1. Sponge (Pg. 36)
Hypothesize how these climbers hang on to their body temperature.

2. Hypothesize how these climbers hang on to their body temperature.
His body is working inside to provide energy and to maintain a stable body temperature.

3. 28.2 Mechanisms of Homeostasis
Set up Cornell Notes on pg. 37
Topic: 28.2 Mechanisms of Homeostasis
Essential Question(s):
On the top ½ of pg. 36 please create a double-bubble comparing and contrasting Negative and Positive feedback
On the bottom ½ of pg. 36 please draw your own negative feedback loop with a real example NOT used in class
28.2 Mechanisms of Homeostasis
2.1 Atoms, Ions, and Molecules

4. KEY CONCEPT Homeostasis is the regulation and maintenance of the internal environment.

5. Homeostasis is the regulation and maintenance of the internal environment within the narrow ranges that support human life. It is a delicate balance.
Temperature
Fluids
Salts pH
nutrients

6. Conditions within the body MUST remain within a narrow range.
Homeostasis involves keeping the internal environment within set ranges.

7. Human Internal Environment
Protects our cells from external changes
Is relatively constant, despite an ever-changing outside environment (98.6 degrees)

8. How does a thermostat work?
Your control center (brain) is like a thermostat
Has a set temperature (98.6)
If it is too hot- sends signals to effectors (sweat glands) to lower body temp (ex: sweat)
If too cold- sends signals to effectors to raise body temp (ex: shiver)
How does a thermostat work?
Air conditioner
Heater

9. activated by an imbalance
Negative Feedback: The control system (brain) sends signals/instructions to effectors (muscles and glands) to stabilize the body
activated by an imbalance
corrects an imbalance, brings body back to Homeostasis
Pancreas receptors detect high blood sugar
Stimulus: rising blood sugar
The control center signals the pancreas to secrete insulin
Effector: Insulin causes liver cells to take up sugar in the blood
Response: blood sugar returns to normal= homeostasis

10. 100*
Change occurs in internal or external environment

11. Receptors
Sensors: Gather data, and Send signals to the control center

12. The brain receives data, and compares it with “set point”, sends messages to effectors

13. Work to return the body to balanced levels- delivers messages to target organs/glands

14. Targets respond to change, and body returns to homeostasis

15. Please complete a negative feedback loop for body temperature rising due to it being 110* outside

16. Real life example:
100*
Body temperature rises above 98.6 due to it being 110* outside

17. Skin sensory receptors send signals to brain

18. The hypothalamus detects the difference from the set point: 98. 6
The hypothalamus detects the difference from the set point: 98.6* and signals effectors

19. Messages sent to sweat glands

20. You sweat, body temperature lowers to normal (98.6)

21. How are negative feedback loops necessary for homeostasis?
Feedback compares current conditions to set ranges.
Negative feedback counteracts change
Keeps environment stable
Negative Feedback Loop
Holding breath, CO2 levels rise,
O2 / CO2 level returns to normal
Control system forces exhale, inhale

22. Positive Feedback: Process by which changes cause additional similar changes, producing unstable conditions- pushes away from homeostasis

23. Positive feedback increases change
Important when rapid change is needed
platelets
fibrin
white blood cell
red blood cell
blood vessel
clot
EX: Torn vessel stimulates release of clotting factors

24. At your table, please explain the difference between a negative feedback loop and positive feedback loop?
Negative feedback loop counteracts change away from set points. Positive feedback loops increases change away from set points.

25. Homeostasis is the regulation and maintenance of the internal environment within the narrow ranges that support human life.
Body temperature is normal
Normal amounts of blood and other bodily fluids
With your neighbor, please make a list of external or internal factors that would affect your body’s homeostasis.

26. Lifestyle (drinking, smoking, diet) Injury Illness (fever, infection)
Please make a list of external or internal factors that would affect your body’s homeostasis. Pg. 37
Disease
Stress
Lifestyle (drinking, smoking, diet)
Injury
Illness (fever, infection)
Dehydration/Starvation
Outside temperature

27. A disruption of homeostasis can be harmful
Sensors fail to detect changes
Wrong messages sent
Messages fail to reach their targets
Serious injuries overwhelm the body
Viruses or bacteria change the body’s internal chemistry

28. Short term effects
Last a few days or weeks
Ex: A cold virus enters your body
Within a few days your immune system begins to kill the virus

29. Long term effects
Causes long term damage to the body
Ex: diabetes

30. Homework
On the top ½ of pg. 37 draw a double-bubble map, comparing and contrasting negative and positive feedback. Make sure you give examples of each.

31. Causes additional changes stimuli
Corrects an imbalance
Causes additional changes
stimuli
Negative
Feedback
receptors
Positive
Feedback
Ex: Contractions during childbirth
Ex: temperature regulation
Control center
Moves body away from homeostasis
effectors
Returns body to homeostasis