1. Homeostasis & Immune System
Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Mechanism, Thermostat
Homeostasis & Immune System
Negative Feedback
Homeostasis & disease
Immune System:
Inflammatory response
Antibody response
Cell mediated response
Allergies, AIDS, vaccination, antibiotics

2. Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Mechanism, Thermostat
Do Now:
It is winter and the temperature in your classroom has dropped to 60ºF, low below 70ºF to which the
thermostat is set. The electrician advised you that the thermostat was not working.
Explain how does the thermostat work to regulate
the temperature of the room
Temperature decreases outdoors.
2. Thermometer registers temperature
decrease inside
3. Thermostat calls the furnace for heat
4. Furnace generates heat
5. Temperature increases inside
6. Temperature reaches the thermostat
setting
7. Thermostat does not call the furnace
for heat
8. Furnace stops generating heat
9. Temperature decreases inside
Temperature _______ outdoors.
2. Thermometer registers temperature
decrease inside
3. Thermostat ____ the furnace for ____
4. Furnace generates _____
5. Temperature ______ inside
6. Temperature _______ the thermostat
setting
7. Thermostat ________ the furnace
for heat
8. Furnace _____ generating heat
9. Temperature _______ inside

3. Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Mechanism, Thermostat
Your body´s “thermostat” is set at 98ºF (37ºC).
How is this temperature maintained when you are in very hot or cold environment.
Temperature __________ outdoors.
2. ________ registers body temperature
3. ________ calls the __________ for heat
4. _________ shiver and generate heat
5. Body temperature ___________
6. Body temperature reaches the ______
7. ______ does not call the________ for heat
8. Muscles stop ____________________
9. Body temperature ________________
decreases
Skin
Brain
muscles
Muscles
increases
setting
Brain
muscles
shivering
decreases

4. Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Mechanism
During exercise the CO2 level increases.
2. Heart registers CO2 increase in blood
3. Brain calls the respiratory muscles to speed up
4. Respiration rate increases
5. CO2 level decreases in blood
6. Heart detects CO2 decrease
7. Brain call the respiratory muscles to slow down
8. Respiratory rate decreases
9. CO2 increases in blood

5. How Does Homeostasis Work in Plants?
Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Mechanism, Stoma, Guard Cells
How Does Homeostasis Work in Plants?
Plants keep their stomata open just enough to allow photosynthesis to take place but not so much that they lose an excessive amount of water.

6. How Does Homeostasis Work in Plants?
Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Mechanism, Stoma, Guard Cells
How Does Homeostasis Work in Plants?
1. Which gases do get into stomata?
2. Which gases do get out from stomata?
3. What requirements does a plant need to carry out photosynthesis?
4. How are leaf pores when plant carries out photosynthesis? Why?
5. How are leaf pores when plant doesn’t carry out photosynthesis? Why?
6. State one problem for plant that would result from a malfunction of
its stomata.
7. When the guard cells lose water, the stomata are
8. When the guard cells are swollen with water the stomata are
Carbon Dioxide CO2
Oxygen O2, Water Vapor H2O(v)
Carbon dioxide, water, and sunlight
Leaf pores are open. Guard cells are filled up with water
Leaf pores are closed. Guard cells shrink because the lack of water
The plant would not carry out photosynthesis and eventually would die
closed
open

7. How Does Homeostasis Work in Plants?
Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Mechanism, Stoma
How Does Homeostasis Work in Plants?
9. How are leaf pores of stomata when the sun is shining and water is available in the soil:
10. How are leaf pores of stomata when photosynthesis is carrying out and the air is warm:
11. Which picture represents how are leaf pores of stomata
a) when air is hot and dry:
b) when photosynthesis slows down:
c) when little water is available from the soil:
d) when photosynthesis is active:
e) at night:
12. What factor regulates the opening and closing of stomata?
13. Why do plants regulate the opening and closing of their stomata? Which is the function of stomata?
open
open
closed
closed
open
open
closed
The presence of water
To control the exchange of gases and the performance of photosynthesis

8. Objective: Understand What a Negative Feedback Look Like Key Words: Homeostasis, Negative Feedback, Insulin, Glucagon, Dynamic Equilibrium

9. Objective: Understand What a Negative Feedback Look Like Key Words: Homeostasis, Negative Feedback, Insulin, Glucagon, Dynamic Equilibrium
 1. The role of insulin is
2. The role of glucagon is 
3. The line graph is an example of  
4. Both, glucagon and insulin, are hormones that work together to
To take glucose out of the bloodstream and store it in the liver an muscles.
To decrease the glucose level in blood.
To promote the breakdown of glycogen into glucose.
To increase the glucose level in blood.
Homeostasis
Negative feedback
Dynamic Equilibrium
To maintain a constant glucose level in blood

10. Objective: Understand What a Negative Feedback Look Like Key Words: Homeostasis, Negative Feedback, Insulin, Glucagon, Dynamic Equilibrium
The results of blood tests for two individuals are shown in the data table below. The blood glucose level before breakfast is normally 80–90 mg/100 mL of blood. A blood glucose level above 110 mg/100 mL of blood indicates a failure in a feedback mechanism.
Injection of chemical X, a chemical normally produced in the body, may be required to correct this problem.

11. Objective: Understand What a Negative Feedback Look Like Key Words: Homeostasis, Negative Feedback, Insulin, Glucagon, Dynamic Equilibrium
State a title for the graph:
Identify chemical X.
Which individuals will most likely need injections of chemical X?
Explain your answer
State one reason for the change in blood glucose level between 7:00 a.m. and 8:00 a.m.
What term refers to the relatively constant level of blood glucose of individual 1 between 9:00 a.m. and 11:00 a.m.?
Glucose level in blood between 7 am to 11 am
Insulin
Individual #2 because he/she does not produce insulin
They had breakfast.
Homeostasis
Dynamic equilibrium.

12. Objective: Understand What a Negative Feedback Look Like Key Words: Homeostasis, Negative Feedback, Insulin, Glucagon, Dynamic Equilibrium
1. How do you explain what a negative feedback is?
2. You are doing some exercise. Explain how your body maintains the balance of
CO2 level in blood.
3. Give a few examples of negative feedback in living things
A negative feedback is a process that control and maintain stable the vital signs
During exercise CO2 level increases in blood. The body speed up the respiration rate in order to release more CO2 and decreases the CO2 level
Keeping body temperature near 98 F
Balance CO2 level in blood
Exchange of gases and photosynthesis in plants
Maintenance of glucose level in blood
Maintenance of calcium level in blood

13. Objective: Understand What a Negative Feedback Look Like Key Words: Homeostasis, Negative Feedback, Insulin, Glucagon, Dynamic Equilibrium
Fill in the blanks of the following paragraph. Use the words on the list. The same word can be use more than once.
 Glucose, glucagon ,fat, increase, skeletal muscles, decrease, insulin, liver,
For those who ate breakfast or lunch today, blood glucose levels _____________after eating.
The pancreas releases ______________.
Insulin stimulates cells throughout the body to take ________ out of the bloodstream.
Glucose taken out of the circulation is stored in __________ and ____________________, or converted to _______.
Within one or two hours after eating, the level of blood glucose ______________
Then, pancreas releases ______________.
Glucagon stimulates the cells of the _________ and skeletal muscles to break down complex sugar and increase ____________ levels in the blood.
Glucagon also causes fat cells to break down fats so that they can be used for the production of ________________.
increases
insulin
glucose
liver
skeletal muscles
fat
decreases
glucagon
liver
glucose
glucose

14. Objective: Understand How a Negative Feedback Mechanism Works Key Words: Homeostasis, Feedback, Parathyroid, Thyroid, PTH, Calcitonin
When blood calcium levels are too high, the (gland) _________ secretes (hormone) _________.
(Hormone) _______________ stimulates calcium deposition in the bones. Therefore, calcium leves in blood (increases /decreases) ______________.
If calcium levels drop too low, the (gland) ________________ secretes (hormone) _____________.
(Hormone) ________________ stimulates bone cells to release some of the calcium store in bone into the bloodstream.
Then, calcium level in blood (increases /decreases) _____________.
thyroid
calcitonin
calcitonin
decreases
parathyroid
PTH
PTH
increases

15. Objective: Understand What a Negative Feedback is Key Words: Homeostasis, Feedback, Mechanism, Dynamic Equilibrium
1.- What is homeostasis?
2.- What is another word for “homeostasis”?  
3.- Why is homeostasis constantly threatened?
4.- Explain how does an organism maintain homeostasis?
5.- As an example of maintaining homeostasis, how do organisms readjust body temperature?
6.- Draw a graph that shows a regular pattern of body temperature. Explain what that graph means related to homeostasis.
7.- Describe what is “dynamic equilibrium”.
8.- What can interfere with homeostasis or dynamic equilibrium?
Homeostasis is a state of balance in the body.
Dynamic equilibrium
Because the organism’s external an internal environment is constantly changing
The organism detects changes in the environment and respond with an action
that return the organism’s system to normal
If temperature is above normal the body sweats,
if temperature is below normal the muscles shake
The constant small corrections that keep the internal environment within the limits needed for survival
Microorganism and diseases

16. Examples of Feedback Mechanisms to Maintain Homeostasis
Objective: Understand What a Negative Feedback is Key Words: Homeostasis, Feedback, Mechanism, Dynamic Equilibrium
Examples of Feedback Mechanisms to Maintain Homeostasis

17. List 3 examples of negative feedbacks in living things
Objective: Understand How a Negative Feedback Mechanism works Key Words: Feedback, Mechanism, Dynamic Equilibrium, Homeostasis
Do Now:
List 3 examples of negative feedbacks in living things
How stomata regulate photosynthesis
How our body regulates CO2 levels in blood
How our body regulates a steady body temperature
How a thermostat regulates temperature in a building

18. What Is Homeostasis? Biology, pages 895-896
Objective: Understand How a Negative Feedback Mechanism works Key Words: Feedback, Mechanism, Dynamic Equilibrium, Homeostasis
What Is Homeostasis? Biology, pages
Read pages 895 and 896 on the Biology book and answer the questions below.
What is homeostasis:
2. The process in which a stimulus produces a response that opposes the original stimulus is referred to as
3. Fill in the missing label in the diagram to show how a thermostat uses feedback inhibition to maintain a stable temperature in a house
The process by which organisms keep internal conditions relatively constant
despite change in the external environment.
Negative feedback
Thermostat senses temperature change and switches off heating system
Thermostat senses temperature change and switches on heating system

19. Objective: Understand How a Negative Feedback Mechanism works Key Words: Feedback, Mechanism, Dynamic Equilibrium, Homeostasis
4. Is the following sentence true or false? The part of the brain that monitors and controls body temperature is the hypothalamus.
5. The process of maintaining a controlled, stable internal environment is called
6. What happens if nerve cells sense that the core body temperature has dropped below 37 C?
7. What happens if the body temperature rises too far above 37 C?
True
Homeostasis or dynamic equilibrium
The hypothalamus produces chemicals that signal cells throughout the body
to speed up their activities and produce heat
The hypothalamus slow down cellular activities, minimizing the production of heat