© 2007 McGraw-Hill Higher Education. All rights reserved. Chapter 2 Control of the Internal Environment EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6 th edition Scott K. Powers & Edward T. Howley

© 2007 McGraw-Hill Higher Education. All rights reserved. Objectives Define the terms homeostasis and steady state Diagram and discuss a biological control system Give an example of a biological control system Explain negative feedback Define what is meant by the gain of a control system

© 2007 McGraw-Hill Higher Education. All rights reserved. Homeostasis: Dynamic Constancy Homeostasis –Maintenance of a constant internal environment Steady state –Balance between the demands placed on a body and the physiological response to those demands

© 2007 McGraw-Hill Higher Education. All rights reserved. Body Core Temperature During Exercise Fig 2.2

© 2007 McGraw-Hill Higher Education. All rights reserved. Blood Pressure at Rest Fig 2.3

© 2007 McGraw-Hill Higher Education. All rights reserved. Control Systems of the Body Goal –To regulate some physiological variable at or near constant value

© 2007 McGraw-Hill Higher Education. All rights reserved. Non-Biological Control System  in room Temperature below 20 0 C Thermostat set at 20 0 C Heating System Room temperature Returns to 20 0 C ­Room Temperature Signals thermostat To turn off heat Fig 2.4

© 2007 McGraw-Hill Higher Education. All rights reserved. Biological Control Systems Series of interconnected components that serve to maintain a physical or chemical parameter at or near constant Receptor –Capable of detecting changes Integrating center –Assesses input and initiates response Effector –Corrects changes to internal environment

© 2007 McGraw-Hill Higher Education. All rights reserved. Components of a Biological Control System Fig 2.5

© 2007 McGraw-Hill Higher Education. All rights reserved. Negative Feedback Most biological control systems –Response reverses the initial disturbance in homeostasis

© 2007 McGraw-Hill Higher Education. All rights reserved. Gain of a Control System Gain of the system –Degree to which the control system maintains homeostasis –System with large gain is more capable of maintaining homeostasis

© 2007 McGraw-Hill Higher Education. All rights reserved. Example: Regulation of Blood Pressure Fig 2.6

© 2007 McGraw-Hill Higher Education. All rights reserved. Example: Regulation of Blood Glucose Fig 2.7

© 2007 McGraw-Hill Higher Education. All rights reserved. Example: Cellular Stress Response Fig 2.8

© 2007 McGraw-Hill Higher Education. All rights reserved. Exercise: A Test of Homeostatic Control Submaximal exercise in a cool environment –The body’s control systems can maintain steady state Maximal exercise or exercise in a hot/humid environment –May not be able to maintain steady state –Severe disturbances in homeostasis can occur

© 2007 McGraw-Hill Higher Education. All rights reserved. Chapter 2 Control of the Internal Environment