1. Homeostasis & Feedback Loops

2. Homeostasis is the maintenance of a constant internal environment.
A. Homeostasis works to maintain the organism's internal environment within tolerance limits (the narrow range of conditions where cells are able to function).

3. B. Homeostasis is a self-adjusting. mechanism involving feedback
B. Homeostasis is a self-adjusting mechanism involving feedback where a response alters the internal conditions based on a stimulus.
Feedback is when the response to
a stimulus has an effect of some
kind on the original stimulus.

4. Negative feedback is a control system that helps the body maintain homeostasis by sending a signal to decrease or stop a response.
Negative feedback is the most common type.

5. Negative Feedback Examples:
a. Blood Glucose Levels:

6. b. Body
Temperature:

7. c. Blood
Pressure:

8. c. Water Level:

9. Positive feedback is a control system that sends a signal to enhance or increase a response.
Positive feedback is not very common.

10. Positive Feedback Examples:
a. Breastfeeding - a baby begins to
nurse (the stimulus) and a few drops
of milk are released. This releases
a hormone in the mother which
further stimulates the release of milk
(the response). The baby continues
to nurse, stimulating more milk
release until nursing stops.

11. b. Childbirth:

12. c. Blood clotting – an open wound
stimulates the release of platelets to
the site of the open wound.

13. Negative Feedback vs.
slows down, stops or reverses the activity
wants to return levels
back to normal
Positive Feedback
increases or continues the activity