control of the internal environment chapter 2. homeostasis: dynamic constancy homeostasis...
Post on 19-Dec-2015
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Control of the Internal Environment
Chapter 2
Homeostasis: Dynamic Constancy Homeostasis
– 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?
END