Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Necessary Life Functions  Maintain boundaries  Movement  Locomotion  Movement of substances  Responsiveness  Ability to sense changes and react  Digestion  Break-down and absorption of nutrients

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Necessary Life Functions  Metabolism—chemical reactions within the body  Produces energy  Makes body structures  Excretion  Eliminates waste from metabolic reactions

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Necessary Life Functions  Reproduction  Produces future generation  Growth  Increases cell size and number of cells

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Survival Needs  Nutrients  Chemicals for energy and cell building  Includes carbohydrates, proteins, lipids, vitamins, and minerals  Oxygen  Required for chemical reactions

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Survival Needs  Water  60–80% of body weight  Provides for metabolic reaction  Stable body temperature  Atmospheric pressure  Must be appropriate

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Interrelationships Among Body Systems Figure 1.3

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Homeostasis  Homeostasis—maintenance of a stable internal environment  A dynamic state of equilibrium  Homeostasis is necessary for normal body functioning and to sustain life  Homeostatic imbalance  A disturbance in homeostasis resulting in disease

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 1.4, step 1a Variable (in homeostasis)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 1.4, step 1b Stimulus: Produces change in variable Variable (in homeostasis) Imbalance

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 1.4, step 2 Change detected by receptor Stimulus: Produces change in variable Receptor (sensor) Variable (in homeostasis) Imbalance

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 1.4, step 3 Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor) Variable (in homeostasis) Control center Imbalance

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 1.4, step 4 Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor) Effector Variable (in homeostasis) Output: Information sent along efferent pathway to activate Control center Imbalance

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 1.4, step 5 Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor) Effector Variable (in homeostasis) Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis Output: Information sent along efferent pathway to activate Control center Imbalance

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic controls  The body communicates through neural and hormonal control systems  Receptor  Responds to changes in the environment (stimuli)  Sends information to control center

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Maintaining Homeostasis  Control center  Determines set point  Analyzes information  Determines appropriate response  Effector  Provides a means for response to the stimulus

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Feedback Mechanisms  Negative feedback  Includes most homeostatic control mechanisms  Shuts off the original stimulus, or reduces its intensity  Works like a household thermostat

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Feedback Mechanisms  Positive feedback  Increases the original stimulus to push the variable farther  In the body this only occurs in blood clotting and during the birth of a baby