Homeostasis

12 Key excerpts on "Homeostasis"

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  eBook - PDF

  Case Studies in Physiology and Nutrition

  • Lynne Berdanier, Carolyn D. Berdanier(Authors)
  • 2009(Publication Date)
  • CRC Press

    (Publisher)

  21 3 chapter Homeostasis What Is Homeostasis? Homeostasis (homeo = same, stasis = stay) is a term used to describe the condition of bal-ance of the internal environment in the body where a variety of regulatory processes work to maintain constancy of these internal systems within operational limits. The regulation of body temperature and pH are two examples of homeostatic regulation. Other examples include the body’s relatively stable blood glucose and electrolyte concentrations and acid-base balance. Much of this regulation occurs via a system of communication orchestrated by the endocrine system. This system releases hormones in response to both external and internal signals. The hormones in turn travel in the blood from their point of origin to their target tissues, which in turn respond to this shift in the environment. This can be visualized as a cascade: A change in the environment leads to a hormone response that in turn leads to a metabolic response. In many cases the brain is the master orchestrator of this response. As discussed in Chapter 2, when Homeostasis is perturbed and not re- established, disease can result. Sometimes when Homeostasis is perturbed, the body adjusts to this perturbation and a new homeostatic regulatory state is achieved. This is called adap-tation . An example of this is when an individual leaves a warm environment and enters a cold environment. Perhaps the individual lives in Florida and has taken a trip to Vermont in February. This individual has managed to thrive in Florida’s warm and humid environ-ment. Now, having flown to Vermont where it is drier and much colder, with ice and snow, this individual will need to adjust to this change in environmental conditions. At first with a light coat on, the individual feels cold. Shivering occurs and the individual gener-ates additional body heat via brown fat thermogenesis. The individual also modifies his/ her behavior: puts on a warm coat, hat, gloves, and boots.

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  Fundamentals of Applied Pathophysiology, 1st Asia-Pacific Edition, P-eBK

  • Ian Peate, Sufyan Akram, Michele Dowlman, Ellie Kirov, Bonnie Williams(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  The word Homeostasis is derived from the Greek words for ‘similar’ and ‘standing still’; it refers to any process that living organisms employ to actively maintain stable internal conditions that are necessary for survival. In 1930, the term was used by Walter Cannon, a doctor. In his text, The wisdom of the body, he describes how the body maintains constant levels of temperature and other vital conditions; for example, the water, salt, sugar, protein, fat, calcium and oxygen contents of the blood. In health, the body does all the work that is required to maintain itself through a wide range of living processes, including the excretion of waste products and the inhalation of oxygen so as to release energy from sugar. It also uses the process of Homeostasis to maintain itself in balance; it makes just the right number of cells to replace those cells that have worn out, and it produces just the right amounts of hormones to signal a reaction that is needed to maintain function. Maintaining Homeostasis requires the body to continuously monitor its internal conditions. From body temperature to blood pressure to the levels of certain nutrients, each physiological condition has a particular set point. When disruption of Homeostasis is mild and temporary, the cells of the body can quickly restore balance in the internal environment. However, if disruption is sustained and extreme, then Homeostasis fails, leading to illness and eventual death (Tortora et al., 2022). Nurses often care for people whose ability to maintain Homeostasis is impaired. When this occurs, it becomes essential that the nurse can detect subtle changes indicating altered Homeostasis, initiate the most appropriate response, escalate concerns to other healthcare staff and commence care that is evidence‐based. It is also important to be able to clearly communicate the changes to the patient, their family or carers, and be able to explain any treatments that are provided or that are being considered.

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  Thermodynamic Bases of Biological Processes

  Physiological Reactions and Adaptations

  • A. I. Zotin(Author)
  • 2013(Publication Date)
  • De Gruyter

    (Publisher)

  98 2. The Stable State of Organisms 2.2 Homeostasis and homeorhesis The problem of biological system stability is closely linked to the notion of Homeostasis. This term was introduced into biology rather a long time ago (Cannon, 1929, 1932) and now has become wide spread (Rosen, 1967; Ivanov, 1972; Mal-enkov, 1976; Novoseltsev, 1978; Gorizontov, 1981; Shidlovsky, 1982; Hardy, 1983; Grodzinsky, 1987). Despite this fact, the notion of Homeostasis has not yet been clearly defined. Usually Homeostasis describes the property of living systems to maintain their internal state during occasional fluctuations in environmental factors. If we accept this definition Homeostasis includes the idea of the steady state in living systems, as well as the process of maintaining this steady state. The original sense attached to this term by Cannon (1929) was analogous to the notion of equilibrium, i.e. he used this term to designate only the steady state of living systems. Further on the idea of Homeostasis came to designate not only the regulated state, but also the regulatory mechanisms, maintaining the steady state (Hardy, 1983). In our view the regulated state, i.e. the steady state of a living system, and process regulation in this state are not to be united through one term (Zotin, Zotina, 1987). From the thermodynamic point of view the notion of a steady state in an organized systems is rather well defined and there is no need to introduce a special term to designate such a state. The steady state of a thermodynamic system is linked to the principle of minimum energy dissipation and corresponds to that state of the system which has the minimum rate of entropy production (1.117). Thus, it is appropriate to refer the term Homeostasis to regulation mechanisms maintaining the steady state. Proceeding from this we have defined this term as follows: Homeostasis is the process of maintaining the steady state of an organized system (Zotin, Zotina, 1987).

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  Behavioral Neuroscience

  • George Spilich(Author)
  • 2023(Publication Date)
  • Wiley

    (Publisher)

  Every living organism must meet certain requirements to survive, and humans are no exception. We must maintain a body temperature within a certain range, neither too hot nor too cold. We need enough fluids so that our blood can carry glucose, oxygen, and other nutrients throughout our body. We need enough fuel in the form of glucose to power our cells. Wherever we go and whatever we do, our nervous system is working constantly behind the scenes to ensure that our essential biological systems can function despite changing conditions around us. Balance and Change in the Body MCAT In 1926, physiologist Walter Cannon coined the term Homeostasis to describe physiological processes that only function within a specific range of values. The word Homeostasis comes from the Greek for same (homeo) and standing still (stasis), and Homeostasis is defined as a regulated internal state that supports life. In prior chapters you have already seen how 176 C H A P T E R 7 Homeostatic Regulation of the Internal Environment imbalances in certain ions or neurotransmitters can have serious effects on our health and can even be fatal. Other factors that must stay in balance include blood pressure, oxygen levels, temperature, and pH. Intuitively, you can see that humans must remain within a certain range in all of these parameters to survive and thrive (Figure 7.1). The point at which systems tend to stabilize is called the set point. If your blood pressure significantly exceeds the set point, you may have a stroke, but if it falls too far below this same set point, you will pass out. Too far in either extreme is fatal. Cannon’s perspective that our nervous system defends set points through homeostatic processes has been a valuable tool for understanding the biological basis of behavior, but in 1988, neuroscientist Peter Sterling and his colleague Joseph Eyer proposed a modification of Homeostasis they termed allostasis.

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  The Physiological Basis of Behaviour

  Neural and Hormonal Processes

  • Kevin Silber(Author)
  • 2005(Publication Date)
  • Routledge

    (Publisher)

  6 Homeostasis

  Introduction

  In this chapter we consider Homeostasis as an example of how the CNS, ANS and endocrine system work together. The term Homeostasis refers to the maintenance of a relatively stable state within our bodies. In the first part of the chapter we take a closer look at exactly what this means. The rest of the chapter details three major homeostatic mechanisms, namely, the regulation of our nutritional content (eating), the regulation of our water content (drinking), and the regulation of our body heat (temperature regulation). As you work through the chapter you will see that all three mechanisms are kept in balance by a combination of hormonal and ANS activity, all of which is coordinated by central brain processes.

  What is Homeostasis?

  As I am writing this book in World Cup year I will start, if I may, with a football analogy. Imagine that you want to have a game of football. If the ball is not pumped up enough then it will not bounce properly. If it is blown up too much then it will burst. Indeed, professional footballers will tell you that small diversions from the correct pressure make it difficult to play properly. There is, therefore, a limited range of pressures over which the football can function as a football. The same is true of the constituents of our bodies. For example, many of the chemical reactions in our body are helped by the presence of enzymes. Enzymes will only work within a limited temperature range. Therefore, the body must maintain its temperature within certain limits. The mechanisms for this and all of the other balances are called homeostatic mechanisms.

  There are a number of features of Homeostasis that are worth pointing out before we look at the details.

  • The ideal range for any component is called the set point

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  Fundamentals of Applied Pathophysiology

  An Essential Guide for Nursing and Healthcare Students

  • Ian Peate(Author)
  • 2021(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  This chapter introduces the reader to the concept of Homeostasis. Homeostasis is the key to life, and vital signs, for example, are a measure of Homeostasis. Being healthy for many people means being independent of clinical intervention and to be able to undertake the activities of living. In order to do this, the body needs to engage with Homeostasis. Understanding the theoretical underpinning of Homeostasis for health is essential for safe and effective care, for accurate clinical decision‐making and for restoration of patients to health.

  The word Homeostasis is derived from the Greek words for ‘similar’ and ‘standing still’; the term refers to any process that living things employ to actively maintain stable conditions that are necessary for survival. In 1930 the term was used by Walter Cannon, a doctor. In his text, The Wisdom of the Body, he describes how the body maintains constant levels of temperature and other vital conditions, for example, the water, salt, sugar, protein, fat, calcium and oxygen contents of the blood.

  In health, the body does all the work that is required to maintain itself by a wide range of living processes, including the excretion of waste products and the inhalation of oxygen so as to release energy from sugar. It also uses the process of Homeostasis to maintain itself in balance, it makes just the right number of cells to replace those cells that have worn out and it produces just the right amount of hormones to signal a reaction that is needed to make things happen. Maintaining Homeostasis requires the body to continuously monitor its internal conditions. From body temperature to blood pressure to the levels of certain nutrients, each physiological condition has a particular set point. When disruption of Homeostasis is mild and temporary, the cells of the body can quickly restore balance in the internal environment. However, if disruption is sustained and extreme, then Homeostasis may fail (Tortora and Derrickson 2017

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  Concepts in Biology

  A Historical Perspective

  • Marc Gilbert, Sergej Pirkmajer(Authors)
  • 2023(Publication Date)
  • Wiley-ISTE

    (Publisher)

  4 Integrative Aspects: From Cellular to Whole-Body Level 4.1. Homeostasis equilibrium: dynamic steady state Homeostasis is a core concept necessary for understanding the many regulatory mechanisms in physiology. C. Bernard originally proposed the concept of the constancy of the “milieu intérieur”, that would allow biological processes to proceed despite variations in the external environment (Bernard 1879). The concept was further explored by W. Cannon who introduced the term “Homeostasis” in describing how key physiological variables are maintained within a predefined range by feedback mechanisms (Cannon 1929). In the 1960s, homeostatic regulatory mechanisms in physiology began to be described and focused on active mechanisms which keep a regulated variable in the internal environment within a range of values compatible with life. We should keep in mind that passive mechanisms such as water movement between capillaries are also involved in maintaining Homeostasis, but these are not discussed here. There are additional concepts which are central to understand the function of a homeostatic mechanism. Firstly, it is important to distinguish two types of variables in homeostatic systems. Variables that are maintained at a stable level (near set point), by homeostatic circuit(s), such as blood glucose or core body temperature, are called “regulated variables”. In contrast, variables that are manipulated in order to maintain the regulated variables within desired ranges are called “controlled variables”, such as glycogenolysis, glycogenesis, glycolysis, gluconeogenesis and glucose transport from the blood into tissues. Multiple controlled variables typically contribute to the stability of a given regulated variable (Kotas and Medzhitov 2015). Thus, regulated variables refer to quantities, whereas controlled variables refer to processes. The concept of set point For a color version of all the figures in this chapter, see www.iste.co.uk/gilbert/concepts.zip.

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  Human Physiology

  • Bryan H. Derrickson(Author)
  • 2019(Publication Date)
  • Wiley

    (Publisher)

  The maintenance of relatively stable conditions in the body’s internal environment is known as Homeostasis (ho - ′me - -o - -STA - -sis; homeo- = sameness; -stasis = standing still). It occurs because of the ceaseless interplay of the body’s many regulatory processes. Homeostasis is a dynamic steady state. The term dynamic is used to refer to Homeostasis because each regulated parameter can change over a narrow range that is compatible with life. For example, the level of glucose is maintained between 70 and 110 milli- grams of glucose per 100 milliliters of blood. It normally does not fall too low between meals or rise too high even after eating a high-glucose meal. The term steady state is used to refer to Homeostasis because energy is needed to keep the regulated parameter at a relatively constant level. Steady state is not the same as equilibrium. In an equilibrium, conditions remain con- stant without the expenditure of energy. Each structure in the body, from the cellular level to the systemic level, contributes in some way to keeping the internal environment of the body within normal limits. Maintenance of Body Fluid Volume and Composition Is Essential to Homeostasis An important aspect of Homeostasis is maintaining the volume and composition of body fluids, dilute, watery solutions Blood capillary Body cells Intracellular fluid Extracellular fluid: Interstitial fluid Plasma Question What is the difference between interstitial fluid and plasma? The fluid within cells is intracellular fluid; the fluid outside cells is extracellular fluid, which consists of interstitial fluid and plasma. FIGURE 1.3 Body fluid compartments. 8 CHAPTER 1 An Introduction to Physiology for energy. During this process, the cells produce waste products, which enter interstitial fluid and then move across blood capil- lary walls into plasma. The cardiovascular system transports these wastes to the appropriate organs for elimination from the body into the external environment.

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  Physiology and Anatomy for Nurses and Healthcare Practitioners

  A Homeostatic Approach, Third Edition

  • John Clancy, Andrew McVicar(Authors)
  • 2017(Publication Date)
  • Taylor & Francis

    (Publisher)

  4 The concept of Homeostasis helps to explain the importance to health of maintaining an optimal environment within which cells must func-tion. ‘Optimal’ does not necessarily equate with constancy. It also relates to the control of change observed during daily activities of liv-ing, times of stress, illness and postoperative recovery, and during the developmental phases of the lifespan. 5 Homeostatic control relies mainly upon negative feedback mecha-nisms that act to reverse changes and regulate parameters close to the optimal value. 6 Prevention of parameter variation can be detrimental under some cir-cumstances. The promotion of change via positive feedback mecha-nisms or through a resetting of homeostatic setpoints is then of benefit. 7 Ill health arises when there is a failure to maintain homeostatic func-tions, either at tissue or organ levels of organization. The interdepend-ency of tissue functions means those homeostatic disturbances and associated signs and symptoms will also arise secondarily to the pri-mary disorder. 8 Healthcare practices are related to Homeostasis since they provide the extrinsic effectors that act to restore Homeostasis in patient. 9 Homeostasis provides an interactional framework that gives structure to nature–nurture considerations on the basis of well-being and healthcare practices. Chapter 2 CELL AND TISSUE FUNCTIONS Cellular level of organization 23 Cellular anatomy and physiology 25 Homeostatic mechanisms by which substances are 28 transported across the cell membrane Cell organelles 32 Genes and cell division 42 Tissues and tissue function 52 Organs 58 Organ systems 59 Summary 59 References 59 Further reading 60 The structure of the body can be described on four levels of organization: the chemical level (see Chapter 4), the cellular and tissue levels (both levels described in this chapter), and the organ system levels (see Chapters 7–18).

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  Ecological Stoichiometry

  The Biology of Elements from Molecules to the Biosphere

  • Robert W. Sterner, James J. Elser(Authors)
  • 2017(Publication Date)
  • Princeton University Press

    (Publisher)

  It has been said that Homeostasis is the essence of life. Organisms regulate many of their properties, including water balance, pH, and others. In ecological stoichiometry, Homeostasis is observable in the patterns of variation in nutrient elements in organisms relative to their external world, including the resources they eat. Kooijman (1995) defined Homeostasis in a stoichiometric context as follows: “The term Homeostasis is used to indi-cate the ability of most organisms to keep the chemical composition of their body constant, despite changes in the chemical composition of the environment, including their food.” An organism’s stoichiometry is the pat-tern that results from different degrees of Homeostasis operating on chem-ical composition. Homeostasis generates different degrees of variation in chemical substances in living things. Because in ecological stoichiometry, Homeostasis refers to changes in matter in living things, it is often used when discussing growth. However, as a general biological concept, homeo-stasis may occur with or without growth. We will see that differences in the strength of Homeostasis have numerous ecological consequences. Homeo-stasis is a major reason for this book’s existence. Without it, ecological stoichiometry would be a dull subject. Another easily understood case would be if a consumer’s nutrient con-tent were independent of the chemical composition of its food. In our now familiar plot of consumer versus resource stoichiometry, any horizontal line segment above, below, or intersecting with the 1:1 line would repre-sent this situation. We refer to these situations as “ strict Homeostasis ” STOICHIOMETRY AND Homeostasis 15 (Fig. 1.3B, solid lines). A related term that will come up frequently later is balanced growth . These two terms describe a stoichiometric equilib-rium where the proportions of substances in an organism do not change.

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  Fundamentals of Children's Anatomy and Physiology

  A Textbook for Nursing and Healthcare Students

  • Ian Peate, Elizabeth Gormley-Fleming(Authors)
  • 2014(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  Fundamentals of Children’s Anatomy and Physiology: A Textbook for Nursing and Healthcare Students, First Edition. Edited by Ian Peate and Elizabeth Gormley-Fleming. © 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd. Companion website: www.wileyfundamentalseries.com/childrensA&P Chapter 2 Homeostasis Mary Brady Faculty of Health, Social Care and Education, Kingston University, London, UK Aim The aim of this chapter is to help you to develop insight and understanding of homeostatic mechanisms within the bodies of children and young people (0–18 years of age). By gaining further understanding and developing your insight you will be able to provide high quality safe and effective informed care. On completion of this chapter the reader will be able to: • Describe Homeostasis and how it is regulated. • Describe what is meant by feedback mechanisms. • Describe the homeostatic mechanisms. • Describe how energy is produced. Learning outcomes • What is Homeostasis? • How does the body receive feedback to ensure equilibrium is maintained within the body? • What influence does the central nervous system have on Homeostasis? • What hormones are involved in Homeostasis? • How does the body maintain water balance? • How does the body maintain its balance of salts? • How does the body maintain its balance of oxygen and carbon dioxide? • What is the stimulus for breathing in the newborn? • What is the stimulus for breathing in the older child or young person? • What are differences between the essential and non-essential amino acids? Test your prior knowledge 18 Chapter 2 Homeostasis Introduction Within the body, several mechanisms exist to ensure that the internal environment remains within a narrow set of parameters, regardless of the external environment. This process is called Homeostasis and illness occurs when there is a disruption to this normal homeostatic control. It is often when Homeostasis is disrupted that holistic nursing care is required.

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  Reversibility of Chronic Degenerative Disease and Hypersensitivity, Volume 1

  Regulating Mechanisms of Chemical Sensitivity

  • William J. Rea, Kalpana Patel(Authors)
  • 2010(Publication Date)
  • CRC Press

    (Publisher)

  The blood pressure increase is such that only one third as much would occur if this control system were not present. The gains of some other physiological homeostatic control systems are much greater than that of the baroreceptor system. For instance, as the second example, the gain of the system controlling body temperature is about − 33°F net gain. Therefore, with the best gain plus chronic stimuli, the temperature will not return to normal, but will be much closer to normal than the blood pressure in the aforemen-tioned example. Therefore, one can see that the homeodynamics of temperature control mechanism is much more effective than the baroreceptor control mechanism. Thus, if in certain patients like the chemically sensitive who are usually cold, with temperatures ranging from 89 to 97°F, the homeostatic control mechanism is constantly being thrown off. The dynamics of Homeostasis will be difficult to obtain and maintain even under the best of circumstances in these chemically sensitive individuals because so much energy is spent to equalize or stabilize the dynamics of the homeostatic adjustment response. This characteristic may well explain one reason why the chemically sensitive are so fragile at maintaining equilibrium and are frequently disturbed by small doses of a pollutant. Their homeo-static gain is less than ideal and therefore, these patients are hypothermic. If the chronic stimulus con-tinues and the percent gain continues to be less than the normal homeostatic response, informational and then metabolic changes will occur, followed by tissue changes, and eventually end-organ failure. The positive feedback mechanism is the third characteristic of homeostatic control . The body uses positive feedback infrequently because positive feedback can be tied to vicious downward cycles.

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