INTRODUCTION TO PHYSIOLOGY

Instructor’s Manual Fundamentals of Human Physiology

FORTH EDITION

Lauralee Sherwood 1 / 4

Chapter 1 Introduction to Physiology and Homeostasis

CHAPTER OUTLINE

INTRODUCTION TO PHYSIOLOGY

Physiology focuses on mechanisms of action.There are two approaches to explain physiological events; one focusing on purpose, the other on why it happens 2 / 4

and functions are inseparable.

LEVELS OF ORGANIZATION IN THE BODY

The chemical level: Various atoms and molecules make up the body

The cellular level: Cells are the basic units of life.

The tissue level: Tissues are groups of cells of similar specialization.

The organ level: An organ is a unit made up of several tissue types.

The body system level: A body system is a collection of related organs.

The organism level: The body systems are packaged together into a functional whole body.

CONCEPT OF HOMEOSTASIS

The external environment is the surrounding environment in which the organism lives. Body cells are in contact with a privately maintained internal environment.Body systems maintain homeostasis, a dynamic steady state in the internal environment.

HOMEOSTATIC CONTROL SYSTEMS

Homeostatic control systems may operate locally or bodywide.Negative feedback opposes an initial change and is widely used to maintain homeostasis.Positive feedback amplifies an initial change.Disruptions in homeostasis can lead to illness and death.

LIST OF KEY TERMS

anatomy body systems cell cell differentiation connective tissue effector endocrine gland epithelial tissue exocrine gland extracellular fluid extrinsic controls feedback gland homeostasis homeostatic control system internal environment intracellular fluid intrinsic controls lumen muscle tissue negative feedback organisms organs pathophysiology physiology plasma positive feedback secretion set point tissues

LECTURE HINTS AND SUGGESTIONS

• Ask students to provide some characteristics of living versus nonliving entities.

• Use a cell model, prepared slides, and electron micrographs to show students the major components of a cell.

• Use models and/or slides to illustrate the basic tissue types.

• Use a series of steps (staircase) to illustrate the levels of increasing organizational complexity. Relate this

concept to the hierarchy of life, particularly the steps of organization that compose the organism.

• Outline hierarchy of life from atom to organism and relate the way the course will be taught. Must first

understand atoms, chemistry, cells before we can understand organs and organ systems.

• Use an anatomical model to illustrate the organs that comprise each body system.

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

• Have students give their reasons why homeostasis is important. How healthy can an organism be without

homeostasis? 3 / 4

• 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).

• Use the example of an autopilot on an airplane when discussing negative feedback. A course is set, if the plane

veers to the west, the autopilot steers the plane toward the east to bring it back on course.

Answers to Essay Questions

• Physiology is the study of the functions of living things.
• Basic cell functions include: obtaining food and oxygen, extracting energy from nutrients, eliminating wastes,

protein synthesis, controlling exchange between cells and the surrounding environment, internal cellular movement, being able to respond to changes in the surrounding environment, and reproducing.

• External environment is the environment in which an organism lives. Internal environment is the fluid that

surrounds the cell (called the extracellular fluid, or ECF), and is the fluid through which cells make exchanges.Internal environment consists of the extracellular fluid (ECF), which is composed of two distinct parts: the interstitial fluid that directly surrounds the cell, and the plasma, the fluid portion of the blood. Materials are exchanged between the plasma and interstitial fluid, and between the interstitial fluid and the intracellular fluid

(ICF).

• Homeostasis is the processes involved in maintaining a relatively stable internal environment.
• Homeostasis, by stabilizing the internal environment, is necessary for the survival of all body cells. Each cell,

through its specialized function, contributes as part of a body system to the maintenance of a stable internal environment.

• 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 temperature are also controlled by homeostasis.

• Components of a homeostatic system include the sensor, which monitors the magnitude of the variable being

controlled, and the integrator or control center, which compares the sensor's input with what is considered a normal value (known as the set point) and then sends appropriate signals to the last component of the system (know as the effector). The effector in turn brings about an appropriate change to return the system back to the set point (normal).

• Negative feedback is a process that restores a factor to normal by moving the factor in the opposite direction of

the 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.

AUDIOVISUAL AIDS

Videos/Films The following are films that may be suitable for presentation in your class. The sources for these films, which are coded by abbreviation, are provided in Appendix A.

10 Things You Need to Know about Losing Weight (shows homeostasis mechanism) FMG, 51 Min.Biochemical Balances, FHS, 10 min.

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