The Internal Environment and Homeostasis

An amoeba and a human liver cell both obtain their energy by breaking down certain organic nutrients. The chemical reactions involved in this intracellular process are remarkably similar in the two types of cells and involve the utilization of oxygen and the production of carbon dioxide. The amoeba picks up oxygen directly from the fluid surrounding it (its external environment) and eliminates carbon dioxide into the same fluid. But how can the liver cell and all other internal parts of the body obtain oxygen and eliminate carbon dioxide when, unlike the amoeba, they are not in direct contact with the external environment—the air surrounding the body?

Figure 1-2 summarizes the exchanges of matter that occur in a person. Supplying oxygen is the function both of the respiratory system, which takes up oxygen from the external environment, and of the circulatory system, which distributes the oxygen to all parts of the body. In addition, the circulatory system carries the carbon dioxide generated by all the cells of the body to the lungs, which eliminate it to the exterior. Similarly, the digestive and circulatory systems working together make nutrients from the external environment available to all the body's cells. Wastes other than carbon dioxide are carried by the circulatory system from the cells that produced them to the kidneys and liver, which excrete them from the body. The kidneys also regulate the amounts of water and many essential minerals in the body. The nervous and hormonal systems coordinate and control the activities of all the other organ systems.

Thus the overall effect of the activities of organ systems is to create within the body an environment in

CHAPTER ONE A Framework for Human Physiology

Vander et al.: Human I. Basic Cell Functions

Physiology: The Mechanism of Body Function, Eighth Edition

CHAPTER ONE A Framework for Human Physiology

System

Major Organs or Tissues

Primary Functions

Circulatory

Heart, blood vessels, blood (Some classifications also include lymphatic vessels and lymph in this system.)

Transport of blood throughout the body's tissues

Respiratory

Nose, pharynx, larynx, trachea, bronchi, lungs

Exchange of carbon dioxide and oxygen; regulation of hydrogen-ion concentration

Digestive

Mouth, pharynx, esophagus, stomach, intestines, salivary glands, pancreas, liver, gallbladder

Digestion and absorption of organic nutrients, salts, and water

Urinary

Kidneys, ureters, bladder, urethra

Regulation of plasma composition through controlled excretion of salts, water, and organic wastes

Musculoskeletal

Cartilage, bone, ligaments, tendons, joints, skeletal muscle

Support, protection, and movement of the body; production of blood cells

Immune

White blood cells, lymph vessels and nodes, spleen, thymus, and other lymphoid tissues

Defense against foreign invaders; return of extracellular fluid to blood; formation of white blood cells

Nervous

Brain, spinal cord, peripheral nerves and ganglia, special sense organs

Regulation and coordination of many activities in the body; detection of changes in the internal and external environments; states of consciousness; learning; cognition

Endocrine

All glands secreting hormones: Pancreas, testes, ovaries, hypothalamus, kidneys, pituitary, thyroid, parathyroid, adrenal, intestinal, thymus, heart, and pineal, and endocrine cells in other locations

Regulation and coordination of many activities in the body

Reproductive

Male: Testes, penis, and associated ducts and glands

Female: Ovaries, uterine tubes, uterus, vagina, mammary glands

Production of sperm; transfer of sperm to female

Production of eggs; provision of a nutritive environment for the developing embryo and fetus; nutrition of the infant

Integumentary

Skin

Protection against injury and dehydration; defense against foreign invaders; regulation of temperature

which all cells can survive and function. This fluid environment surrounding each cell is called the internal environment. The internal environment is not merely a theoretical physiological concept. It can be identified quite specifically in anatomical terms. The body's internal environment is the extracellular fluid (literally, fluid outside the cells), which bathes each cell.

In other words, the environment in which each cell lives is not the external environment surrounding the entire body but the local extracellular fluid surrounding that cell. It is from this fluid that the cells receive oxygen and nutrients and into which they excrete wastes. A multicellular organism can survive only as long as it is able to maintain the composition of its internal environment in a state compatible with the sur vival of its individual cells. In 1857, Claude Bernard clearly described the central importance of the extracellular fluid: "It is the fixity of the internal environment that is the condition of free and independent life. . . . All the vital mechanisms, however varied they may be, have only one object, that of preserving constant the conditions of life in the internal environment."

The relative constancy of the internal environment is known as homeostasis. Changes do occur, but the magnitudes of these changes are small and are kept within narrow limits. As emphasized by the twentieth-century American physiologist, Walter B. Cannon, such stability can be achieved only through the operation of carefully coordinated physiological processes. The activities of the cells, tissues, and organs must be

Vander et al.: Human I I. Basic Cell Functions I 1. A Framework for Human I I © The McGraw-Hill

Physiology: The Physiology Companies, 2001

Mechanism of Body Function, Eighth Edition

A Framework for Human Physiology CHAPTER ONE

Nutrients

Salts

Water out

O2 in

Nutrients

Salts

Water

Extracellular Fluid Plasma

Unabsorbed matter

Organic waste

Salts

Water

External environment

FIGURE 1-2

Exchanges of matter occur between the external environment and the circulatory system via the digestive, respiratory, and urinary systems. Extracellular fluid (plasma and interstitial fluid) is the internal environment of the body. The external environment is the air surrounding the body.

Unabsorbed matter

Organic waste

Salts

Water

External environment

FIGURE 1-2

Exchanges of matter occur between the external environment and the circulatory system via the digestive, respiratory, and urinary systems. Extracellular fluid (plasma and interstitial fluid) is the internal environment of the body. The external environment is the air surrounding the body.

regulated and integrated with each other in such a way that any change in the extracellular fluid initiates a reaction to minimize the change.

A collection of body components that functions to keep a physical or chemical property of the internal environment relatively constant is termed a homeo-static control system. As will be described in detail in Chapter 7, such a system must detect changes in the magnitude of the property, relay this information to an appropriate site for integration with other incoming information, and elicit a "command" to particular cells to alter their rates of function in such a way as to restore the property toward its original value.

The description at the beginning of this chapter of how sweating is brought about in response to increased heat generation during exercise is an example of a homeostatic control system in operation; the sweating (more precisely, the evaporation of the sweat) removes heat from the body and keeps the body temperature relatively constant even though more heat is being produced by the exercising muscles.

Here is another example: A mountaineer who ascends to high altitude suffers a decrease in the concentration of oxygen in his or her blood because of the decrease in the amount of oxygen in inspired air; the nervous system detects this change in the blood and increases its signals to the skeletal muscles responsible for breathing. The result is that the mountaineer breathes more rapidly and deeply, and the increase in the amount of air inspired helps keep the blood oxy gen concentration from falling as much as it otherwise would.

We emphasized at the beginning of this chapter the intimate relationship between physiology and medicine. Another way of putting it is that physicians, for the most part, diagnose and treat disease-induced disruptions of homeostasis.

To summarize, the activities of every individual cell in the body fall into two categories: (1) Each cell performs for itself all those fundamental basic cellular processes—movement of materials across its membrane, extraction of energy, protein synthesis, and so on—that represent the minimal requirements for maintaining its own individual integrity and life; and (2) each cell simultaneously performs one or more specialized activities that, in concert with the activities performed by the other cells of its tissue or organ system, contribute to the survival of the body by maintaining the stable internal environment required by all cells.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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Responses

  • Dahlak
    Why is interstitial fluid called the internal environment of the body?
    7 years ago
  • robert
    What organ systems are associated with exchanges in the external and internal environment ?
    7 years ago
  • Manuela
    What keeps the body internal environment from the external environment?
    7 years ago
  • bruno graham
    What is interstitial fluid why it is called internal inviornment of body?
    7 years ago
  • samuel
    Is plasma intracellular or extracellular?
    7 years ago
  • habte
    What is internal environment cell?
    7 years ago
  • sagramor
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    7 years ago
  • michael
    Why is extracellular fluid referred to as the bodys internal environment?
    7 years ago
  • Raino Tervo
    Does intracellular fluid receive oxygen and nutrients?
    7 years ago
  • almaz
    What is the function of internal environment in the bodies?
    7 years ago
  • Regina
    What is the name of the internal environment (fluid) within the cells?
    7 years ago
  • alexandra
    Why is interstitial fluid called the internal envirvoment of the body?
    7 years ago
  • Brenda Anderson
    What is the name of the internal environment fluid of the body that baths the bodies cells in fluid?
    7 years ago
  • Bildat
    What is the name of internal environment of the body that bathes the bodies.cells in fluid?
    7 years ago
  • manlio dellucci
    Is the intracellular fluid part of the internal environment?
    7 years ago
  • amaranto
    Is extracellular fluid internal or external?
    7 years ago
  • eija-riitt
    How does the digestive and circulatory systems maintain a constant internal environment?
    6 years ago
  • jole
    What is one aspect of internal environment homeostasis?
    6 years ago
  • Baldo
    How amoeba homeostasis change in environmental temperature?
    6 years ago
  • Genet Mebrahtu
    What is the relationship between the internal and external environments of the digestive system?
    6 years ago
  • keir
    Why is inetstitial fluid also called internal environment?
    6 years ago
  • tess
    How does oxygen enter the body's internal environment?
    6 years ago
  • betty
    What mediates internal and external responses to the body's surroundings?
    6 years ago
  • sabine
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    6 years ago
  • riley
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    6 years ago
  • gabriella
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    5 years ago
  • adelard
    What organ system are associated with exchanges between the internal and external environment?
    5 years ago
  • severi
    What is the difference between the external and internal enviroments of the human body?
    5 years ago
  • ROBERT
    What organs are associated with the external environment?
    5 years ago
  • edda longo
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    5 years ago
  • Jackson
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    5 years ago
  • taziano
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    5 years ago
  • lorenzo
    How the internal activities coordinates in the body physiolgy?
    4 years ago
  • negisti
    Which organ system does not have direct contact with the external enviornment?
    4 years ago
  • stefan
    How the body co ordinates its internal activities?
    4 years ago
  • tom
    How the bosy coordinates its internal activities?
    4 years ago
  • bisrat
    How nutrients,oxygen and wastes are exchange the fetus and the matter?
    4 years ago
  • rogelio messer
    What 2 systems maintain homeostasis for bodies internal enviro?
    4 years ago
  • marina
    How the body can coordinate with internal activity?
    4 years ago
  • caiden
    When excersing how does the body coordinate its internal activities?
    4 years ago
  • Kane
    How is information about the internal environment conveyed to the organ systems?
    4 years ago
  • toni ukkonen
    Which organ systems directly have contact between internal and external environment?
    4 years ago
  • iva
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    4 years ago
  • madihah
    How are nutrients exchanged between the body's external and internal environments?
    4 years ago
  • mathias
    How does the heart maintain homestasis of the body's internal environment?
    3 years ago
  • senay
    What is internal environemnt and external environemnt in homeostasis?
    3 years ago
  • brunilde
    Why is homeostasis,extracellular fluid called the internal environment of the body?
    3 years ago
  • ari-pekka
    How does an amoeba maintain its internal enviroment?
    3 years ago
  • marcel
    How does internal environment of a human body relate with homeostasis?
    3 years ago
  • THOMAS
    What are functions of the internal environment of homeostasis?
    3 years ago
  • eugene
    How do amoeba maintain a stable internal environment?
    3 years ago
  • Kelsie
    How does the body co ordinate its internal activities?
    3 years ago
  • germana
    Is interstitial fluid an external environment?
    3 years ago
  • alexis
    How does digestive system maintain its internal environment?
    3 years ago
  • Faye
    How the body coordinates when strenous activities?
    2 years ago
  • Wilma
    Why is the Interstitial fluid the internal enviroment of cell in homestasis?
    2 years ago
  • Seppo
    What makes the interstitial fluid the internal environment?
    2 years ago
  • arabella
    How does an amoeba maintain homeostasis?
    2 years ago
  • norbert
    Why is the interstitial fluid of extracellular fluid the internal environment in homeostasis?
    2 years ago
  • tricia
    What are the components of the internal environment of the body?
    2 years ago
  • Carla
    What is the difference between the external and internal environments of the body?
    2 years ago
  • aila black
    How is concentration of oxygen and carbon dioxide mantained constant in internal environment?
    2 years ago
  • Chilimanzar
    What is internal environment in physiology?
    2 years ago
  • pandora took-brandybuck
    When discussing homeostasis what is the internal environment?
    2 years ago
  • ivana
    Why is interstitial fluid called internal environmebt of the body?
    2 years ago
  • anna-liisa
    What make up the body internal enviroment?
    2 years ago
  • ruta
    What is the physiological importance of the internal environment?
    2 years ago
  • kati
    How are nutrients,oxygen and waste exchanged between the body's internal and external environments?
    2 years ago
  • Hamilcar
    What regulation of internal environment (liver and kidney)?
    2 years ago
  • arduino
    What is external environment in anatomy and physiology?
    2 years ago
  • sabine
    Is the internal environment made up of lymph?
    2 years ago
  • Helj
    What makes up the human body internal environment?
    2 years ago
  • phillipp richter
    Which body fluid forms the internal environment?
    2 years ago
  • Elina
    How the liver and kidney regulate the internal environment?
    2 years ago
  • Klaudia Baumgaertner
    What is homeostasis and is its external and internal environment?
    2 years ago
  • Fosco
    Which organ in body comnunicates with body cells and external enviroment?
    2 years ago
  • tegan
    What is an internal environment in anatomy?
    2 years ago
  • SUSANNA
    Why blood is called internal environment of body?
    2 years ago
  • brayden
    What are the five organs of the internal environment (homeostasis)?
    2 years ago
  • louie
    Where are the organs of the internal environment located?
    2 years ago
  • Cheri
    What is internal environment of homeostatis?
    2 years ago
  • roddy
    How does the function of the liver are connect with the regulation of the internal environment?
    2 years ago
  • Melanie
    Is the digestive system part of the body's external environment?
    2 years ago
  • Alastair
    Is internal enviroent similar homeostasis?
    2 years ago
  • Jan
    How does tissue fluid maintain homeostasis?
    2 years ago
  • andrew
    Which one cell are not contact with external environment?
    2 years ago
  • ALEXANDER
    What is the main organs that regulate the internal environment?
    2 years ago
  • gringamor
    Where can you locate human internal environment?
    2 years ago
  • ermias
    Why extra cellular fluid is called internal environment?
    2 years ago
  • BOWMAN
    Which organs are part of the internal environment?
    2 years ago
  • charlotte
    Why tissue fluid is called the internal environment of the body?
    2 years ago
  • lucie
    What are the parts of an internal environment of the human body?
    2 years ago
  • robert winkel
    How the blood forms internal environment of cell?
    2 years ago
  • Adelbert
    How does the internal and external transportation function in a human body?
    2 years ago
  • Brenton
    How the organs and circulatory keeps internal environment of our body?
    2 years ago
  • nina
    Why efc is called internel invironment of the body?
    2 years ago
  • Irene
    Why is the ISF of the ECF regarded as the internal environment of the body?
    2 years ago
  • donatella mazzi
    Why the extra cellular fluid is called the internal environment of the body definition in Guyton?
    2 years ago
  • Tarja
    What is the body's internal environment in which the fluid surrounds cells?
    2 years ago
  • robert
    What are the internal environment of cells and tissue intercellular?
    1 year ago
  • suoma huovi
    How do we regulate the internal enviroment?
    1 year ago
  • raniero
    Why Is Interstitial Fluid Regarded As The Internal Environment?
    1 year ago
  • panu
    How digestive system participate in maintaining the internal environment in constant conditions?
    1 year ago
  • semhar
    How body maintains its internal environment?
    1 year ago
  • Alyx
    Is interstial fluid a part of the external environment?
    1 year ago
  • David
    What is internal inviroment of the body.?
    1 year ago
  • Arcangela
    What is meant by the body internal environment?
    1 year ago
  • karys
    Does internal environment refer to as plasma?
    1 year ago
  • Ricardo Liggins
    Which system control internal environment of body?
    1 year ago
  • Bandobras
    What are relationship between hand and internal environment of the body?
    1 year ago
  • natsnet nebay
    What is the internal environment of humans?
    1 year ago
  • kelsey king
    What regulates the internal enviroment of amoeba?
    1 year ago
  • robel
    How digestive system mantain external environmental of the body?
    1 year ago
  • Amira
    WHAT IS REGULATION OF INTERNAL ENVORONMENT?
    1 year ago
  • OLIMPIA
    What make internal enviroment of homeostasis different from external?
    1 year ago
  • lucia
    What is the homeostasis of the internal environment important for survival of an individual?
    1 year ago
  • Lucia Douglas
    What is the constant internal environment of the body?
    1 year ago
  • mira
    What is the internal environmentof the hody?
    1 year ago
  • kyla craig
    Why ECF is termed as internal enviroment?
    1 year ago
  • kayley
    What does the digestive system exchange with the environment?
    1 year ago
  • Valente
    How does water maintain homeostasis?
    1 year ago
  • sara mueller
    How does amoeba maitam its interanal balance?
    1 year ago
  • daniella
    Why Homeostatic Control Of Composition Of Tissue Fluid Is Vital For Body Functions.?
    1 year ago
  • Gimja
    How amoeba involves in homeostasis?
    1 year ago
  • maria
    How pancreas bring about regulation of internal environment?
    12 months ago
  • Marina
    What does the internal environment of tje body consist of?
    12 months ago
  • SEMIRA
    What does the internal environment of the body refer to?
    12 months ago
  • joyce axford
    How does amoeba maitain its internal environment?
    12 months ago
  • Rita Samuel
    What is homeostasis in regulation of the internal environment?
    12 months ago
  • Monika Frankfurter
    What is the name of ahomone responsible for homeostasis process in emoeba?
    12 months ago
  • lavinia
    How does oxygen affect internal environment?
    11 months ago
  • gerardino palermo
    Why is ECF refered to as the external environment?
    11 months ago
  • marina
    What does our internal environment cosist of *homeostssi(?
    11 months ago
  • Isaia Schiavone
    How homeostasis of a cell is kept when their external environment changes?
    11 months ago
  • Katie-leigh
    How do plants maintain its internal environment?
    11 months ago
  • ulrich
    What is regulation of internal enviroment.?
    10 months ago
  • toini
    How do celks regulate internal environment?
    10 months ago
  • aziz welde
    WHAT IS REGULATION OF INTRRNAL EVIRONMENT?
    10 months ago
  • yvonne
    Which body fluid is considered to be the body's internal environment?
    10 months ago
  • azzeza
    What are the control systems among the intracellular and extracellular internal environment.?
    10 months ago
  • selassie ali
    How PFM disturbs the internal envirnment in physiology?
    9 months ago
  • tuija
    How does the body coordinate to monitor its internal activities?
    9 months ago
  • deborah
    Where would point out internal environment of body?
    8 months ago
  • yolanda burrowes
    How homeostasis is related to environmental physiology?
    8 months ago
  • manuela
    What are internal body mechanism?
    8 months ago
  • SWEN
    How do the human body systems respond to changfes in the external enviroment?
    8 months ago
  • veli
    What is external environment of the body in anatomy?
    7 months ago
  • stefanie
    Why is the extracellular fluid called the internal enviroment of the body?
    7 months ago
  • jennie graham
    How to maintain a stable internal environment in body?
    7 months ago
  • timothy
    What is the difference between internal and external environment of the body?
    7 months ago
  • Sarah
    Why does internal environment is needed to be regulated and kept in a narrow limit?
    6 months ago
  • hamid
    What is not a part of the internal environment of the human body?
    6 months ago
  • jennifer
    Why homeostasis affect the internal and external environment?
    6 months ago
  • alexa
    How does digestion and absorption maintain internal enviroment?
    6 months ago
  • belladonna
    How do monocots regulate the internal enviroment?
    6 months ago
  • Mikael
    How does disease affect homeostasis of the human body in a journal?
    5 months ago
  • Ambessa
    What structure separates the internal environment of a cell from the external enviroment?
    5 months ago
  • elizabeth
    What is internal environment in biology?
    5 months ago
  • diego
    Is the liver in contact with the external environemnt?
    5 months ago
  • Isabel
    What is the difference between extracellular fluid and internal evironment?
    5 months ago
  • YORDA
    What is the difference between human body environment and seawater components?
    4 months ago
  • sayid
    How body systems function together to maintain homeostasis?
    4 months ago
  • dawit petros
    Which 2 dy system is responsible to control responses to internal and external environments?
    4 months ago
  • linda
    IS THE RELATIVE CONSISTENCY OF THE BODY'S INTERNAL ENVIRONMENT?
    3 months ago
  • debra
    Is the chemical environment part of the external environment?
    3 months ago
  • fulvus
    What are organ responsible for regulations of internal environment?
    3 months ago
  • frank
    How does the sliding filament relate to homeostasis?
    3 months ago
  • alfredo
    How do the human body systems respond to changes in the external environment?
    3 months ago
  • amaranth
    Why is ecf is called intenal environment?
    3 months ago
  • margaret
    Is the extracellular environment your organs?
    3 months ago
  • daniel
    WHICH STRUCTURE IN AMOEBA HAS A HOMEOSTATIC FUNCTION?
    3 months ago
  • Libera
    How does the lungs help maintain a constant internal environment?
    2 months ago
  • ceredic
    What fluids make up the body's internal environment?
    1 month ago
  • sointu
    How do lungs help in the maintenance of constant internal environment?
    1 month ago
  • GALILEO
    What makes up man internal environment in an organism?
    22 days ago
  • Karin Meister
    What are the organs in the body that response to change in immediate environment?
    21 days ago
  • Annett
    How body regulates change in external environments?
    20 days ago

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