeostasis in western medicine was by Claude Bernard in 1856 - "The constancy of the internal environment is the condition for a free and independent life“. In other words, the ability of animals to survive in often stressful and varying environments reflects their ability to maintain a stable internal environment. The function of the body's cells and cellular physiology and biochemistry is dependent upon the maintenance of a stable internal state. (Slide 6.) The term homeostasis was first coined by Walter Cannon in 1932. The term is derived from two Greek words, homeo – similar and stasis – condition. The emphasis on similar (homeo) versus same (homo) is deliberate. The physiological system is not viewed as static, but instead as somewhat flexible in its ability to respond to changing environmental conditions. (Slide 7.) Cannon described some basic principles of homeostasis.
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2 It is hard to overemphasize the complexity of the mammalian body. With complexity comes the possibility of catastrophic breakdown. During the course of evolution homeostatic mechanisms were acquired in order to maintain stability over the complete range of environmental conditions that an animal was likely to encounter. If this wasn't the case the animal would go extinct.
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This note was uploaded on 02/15/2011 for the course BIO 328 taught by Professor Cabot during the Fall '07 term at SUNY Stony Brook.

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Lecture 1 Notes - Lecture 1 Robustness Stability and Homeostasis(Slide 1(Slide 2 Bodies can be thought of as very complex machines and this

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