Section 28-2 “Homeostasis” Write everything that is underlined

KEY CONCEPT Homeostasis is the regulation and maintenance of the internal environment of the body

I. Homeostasis Conditions within the body must remain within a narrow range – like your body temperature a. Homeostasis involves keeping the internal environment within set ranges

control center receives data, sends messages b. Control systems help maintain homeostasis. pore sweat glands hair follicle muscle goose bump sensors gather data control center receives data, sends messages communication system delivers messages to target organs, tissues targets respond to change

II. Feedback Loops a. Negative feedback loops are necessary for homeostasis Feedback compares current conditions to set ranges. Negative feedback stops the change

b. Negative Feedback Loop Example: O2 / CO2 level returns to normal Holding breath, CO2 levels rise Control system forces exhale, inhale

growth hormones stimulate cell division c. Positive feedback increases change Example: Torn blood vessel stimulates release of clotting factors platelets fibrin white blood cell red blood cell blood vessel clot growth hormones stimulate cell division