BiologyUnit 3 Notes:Homeostasis &

Feedback Mechanisms

(1) Homeostasis•Homeostasis: Maintaining internal balance / stability.

•When something causes the environment inside your cells to change, there are chemical processes in place to bring the cells back to their “normal” state.

• These “Chemical Processes” are involuntary and called “Feedback Mechanisms”.

(2) Basic Homeostatic Response

“Homeostasis is a delicate balancing act.”

1. Starts with a stimulus (something that causes the change).2. A receptor (nerves) in your body detects the change.3. A nerve message is sent to the nervous system.4. A nerve message is sent out of the nervous system back to the body

part.5. The body part does something to regain its “normal” state.

(3) Negative Feedback Mechanisms

•Negative Feedback Mechanisms: Chemical processes that return your body back to its “normal” state.

•Most homeostatic responses are regulated by Negative Feedback Mechanisms.

• Examples: •Body Temperature (Shivering & Sweating)•Blood Sugar Levels (Insulin)

(4) Positive Feedback Mechanisms

•Positive Feedback Mechanisms: Chemical processes that cause more change to happen.

•Very few homeostatic responses are Positive Feedback Mechanisms.

• Examples:•Childbirth (Oxytocin & Contractions)•Blood Clotting (Platelets & Chemicals)