Chapter1.notebook
September 22, 2016
Objectives
* Describe the concept of Homeostasis and feedback mechanisms
* Define and give examples of positive and negative feedback.
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Chapter1.notebook
September 22, 2016
Homeostasis
• Homeostasis: all body systems working
together to maintain a stable internal
environment
Systems respond to external and internal changes
to function within a normal range (set point)
ex: body temperature, heart rate, blood pressure
Vital Sign: Pulse Checking your radial pulse
> Gently place 2 fingers of your other hand on this artery. > Do not use your thumb, because it has its own pulse that you may feel. > Count the beats for 30 seconds, and then double the result to get the number of beats per minute.
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Chapter1.notebook
September 22, 2016
Homeostatic regulation ­ adjustments in physiological systems that preserve homeostasis
Negative Feedback
Positive Feedback 3
Chapter1.notebook
September 22, 2016
Feedback Mechanism (loop) Components
Stimulus: a change in the environment (internal or external)
Receptor: cell or tissue that is sensitive to a stimulus ("perceives" the change)
Control center: receives and processes information from the receptor
Effector: responds to the commands of the control center
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Chapter1.notebook
September 22, 2016
Negative Feedback
• A variation outside normal limits that
triggers an automatic response to
correct the situation.
Fig. 1.4 in your textbook
* immediate stabilization
https://www.youtube.com/watch?v=WBfHjcSB5d0
* tries to hit target set point
*regardless of the nature of the stimulus
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Chapter1.notebook
September 22, 2016
Positive Feedback
• An initial stimulus produces a response
that reinforces the normal stimulus
Fig. 1.5 in your textbook
* moves away from target set point
*usually returns to set point eventually
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Chapter1.notebook
September 22, 2016
Homeostasis
Feedback Loops
Target Set Point
Negative
Positive
Stabilization
Amplification
Ex: Body Temp
Regulation
Ex: Childbirth
Contractions
/blood clotting
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Chapter1.notebook
September 22, 2016
The Big Picture
• Homeostasis is a state of equilibrium
• Systems work together to maintain
homeostasis
• Physiological systems (feedback loops) work
to restore balance
• Failure results in disease or death
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Chapter1.notebook
September 22, 2016
Think it over...
1. Explain the function of negative feedback systems
2.Why is positive feedback helpful in labor, but unsuitable for regulation of body temp?
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