Introduction to Physiology and Homeostasis

Chapter 1 Introduction to Physiology and Homeostasis

CHAPTER OUTLINE

1.1 INTRODUCTION TO PHYSIOLOGY Physiology focuses on mechanisms of actions. Structure and function are inseparable. Obvious examples include enamel-coated teeth providing wear resistance, and hinged joints allowing the bending of a limb; less obvious examples include the interface between air and blood in the lungs, which allows for both extracting of fresh gases from the air and expelling of waste gases from the blood to the air.

1.2 LEVELS OF ORGANIZATION IN THE BODY -The chemical level: Various atoms and molecules make up the body All matter, living or non-living, is composed of atoms. Oxygen, carbon, hydrogen, and nitrogen make up approximately 96 percent of the total body chemistry. -The cellular level: Cells are the basic units of life. Cells are the least complex level of organization capable of performing the tasks of life (the basic units of life). Cellular differentiation results in approximately 200 specialized types of cells. -The tissue level: Tissues are groups of cells of similar specialization. Tissues are assemblages of cells that perform similar physiological functions. The four primary tissues are: Muscle: tissue with cells specialized for contracting; Nervous: tissue with cells specialized for initiating and transmitting electrical impulses, which most often result in the release of neurotransmitters for communicating with target cells; Epithelial: tissue with many cells arranged close together with little extracellular matrix and specialized for forming a barrier used for exchange of materials between the environment and the organism; and Connective: tissues with few cells arranged in extensive extracellular matrix specialized to support the body both anatomically and functionally. -The organ level: An organ is a unit made up of several tissue types. Organs are differentiated structures composed of two or more primary tissue types performing specific functions. Organs are composed of highly specialized forms of the primary tissues so that specific tasks can be performed. -The body system level: A body system is a collection of related organs. Body systems are collections of organs performing integrated functions in the body. The 11 body systems are: circulatory, digestive, respiratory, urinary, skeletal, muscular, integumentary, immune, nervous, endocrine, and reproductive. -The organism level: The body systems are packaged into a functional whole body. The assemblage of body systems forming a single, independently living individual.

1.3 CONCEPT OF HOMEOSTASIS Body cells are in contact with a privately maintained internal environment. Cells require homeostasis (a dynamic, steady state in the internal environment—internal milieu), and by their combined actions function to maintain homeostasis. All body systems contribute to maintaining homeostasis both locally and throughout the body.

Body systems maintain homeostasis, a dynamic steady state in the internal environment. Body cells are in direct contact with the internal environment, the fluid that directly surrounds the cells. It is through the internal environment that cells make life-sustaining exchanges with the external environment. The internal environment contains intracellular fluid, which is contained within all body cells, and extracellular fluid, which is made up of two components: interstitial fluid and plasma.

1.4 HOMEOSTATIC CONTROL SYSTEMS Homeostatic control systems may operate locally (intrinsic) or systemically (extrinsic).

Negative feedback opposes an initial change and is widely used to maintain homeostasis. Negative feedback reverses an initial change in a monitored variable, returning the system to set point.

Introduction to Physiology and Homeostasis Positive feedback amplifies an initial change in a monitored variable, culminating in an explosive return to set point. Feedforward mechanisms initiate responses in anticipation of a change.

Disruptions in homeostasis can lead to illness and death.

LIST OF KEY TERMS

Anatomy Organs -extrinsic controls Physiology Body systems -intrinsic controls Cell -circulatory Control mechanisms -intracellular fluid -digestive -feedforward Internal environment -respiratory -negative feedback -extracellular fluid -urinary -positive feedback -plasma -skeletal -controlled variable -interstitial fluid -muscular -set point Tissues -integumentary -sensor -muscle -immune -integrator/control center -nervous -nervous -effector -epithelial -endocrine -pathophysiology -connective -reproductive Secretion Organism Glands Homeostasis -exocrine -external environment -endocrine -internal environment

LECTURE HINTS AND SUGGESTIONS

1. Define functions shared by all living organisms.

2. Take extra time to help students fully understand how data can be presented. Make sure they understand how to interpret tables, and especially graphs and other visually displayed data. Have students draw various graphs of simple data emphasizing the relationships between dependent and independent variables.

3. Describe primary tissue functions. Use basic cartoons found in the chapter as illustrations. Some students could benefit from photomicrographs of actual tissue preparations.

4. Hierarchy of complexity can be illustrated using a pyramid, with blocks representing various levels of organization (e.g., beginning with atoms on the lowest level, progressing through cells, tissues, etc.) and the organism represented by the top of the pyramid.

5. Use a laboratory animal (e.g., fetal pig, rat, cat) to illustrate the various organ systems.

6. Demonstrate negative feedback (homeostasis) using a pendulum or video of a person in a canoe or kayak maintaining balance or “set point” by responding to an input by an opposite action. Each student is familiar with sweating when it’s hot and shivering when it’s cold. Exploit this to discuss homeostasis and negative feedback in actual physiological terms.

7. Use a mechanical clock as an example of nonhomeostasis as it progressively “winds down” and stops. Ask students for examples of homeostasis within the body and elsewhere in the environment (e.g., a see-saw, insulin versus glucagon, temperature control in a room or refrigerator).

8. Be sure to remind students of the learning resources available on MindTap®.

Chapter One AUDIOVISUAL AIDS

Videos/Films The following are films that may be suitable for presentation in your class. These AV aids can be found by clicking on the website listed.

http:// www.insight-media.com

Homeostasis, Item #BAY3833, 25 min. Introducing the phenomenon of homeostasis, this DVD explores homeostatic mechanisms and considers the roles of the nervous and endocrine systems in maintaining balance.

Systems of the Human Body Systems, Item #BAX3182, 51 min. This program examines the digestive, circulatory, respiratory, skeletal, muscular, nervous, endocrine, integumentary, and immune systems of fish, poultry, cattle, sheep, goats, pigs, and humans.

Elements of Biology: Cells, Item #BTS3180, 56 min. This program describes the cell membrane and examines the specialized cellular structures that perform such functions as energy production, waste disposal, synthesis of new molecules, and storage of genetic material. http://ffh.films.com/

Cells: The Building Blocks of Life, FHS, 16 min. This video takes a close-up look at the lowest common denominator of all life: the cell. It illustrates essential cellular processes—transportation of materials, communication, energy transfer, protein-building, waste disposal, movement, and the all-important mitosis and meiosis—as well as key cellular landmarks like the nucleus, ribosomes, mitochondria, Golgi complex, endoplasmic reticulum, and lysosomes. Special attention is given to recent advances in biotechnology.

Coping with Change, FHS, 10 min. This program introduces the concept of homeostasis, with a basic model of how it works. Using the example of changing temperature in the external environment and our bodies’ own internal responses, the program illustrates one way the process of homeostasis maintains a relatively balanced internal condition.

The Feedback Cycle, FHS, 10 min. This program describes the feedback cycle, the ongoing monitoring of homeostasis to inhibit or stimulate the release of hormones. The program shows how negative feedback works and the many ways the body responds to messages from receptors. The monitoring of blood temperature is used as an example.

Homeostasis, FHS, Item #5990, 20 min. In order to understand homeostasis in a natural setting, this program observes what happens to the body during a marathon race. By monitoring the various physiological responses of one of the runners, we show the many changes and adjustments being made in the body as the race progresses. The data obtained from the runners are used to explain in detail how the body regulates temperature, blood oxygen, blood glucose, water balance, heart rate, breathing rate, and hormone levels. The program provides a complete introduction to the following topics: • Homeostatic mechanisms within the body • Regulation of temperature • Regulation of blood sugar • Feedback systems

http://ffh.films.com/

Introduction to Physiology and Homeostasis Homeostasis, FHS, Item #BVL40303, 25 min. This program introduces students to the phenomenon of homeostasis, illustrating its crucial importance and how it works inside the body. Homeostatic mechanisms for detecting and counteracting changes are explored, along with the roles of the nervous and endocrine systems in maintaining a balance. Viewers will gain insight into the workings of stimulus-response pathways and the chemical and physiological factors involved. Viewable/printable educational resources are available online.

Landscapes and Interiors (Living Body Series), FHS, Item #821, 28 min. An introduction to human biology—the subject of that most fascinating human study, ourselves. The program shows a wide range of human activities, and how the body enables us to live in diverse climates and perform diverse activities. Extraordinary close-up filming over the body’s exterior and in its interior causes surface differences to fade away and enables viewers to see the immensely complex and interactive systems that constitute the living body.

Systems of the Body S.M.A.R.T. Box, Item #BVL33114, ISBN 978-0-7365-9034-1. The Systems of the Body S.M.A.R.T. Box provides teachers and students with an outstanding blend of multimedia materials designed to illustrate and explain the human body’s major systems. Correlated to Project 2061 Benchmarks for Science Literacy from the American Association for the Advancement of Science and National Health Education Standards, the S.M.A.R.T. Box combines core content, creative activities, a Teacher’s Guide with suggested lesson plans, and a Teacher’s Resource Pack to deliver an enriching and engaging learning experience. https://www4091.ssldomain.com/smavideo/Store/titledetail.cfm?MerchID=107345

Homeostasis: The Body in Balance, Item #HRM 301, 26 min. This video uses a variety of vivid examples to show how homeostasis is essential for the survival of living things. Eye-catching graphics and computer animation clarify complex biological processes. The video first looks at negative feedback systems and ways that cold-blooded and warm-blooded animals regulate their internal temperatures. The program examines how the human excretory system maintains stable levels of water and important chemicals inside the body while getting rid of poisonous wastes. The video also describes how the pancreas secretes insulin and glucagon, which maintain levels of glucose in the blood within certain critical levels.

Software A.D.A.M. Multimedia Package: Curriculum Resources, FHS, multimedia support for A&P BioTutor, IL, covers general biology including homeostasis. Body Works, LC. Delmar’s Body Structures and Functions CD, RAM, an interactive CD. Essentials of Human Physiology, EXP, an interactive CD ROM. Homeostasis, PLP, covers homeostasis as the central framework of physiology. The Human Body: An Overview, CBS, seven lessons introduce students to six human body systems. Humanscope, visible human project. Humans as Organisms, FHS, an interactive CD ROM. Interactions CD-ROM Series for Anatomy and Physiology, Exploring the Functions of the Human Body, 1.0, JW. Ultimate Human Body, DK. Your Body (Series I, II), CBS, covers all body systems.

Relevant Educational Websites http://www.physiologyeducation.org/ (Teaching Resources)

Chapter One This website offers contact with PERC members, download of free or purchased software, and access to scientific papers and abstracts. http://www.biology-online.org/4/1_physiological_homeostasis.htm (Tutorial) This is a one-page tutorial site dealing with homeostasis/feedback control. Also, other links are available for homeostasis. http://biology.about.com/cs/physiology/index.htm (General Physiology) This page is a jump-off point with several links to animations, reviews, and many illustrations of key physiological events. http://www.hapsweb.org (Human Anatomy and Physiology Society—Education) The homepage for the Human Anatomy and Physiology Society. This page has links for members and the general public. A “resources” link provides members (free to join) access to information concerning lab safety, course setup, HAPS courses for instructors, etc. http://youtube.com There are hundreds of videos on YouTube that can be used to demonstrate physiological concepts. http://www.brookscole.com/biology The text’s website offers lists of resources not found in this manual.

Relevant Organizations Providing Educational Resources American Physiological Society 9650 Rockville Pike Bethesda, MD 20814 (301) 530-7164 http://www.the-aps.org

American Association of Anatomists American Physiological Society 9650 Rockville Pike Bethesda, MD 20814-3998 http://www.anatomy.org

Howard Hughes Medical Institute 4000 Jones Bridge Road Chevy Chase, MD 20815 (301) 215-8500 http://www.hhmi.org/

Human Anatomy & Physiology Society 8816 Manchester, Suite 314 St. Louis, MO 63144 (800) 448-4277 http://www.hapsweb.org

Physiology Educational Research Consortium P.O. Box 51187 Seattle, WA 98115 http://www.physiologyeducation.org/

The Physiological Society P.O. Box 11319 London, WC1X8WQ, UK

Introduction to Physiology and Homeostasis http://www.physoc.org

Answers to End of Chapter “Understanding Concepts”

1. Physiology is the study of the functions of living things. These functions are made possible by anatomy, the structural design and relationships of the various body parts that carry out the function.

2. Basic cell functions include: obtaining food and oxygen, extracting energy from nutrients, eliminating wastes, p rotein synthesis, controlling exchange between cells and the surrounding environment, internal cellular moveme nt, being able to respond to changes in the surrounding environment, and reproducing. Internal environment is t he fluid that surrounds the cell (called the extracellular fluid, or ECF), and is the fluid through which cells make exchanges. ECF is composed of two distinct parts: the interstitial fluid that directly surrounds the cell, and the pl asma, the fluid portion of the blood. Materials are exchanged between the plasma and interstitial fluid, and betw een the interstitial fluid and the intracellular fluid (ICF). External environment is the environment in which an o rganism lives.

3. Homeostasis is the processes involved in maintaining a relatively stable internal environment. A stable internal environment is necessary for the survival of all body cells. Each cell, through its specialized function, contribute s as part of a body system to the maintenance of a stable internal environment.

4. The central theme of physiology and this textbook is that homeostasis is required by all cells, and that these sam e cells contribute to the maintenance of homeostasis. The text conveys the details of how the individual cells an d their relationships with other cells function to maintain homeostasis.

5. Factors that need to be controlled via homeostatic mechanisms include concentrations of: nutrients, oxygen and carbon dioxide, waste products, water, salts, and electrolytes. In addition, pH, volume, pressure, and temperatur e are also controlled by homeostasis.

6. Components of a homeostatic system include the sensor, which monitors the magnitude of the variable being co ntrolled, and the integrator or control center, which compares the sensor's input with what is considered a norma l value (known as the set point) and then sends appropriate signals to the last component of the system (known a s the effector). The effector, in turn, brings about an appropriate change to return the system back to the set poin t (normal).

7. Negative feedback is a process that restores a factor to normal by moving the factor in the opposite direction of t he initial change. Negative feedback is the basis for homeostasis. Positive feedback, on the other hand, enhances or amplifies the initial change and continues to drive the system in the direction of the initial change.

Chapter One