1. Objectives: Significance of homeostasis Positive and negative feedback

2. Disruption of Homeostasis

3. Disruption of Homeostasis

4. Disruption of Homeostasis

5. Disruption of Homeostasis
Polycystic Kidney Disease

6. Disruption of Homeostasis

9. Start here

10. Two ways to maintain homeostatis
Negative feedback
Positive feedback

11. Negative Feedback: example body temperature

12. Q1: compare response to original stimulus
Answer:
The response by the effectors is antagonistic (opposite) of the stimulus
Stimulus = body temp ↑
Response = body temp ↓

13. Q2: homeostasis restored? How do you know?
Answer
Yes, because the response counteracts the stimulus
Brings back balance

14. Positive Feedback: example labor contractions

15. Q3: compare response and stimulus in positive feedback
Answer
The response acts to heighten or increase the stimulus
Stimulus = ↑ distortion of uterus
Response= ↑ distortion and contraction of
uterus

16. Q4: Is homeostasis restored in this example? How do you know?
Answer:
No, homeostasis is continually disrupted
This is a good thing in this case b/c returning to homeostasis would cause the birthing process to stop.
The positive feedback loop will continue until birth is complete.

17. Lots of examples of negative feedback loops, few positive loops
Blood glucose – pages __295__
Blood clotting – pages __314___
Blood calcium level – pages __287____
Female reproductive cycle – pages _508___

18. About Drinking Water
One glass of water shuts down midnight hunger pangs for almost 100% of the dieters studied in a University study.
Lack of water is the #1 trigger of daytime fatigue.
9-10 glasses of water a day could significantly ease back and joint pain for up to 80% of sufferers.

19. More water stuff
A mere 2% drop in body water can trigger fuzzy short-term memory, trouble with basic math, and difficulty focusing.
Drinking 5 glasses of water daily decreases the risk of colon cancer by 45%, breast cancer by 79% and one is 50% less likely to develop bladder cancer.

20. Cellular homeostasis
Every level of organization within the body must maintain homeostasis
Phospholipid Bilayer

21. Diffusion
Diffusion is the movement of molecules from a higher concentration to a lower concentration.
The difference in concentration of two solutions is called the concentration gradient
Demonstration: food coloring in water
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22. Diffusion across membranes
Molecules that dissolve in lipids can cross the lipid bilayer through diffusion. Example: O CO H2O

23. Osmosis Think back to solutions: solutes and solvents
Osmosis is the process by which water molecules diffuse across a cell membrane from an area of lower solute concentration to an area of higher solute concentration.
Direction of movement depends on relative concentrations of solutions.

24. Direction of movement into cells
Hypotonic to the cytosol
solution outside the cell is less concentrated than inside the cell
water moves into the cell
Hypertonic to the cytosol
solution outside the cell is more concentrated than inside the cell
water moves out of the cell
Isotonic
concentrations are equal

25. What about the molecules that can’t pass through the membrane freely?
Glucose, Na+, Ca+, K+ and lots of other molecules need to get into and out of the cell but can’t get through the lipid bilayer
They must use the proteins embedded in the lipid bilayer – and this takes type of transport takes energy

26. Now apply this knowledge to come up with a logical conclusion for the homeostasis and sports drink lab
Putting it altogether: research how your body maintains homeostasis when you become dehydrated. Why do you feel thirsty?

28. Active Transport Transport Notes Active Transport Movie 1

29. Predicting water movement