1. Homeostasis and Feedback in the Body
Colorado Life Science 2.6: Cells, tissues, organs, and organ systems maintain relatively stable internal environments, even in the face of changing external environments

2. What is homeostasis? Process that occurs in all living things
All organ systems work together to achieve ___________.
Ability of an organism to maintain its internal environment, despite changes to its internal or ________ environment!
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3. How does homeostasis work?
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
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4. 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
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5. How Does it Work? Stimulus Receptor Integrating center Effector
Response
Reverses the stimulus
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6. Example: Consider temperature in your home….
Stimulus- low thermal energy in the room (it’s cold)
Receptor- sensor in thermostat
Integrating center- thermostat
Effector- Heater
Response- increased thermal energy (it’s warmer)

7. Negative Feedback
Also called feedback Way in which MOST homeostatic mechanisms work
Stimulus produces a response that opposes
or the original stimulus
In other words, the
product of a negative
feedback pathway inhibits
or shuts down the original
signal.

8. Negative Feedback
Stimulus

9. Negative Feedback
Living Example

10. You can think of negative feedback like dueling mechanisms- What goes up, must come down!
_______________________ Sweating (cooling) vs. shivering (warming)
Blood Pressure
Vasconstriction vs. vasodilation
Osmoregulation
Hypotonic vs. hypertonic
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11. Positive Feedback A B
Takes body out of homeostasis (which can be necessary in certain circumstances)
Stimulus causes a _________ that causes more of the stimulus

12. Positive Feedback Examples
Increase in births increases population which increases births – and so on.

13. Positive Feedback Examples in Our Body Blood clotting ______________
Injured tissue signals platelets to be activated, activated platelets produce chemical signal that activates more platelets
______________
The hormone oxytocin signals a contraction, which signals they brain to produce more oxytocin

14. Additional Examples…
Identify the following as examples of positive or negative feedback loops within the body?

15. Homeostasis & the Integumentary System
Functions of Integumentary System:
Protection
Body Temperature Regulation
Excretion
Information Gathering
Vitamin D Production

16. Homeostasis: Body Temperature Regulation
If cold, ___________ generates heat and goose bumps and constricted blood vessels help decrease the heat loss from skin
If hot, __________ blood vessels allows excess heat released from skin and sweating allows energy to leave the body

17. Body Temperature & Feedback

19. Positive or Negative?

20. Homeostasis & the Circulatory System
Function of Circulatory System
Transport Oxygen,
CO2, nutrients and waste
to and from cells, as needed

21. How the Heart Works
_________ are exchanged in the lungs (Oxygen in and Carbon Dioxide out)
Heart pumps blood from the body to the lungs and then to the rest of the body

22. Homeostasis: Blood pH Buffering System
Blood has pH of 7.4 ( )
Below 6.8 or above ______ cells stop functioning

23. Homeostasis: Blood pH & Bicarbonate Buffering System

24. Positive or Negative?

25. Lack of Sleep & Stress Levels

26. Positive or Negative?

27. Homeostasis- The Digestive & Circulatory & Endocrine Systems!
Blood Sugar Regulation!

28. Processes of the Digestive System
_________ – food into mouth
Digestion – mechanical and chemical break down – starts in mouth, continues to break down in stomach and small intestine
___________ – bloodstream absorbs nutrients in small intestine and absorbs water in large intestine
Elimination – Waste eliminated through anus

29. Homeostasis- The Digestive & Circulatory & Endocrine Systems- Blood Sugar Regulation!
Glycogen- Stored glucose (polysaccharide of glucose)
Glucagon- Hormone secreted by pancreas that _________ blood sugar (break down glycogen into glucose)
Produced by alpha-cells of the pancreas
Released into the circulatory system when blood glucose is low
Signals the liver to break down glycogen into simple glucose
Insulin- Hormone secreted by the pancreas that _________ blood sugar (glucose to glycogen)
Produced by beta-cells of the pancreas
Released into circulatory system when blood glucose is high
Facilitates the transport of glucose into target cells

30. Homeostasis & the Digestive System
Blood sugar regulation:

31. Homeostasis & the Digestive System

32. Positive or Negative?

33. 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?
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