28 2 Mechanisms of Homeostasis KEY CONCEPT Homeostasis

28. 2 Mechanisms of Homeostasis KEY CONCEPT Homeostasis is maintaining stable internal conditions.

28. 2 Mechanisms of Homeostasis Warm up: • List 4 systems of the body and how they help maintain homeostasis.

28. 2 Mechanisms of Homeostasis Body conditions must remain within a narrow range. Ex: body temp 96 -102 degrees F (normal range) • Homeostasis involves keeping internal conditions within normal ranges (body temp, blood p. H, blood sugar levels, etc. )

28. 2 Mechanisms of Homeostasis What happens when your body gets to hot?

28. 2 Mechanisms of Homeostasis What happens when your body gets too cold?

28. 2 Mechanisms of Homeostasis What system works to help maintain your body temperature?

28. 2 Mechanisms of Homeostasis Negative feedback loops are necessary for homeostasis. • Negative feedback counteracts change (response opposes stimulus). • The nervous system senses when the body gets too hot, and communicates signals to cool down. Negative Feedback Loop Holding breath, CO 2 levels rise O 2 / CO 2 level returns to normal Control system forces exhale, inhale

28. 2 Mechanisms of Homeostasis Which arrows show a return to normal after a negative feedback loop was activated?

28. 2 Mechanisms of Homeostasis What happens when you cut yourself and you start to bleed?

28. 2 Mechanisms of Homeostasis • Positive feedback increases change (response amplifies stimulus). Stimulus Response A Response C (more of A and B) Response B

28. 2 Mechanisms of Homeostasis Positive feedback moves the body further away from homeostasis to accomplish a goal. • Examples: – Childbirth - Oxytocin (a hormone) stimulates contractions - Contractions stimulate release of more oxytocin - Contractions increase in frequency and strength until baby is born – Blood clotting - Bleeding stimulates production of chemicals - Clotting begins, causing release of additional chemicals that accelerate clotting - Continues until bleeding stops platelets blood vessel fibrin clot red blood cell white blood cell

28. 2 Mechanisms of Homeostasis Next: • You are going to create a brochure that describes either a positive or a negative feedback loop. • You are a pharmaceutical company and you are trying to sell your product. • Make sure and include all systems that are involved in the process. • Explain how your product maintains homeostasis inside the body.