Give me some Feedback!
Homeostasis*
* Maintaining of a stable internal environment
• Homeostatic Control Mechanisms – monitors aspects of the
internal environment and corrects as needed. Variations are within
limits. There are three (3) parts:
• Receptor - provides information about the stimuli
• Control Center - tells what a particular value should be
(called the set point)
• Effector - elicits responses that change conditions in the
internal environment
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Homeostatic Control Mechanisms
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control center
(set point)
Receptors
Stimulus
(Change occurs
in internal
environment.)
(Change is compared
to the set point.)
Effectors
(muscles or glands)
Response
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(Change is corrected.)
Homeostatic Control Mechanisms
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control center
The hypothalamus
detects the deviation
from the set point and
signals effector organs.
Receptors
Thermoreceptors
send signals to the
control center.
Stimulus
Body temperature
rises above normal.
Effectors
Skin blood vessels
dilate and sweat glands
secrete.
Response
Body heat is lost to
surroundings, temperature
drops toward normal.
too high
Normal body
temperature
37°C (98.6°F)
too low
Stimulus
Body temperature
drops below normal.
Receptors
Thermoreceptors
send signals to the
control center.
Response
Body heat is conserved,
temperature rises toward normal.
Effectors
Skin blood
vessels constrict
and sweat glands
remain inactive.
Control center
The hypothalamus
detects the deviation
from the set point and
signals effector organs.
Effectors
Muscle
activity
generates
body heat.
If body temperature
continues to drop,
control center signals
muscles to contract
Involuntarily.
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Homeostatic Control Mechanisms
• There are two (2) types:
• Negative feedback mechanisms
• Positive feedback mechanisms
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Homeostatic Control Mechanisms
Negative feedback summary:
• Prevents sudden, severe changes in the body
• Corrects the set point
• Causes opposite of bodily disruption to occur, i.e. the ‘negative’
• Most common type of feedback loop
• Examples: body temperature, blood pressure & glucose regulation
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Homeostatic Control Mechanisms
Positive feedback summary:
• Increases (accelerates) the actions of the body
• short-lived
• do not require continuous adjustments
•Produces more instability and chaos in the body
•Controls only infrequent events that do not require continuous
adjustments.
• Examples: blood clotting and child birth
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Animation: Positive and Negative Feedback
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