Download - Lecture 1 (Introduction-Homeostasis)
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LECTURE 1Control of the Internal Environment
PHYSIOLOGY OF PHYSICAL ACTIVITIES
Adapted from
Theory and Application to Fitness and Performance, 5th edition
Scott K. Powers & Edward T. HowleyPresentation revised and updated byMOHD SANI MADON (PhD)
UPSI 2011
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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
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Homeostasis: Dynamic Constancy
Homeostasis Maintenance of a constant internal
environment
Steady state Balance between demands placed on
body and the physiological response to those demands
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Body Core Temperature During Exercise
Fig 2.2
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Blood Pressure at Rest
Fig 2.3
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Control Systems of the Body
Goal To regulate some physiological variable
at or near constant value
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Non-Biological Control System in roomTemperature below 200 C
Thermostat set at 200 C
Heating System
Room temperature
Returns to 200 C
Room TemperatureSignals thermostat
To turn off heat
Fig 2.4
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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
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Components of a Biological Control System
Fig 2.5
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Negative Feedback
Most biological control systems Response reverses the initial disturbance
in homeostasis
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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
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Example:Regulation of Blood Pressure
Fig 2.6
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Example:Regulation of Blood Glucose
Fig 2.7
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Example:Cellular Stress Response
Fig 2.8
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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