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

KEY CONCEPT Systems interact to maintain homeostasis.

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.

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

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

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