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