1. 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

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

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

4. 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

5. 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

6. 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