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

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

3. 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

4. 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

5. 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

6. KEY CONCEPT Systems interact to maintain homeostasis.

7. Each organ system affects other organ systems.
An organ system must do a specific job.
Organ systems must also work together to keep the organism healthy.

8. Organ systems must also work together to keep the organism healthy.
Organ systems work together to produce Vitamin D.
Thermoregulation maintains a steady body temperature. 1 2 3 4
Skin absorbs UV light
Liver produces inactive vitamin D
Kidneys produce active vitamin D
Active vitamin D used in bones
UV light

9. A disruption of homeostasis can be harmful.
Homeostasis can be disrupted for several reasons.
sensors fail
targets do not receive messages
injury
illness

10. Short-term disruption usually causes little or no harm.
Long-term disruptions can cause more damage.
Diabetes is a serious long-term disruption of homeostasis. 1 2 3 4
Pancreas cells attacked;insulin declines
Blood glucose levels rise,
Body burns fat; blood more acidic,
Cells impaired; all organs damaged.
pancreas
fats
kidneys