Negative feedback loops are cycles that stop the process from continuing once the outcome reaches the desired level. Examples given include checking grades in class and improving performance, becoming hydrated and stopping thirst, and body processes like regulating blood glucose and red blood cell production that maintain homeostasis. Positive feedback loops differ in that the outcome reinforces and strengthens the cycle.

1. Feedback Loops

2. What is a negative feedback loop?
A negative feedback loop is a cycle where the final
outcome stops the whole cycle from continuing any
more.

3. Negative Feedback Loops – Real Life Example:
1) You go to AVID class.
2) Mrs. Cabrera makes you check your grades.
3) You realize you are failing 2 classes.
4) You start to work harder and ask your teachers for
missing assignments and make up work.
5) You grades go up.
6) You stop worrying about missing assignments and
make up work.

4. Negative Feedback Loops – Real Life Example:
1) You get dehydrated.
2) Your brain tells you you’re thirsty.
3) You drink water.
4) You body becomes hydrated (has enough water)
again.
5) Your brain stops telling you you’re thirsty.
6) You no longer feel thirsty, so you stop drinking.

5. Processing Piece: Are each of the following
examples of negative feedback loops?
1. A person realizes they have gained 20 pounds and
starts dieting until they are back to normal.
2. When you feel tired, you sleep until you don’t feel the
need to sleep anymore.
3. If your blood sugar gets too high, your body releases
insulin until it drops to a normal level.
4. You’re driving and your car starts drifting right when
it’s not supposed to. You turn the steering wheel left
until your car is back in the lane where it’s supposed
to be.
5. You’re running the mile. Even though you feel tired,
you make yourself keep running.

6. What are some examples of negative
feedback loops in the body?
Erythropoiesis (producing red blood cells):
1. Level of oxygen in blood gets too low.
2. Kidney notices oxygen in the blood is too low.
3. Kidney sends a hormone signal to bone marrow.
4. Bone marrow produces more blood cells.
5. Thanks to the new red blood cells, there is more
oxygen in the blood now, so the body stops making
new blood cells.

7. What are examples of negative feedback loops in the body?
Blood glucose control - insulin:
1. Blood glucose (sugar) gets too high.
2. Pancreas notices blood glucose is too high.
3. Pancreas releases more insulin.
4. Insulin travels to skeletal muscle, liver, and fat
cells.
5. Insulin makes these cells store glucose (a
monomer) as glycogen (a polymer).
6. Blood glucose goes down, so the pancreas stops
making insulin.

8. Processing Piece:
• Draw a picture to illustrate this process.

9. What are examples of negative feedback loops in the body?
Blood glucose control - glucagon:
1. Blood glucose (sugar) gets too low.
2. Pancreas notices blood glucose is too low.
3. Pancreas releases more glucagon.
4. Glucagon travels to skeletal muscle, liver, and fat
cells.
5. Glucagon makes these cells break down glycogen
(a polymer) to produce glucose (a monomer).
6. Blood glucose goes down, so the pancreas stops
making glucagon.

10. Why are negative feedback loops so helpful?
• Negative feedback loops help the body maintain
homeostasis.
• If something goes out of balance, the body reverses
it, until it gets back to normal.

11. What is a positive feedback loop?
• A positive feedback loop is a cycle where the final
outcome of a series of reactions makes the whole
cycle happen even more.

12. What is an example of a positive feedback loop?
• Childbirth:
– Oxytocin is released.
– This stimulates (increases) contractions.
– Contractions make the body release more oxytocin.
– More oxytocin stimulates even more contractions.

13. Exit Ticket
1. Using COMPLETE SENTENCES, describe an example
of a negative feedback loop. BE DETAILED.
2. In a COMPLETE SENTENCE, explain why negative
feedback loops are important.