Homeostasis & Feedback Loops

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).

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.

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.

Negative Feedback Examples: a. Blood Glucose Levels:

b. Body Temperature:

c. Blood Pressure:

c. Water Level:

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

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.

b. Childbirth:

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

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