Control of the Internal Environment Chapter 2 Control of the Internal Environment

Homeostasis: Dynamic Constancy Maintenance of a constant or unchanging “normal” internal environment Few / mild demands so few responses

Homeostasis: Dynamic Constancy Steady state Constant internal environment, but not necessarily “normal” Balance achieved between demands placed on body and the response to those demands

Some Examples:

Changes in Blood Pressure at Rest

Changes in Body Core Temperature During Exercise

What controls the system?

Biological Control Systems Series of interconnected components that serve to maintain a physical or chemical parameter near normal Receptor Capable of detecting changes Integrating center Assesses input and initiates response Effector Corrects changes to internal environment

Nature of Control Systems Most control systems act via negative feedback Response reverses the initial disturbance in homeostasis

Components of a Biological Control System

Regulation of Room Temperature: a Non-Biological Control System

Example of Homeostatic Control: Regulation of Blood Pressure Stimulus Increased blood pressure from HR Receptors Baroreceptors in carotid arteries and aorta Integrating center Medulla of the brain Effector Heart Response Decreased blood pumped from heart

Example of Homeostatic Control: Regulation of Blood Pressure

Example of Homeostatic Control: Regulation of Blood Glucose

Nature of Control Systems Gain of the system Degree to which the control system maintains homeostasis System with large gain is more capable of maintaining homeostasis Large gain = narrow limits Small gain = wide limits

Example of Homeostatic Control: Regulation of Blood Glucose

Questions?

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