3/30/2015
Basic Principle #4
Chapter 1
Homeostasis is essential for the survival
of all living systems
•
Homeostasis: to stay the same
•
An Introduction to the Study
of the Human Body
•
Describes the ability of the body to
establish a stable internal environment
•
Examples of critical homeostatic
systems?
Lecture 2: Homeostasis
Homeostasis
•
Parameter: any condition that can be
Homeostasis
All homeostatic systems share 3
structural elements
•
altered
•
Set point: the optimal level or
1.
acceptable range for any given
parameter
• 3 possible states for a homeostatic
system
2. Control center (or integration center) –
sends instructions to effector
3. Effector – responds to control center’s
instructions, eventually restoring
homeostasis
Normal (set point)
2. Above normal
3. Below normal
1.
•
Receptor – senses change in homeostasis
Examples in the body?
Homeostasis
Example: Thermostat
What is the…
•
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Set point?
•
Stimulus?
•
Receptor?
•
Control center?
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Signal?
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Effector?
•
Response?
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3/30/2015
Example: Thermoregulation
Example: Thermoregulation
Why is this important?
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Example: Thermoregulation
What is the…
•
•
Set point?
•
Stimulus?
•
Receptor?
•
Control center?
•
Signal?
•
Effector?
•
Response?
Homeostasis
Negative feedback: method of
•
homeostatic control where the effector
acts to eliminate the stimulus or reduce
its magnitude
Very common
•
Example: Blood Sugar Regulation
What is the…
•
Example: Blood CO2 Regulation
What is the…
•
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Set point?
•
Set point?
•
Stimulus?
•
Stimulus?
•
Receptor?
•
Receptor?
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Control center?
•
Control center?
•
Signal?
•
Signal?
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Effector?
•
Effector?
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Response?
•
Response?
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3/30/2015
Example: Blood CO2 Regulation
What happens when CO2 levels fall
below normal?
•
Homeostasis
•
Positive feedback: method of
homeostatic control where the effector
acts to exaggerate the stimulus
•
Set point?
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Stimulus?
•
Not as common
•
Receptor?
•
•
Control center?
Seen in situations where once a process
begins it must finish quickly
•
Signal?
Effector?
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Examples?
•
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Response?
Positive Feedback
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Labor and delivery
Homework #1
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Due Monday
•
Pick an example of homeostasis in the human
body (NOT from the ones discussed in class)
•
Draw a flow diagram that states and shows
the connections between the set point,
stimulus, receptor, control center, signal,
effector,, and response
effector
•
In a short paragraph (3(3-4 sentences), state
whether this system relies on positive or
negative feedback, and explain why it fits this
model
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