The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules; 10A describe the interactions that occur among systems that perform the functions of regulation, nutrient absorption, reproduction, and defense from injury or illness in animals; 11A describe the role of internal feedback mechanisms in the maintenance of homeostasis

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

Conditions within the body must remain within a narrow range. Homeostasis involves keeping the internal environment within set ranges.

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

Negative feedback loops are necessary for homeostasis. Feedback compares current conditions to set ranges. Negative feedback counteracts change. Negative Feedback Loop O2 / CO2 level returns to normal Holding breath, CO2 levels rise, Control system forces exhale, inhale

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