Negative and Positive feedback systems in the human body How does your body work to maintain equilibrium in all of its cells? Homeostasis Negative and Positive feedback systems in the human body (Adapted from Lesson By Karyn Coulon) Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

What is homeostasis? 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 http://en.wikipedia.org/wiki/File:Tightrope_artist_Cologne_1.jpg Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

How does homeostasis work? Feedback pathways A cellular relay race! Specific organs and structures must communicate with each other in response to changes in the body Keeps levels of certain processes within a normal range http://en.wikipedia.org/wiki/File:Southern_12_stage-02_1988.jpg Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

Control Center (Integration Center) – compares conditions to set point Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

Positive Feedback: Negative Feedback: Response from effector reinforces or exaggerates the stimulus Very rare Negative Feedback: Response from effector decreases or inhibits stimulus

How is a home heating system an example of a feedback loop? One example of a feedback system is a thermostat connected to a furnace. The thermostat compares the temperature of the air in the room to a pre-determined setting. If the temperature in the room is below that ideal setting, the thermostat signals the furnace to send warmer air into the room. When the air in the room becomes warmer than the desired temperature, the thermostat stops signaling the furnace. The furnace switches off. If the air in the room grows cool again, the furnace switches on. The cycle repeats indefinitely, as information about the system’s status is constantly fed back into the system. Because of their cyclical nature, feedback systems are often referred to as feedback loops.

Identify the following components in a home heating system: Receptor: Stimulus: Integrating center: Effector: Response: Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

Identify the following components in a home heating system: Receptor: Sensors in thermostat Stimulus: Heat Integrating center: Thermostat Effector: Furnace Response: Furnace turned on to produce heat OR turned off Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

What things in your body need to be kept within a range? Body Temperature Blood pressure Blood pH O2 and CO2 concentration Osmoregulation-Water balance Blood glucose Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

Homeostasis Flowcharts Flowchart must include: Stimulus Receptor Set Point Integrating Center Effector Response Type of Feedback (Positive or Negative)

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Cellular Relay Race Stimulus Receptor Integrating center Effector Response Reverses the stimulus Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

Why is feedback important in living things? Allows baseline to be regained Conserves resources Cellular Materials Energy (ATP) Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

all images generated by Microsoft Clip Art Gallery mouth Stomach Sm. Intestine Circulatory Runners Target cells- Brain Target cells-Muscle Target cells- Liver Pancreas Game set-up ß-cells http://en.wikipedia.org/wiki/File:Archery_Target_80cm.svg http://commons.wikimedia.org/wiki/File:Pictgram_running_man.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 Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

“Glucose!! Release the insulin!” mouth Stomach Sm. Intestine Circulatory Runners Target cells- Brain Target cells-Muscle Target cells- Liver “Glucose!! Release the insulin!” Pancreas Lots of glucose circulating, so Pancreas calls out for insulin ß-cells 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 Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

“Glucose!! Release the insulin!” mouth Stomach Sm. Intestine Circulatory Runners Target cells- Brain Target cells-Muscle Target cells- Liver “Glucose!! Release the insulin!” Pancreas Insulin has been passed to the target cells. Targets can now receive glucose. ß-cells 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 Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

“Hold insulin production” mouth Stomach Sm. Intestine Circulatory Runners Target cells- Brain Target cells-Muscle Target cells- Liver “Hold insulin production” Pancreas stops insulin from being passed once there is no more glucose circulating Pancreas ß-cells 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 Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. all images generated by Microsoft Clip Art Gallery

Dueling Hormones What goes up, must come down! Insulin Produced by -cells of the Pancreas Released into circulatory system when blood glucose is high Facilitates the transport of glucose into target cells Glucagon Produced by -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. all images generated by Microsoft Clip Art Gallery

Dueling Mechanisms 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. all images generated by Microsoft Clip Art Gallery

Food for thought… 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. all images generated by Microsoft Clip Art Gallery