Section 28-2 Homeostasis Section 28-2 Homeostasis Write everything that is underlined.

Section 28-2Section 28-2“Homeostasis“Homeostasis””

Write everything that isWrite everything that is

underlinedunderlined

28.2 Mechanisms of Homeostasis

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

28.2 Mechanisms of Homeostasis

I. HomeostasisI. HomeostasisConditions within the body must remain within Conditions within the body must remain within a narrow range – like your body temperaturea narrow range – like your body temperature

a. Homeostasis involves keeping the a. Homeostasis involves keeping the internal environment within set rangesinternal environment within set ranges

28.2 Mechanisms of Homeostasis

b. Control systems help maintain b. Control systems help maintain homeostasishomeostasis. . –sensors gather datasensors gather data

–control center receives control center receives data, sends messages data, sends messages

–communication system communication system delivers messages to delivers messages to target organs, tissuestarget organs, tissues

– targets respond to targets respond to changechange

pore

sweat glands

hairfolliclemuscle

goosebump

28.2 Mechanisms of Homeostasis

II. Feedback LoopsII. Feedback Loopsa. Negative feedback loops are a. Negative feedback loops are

necessary for homeostasisnecessary for homeostasis • Feedback compares current Feedback compares current

conditions to set ranges.conditions to set ranges.

• Negative feedback stops the Negative feedback stops the changechange

28.2 Mechanisms of Homeostasis

b. Negative Feedback Loop Exampleb. Negative Feedback Loop Example::

Holding Holding breath, breath, COCO2 2 levels levels

riserise

Control system Control system forces exhale, forces exhale, inhaleinhale

OO2 2 // COCO2 2 level level

returns to normalreturns to normal

28.2 Mechanisms of Homeostasis

c. Positive feedback increases change c. Positive feedback increases change –Example: Torn blood vessel Example: Torn blood vessel

stimulates release of clotting factorsstimulates release of clotting factors

–growth hormones stimulate cell growth hormones stimulate cell divisiondivision

platelets

fibrin

white blood cellred blood cell

blood vessel

clot