Negative feedback systems in the human body
By Karyn Coulon
Masconomet Regional High School
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

http://en.wikipedia.org/wiki/File:Tightrope_artist_Cologne_1.jpg
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Process that occurs in all living things
All organ systems work together to achieve homeostasis
 Ability of an organism to maintain its internal environment, despite changes to its internal or external environment
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

 Feedback pathways
 A cellular relay race!
 Specific organs and structures must communicate with each other in response to changes in the body http://en.wikipedia.org/wiki/File:Southern_12_stage-02_1988.jpg
 Keeps levels of certain processes within a normal range
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

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Body Temperature
Blood pressure
Blood pH
O
2 and CO
2 concentration
Osmoregulation-Water balance
Blood glucose
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

 Stimulus
 Receptor
 Integrating center
 Effector
 Response
 Reverses the stimulus
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

 Way in which most homeostatic mechanisms work
 The product of the pathway inhibits, or shuts down, the original signal
 Why is this an important feature in living things?
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

 Allows baseline to be regained
 Conserves resources
 Cellular Materials
 Energy (ATP)
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

mouth
Stomach
Sm. Intestine
Circulatory Runners
Target cells-
Muscle
Target cells-
Brain
Target cells-
Liver
Pancreas
Game set-up
ß-cells
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
http://commons.wikimedia.org/wiki/File:Pictgram_running_man.svg
http://en.wikipedia.org/wiki/File:Archery_Target_80cm.svg
http://en.wikipedia.org/wiki/File:Llave_bronce.jpg
http://commons.wikimedia.org/wiki/File:Day-template.svg
http://commons.wikimedia.org/wiki/File:Icon_announcer.svg

mouth
Stomach
Sm. Intestine
Circulatory Runners
Target cells-
Muscle
Target cells-
Brain
Target cells-
Liver
“Glucose!! Release the insulin!”
ß-cells
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
Pancreas
Lots of glucose circulating, so
Pancreas calls out for insulin http://commons.wikimedia.org/wiki/File:Pictgram_running_man.svg
http://en.wikipedia.org/wiki/File:Archery_Target_80cm.svg
http://en.wikipedia.org/wiki/File:Llave_bronce.jpg
http://commons.wikimedia.org/wiki/File:Day-template.svg
http://commons.wikimedia.org/wiki/File:Icon_announcer.svg

mouth
Stomach
Sm. Intestine
Circulatory Runners
Target cells-
Muscle
Target cells-
Brain
Target cells-
Liver
“Glucose!! Release the insulin!”
ß-cells
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
Pancreas
Insulin has been passed to the target cells. Targets can now receive glucose.
http://commons.wikimedia.org/wiki/File:Pictgram_running_man.svg
http://en.wikipedia.org/wiki/File:Archery_Target_80cm.svg
http://en.wikipedia.org/wiki/File:Llave_bronce.jpg
http://commons.wikimedia.org/wiki/File:Day-template.svg
http://commons.wikimedia.org/wiki/File:Icon_announcer.svg

mouth
Stomach
Sm. Intestine
Circulatory Runners
Target cells-
Muscle
Target cells-
Brain
Target cells-
Liver
“Hold insulin production”
ß-cells
Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.
Pancreas
Pancreas stops insulin from being passed once there is no more glucose circulating http://commons.wikimedia.org/wiki/File:Pictgram_running_man.svg
http://en.wikipedia.org/wiki/File:Archery_Target_80cm.svg
http://en.wikipedia.org/wiki/File:Llave_bronce.jpg
http://commons.wikimedia.org/wiki/File:Day-template.svg
http://commons.wikimedia.org/wiki/File:Icon_announcer.svg

What goes up, must come down!
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Insulin
Produced by
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-cells of the Pancreas
Released into circulatory system when blood glucose is high
Facilitates the transport of glucose into target cells
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Glucagon
Produced by
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-cells of the pancreas
Released into the circulatory system when blood glucose is low
Signals the liver to break down glycogen into simple glucose
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

What goes up, must come down!
Thermoregulation
Sweating (cooling) vs. shivering (warming)
Blood Pressure
Vasconstriction vs. vasodilation
Osmoregulation
Hypotonic vs. hypertonic
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.

 On average, how many organ systems are involved in each of the processes we’ve explored?
 Are there any organ systems that you see in all of these processes?
 What might happen to these pathways if just one system was not functioning properly?
Life Sciences-HHMI Outreach.
Copyright 2009 President and Fellows of Harvard College.