2. Homeostasis

3. Homeostasis is like your home’s thermostat Thermostat’s set point is 75ºF Inside temperature = heat 72ºF73ºF74ºF75ºF

4. Definition: The body maintains a constant internal environment Importance: Body processes work best in specific conditions

5. Control System Sensors – Gather information about the internal and external environment Ex: pressure sensors in your foot Communication system – impulse (message) sent through the body Ex: nerves connected from foot to brain. Control Center – Interprets sensory information Ex: Brain interprets pain in foot. Targets – Body part that receives the final message Ex: Muscles in foot, muscles in jaw !*%!?%&#

6. Negative Feedback Loops Reverses any change that moves conditions from a set point – Ex: if your temp drops…you will shiver to reverse that 98.6 98.498.197.797.597.296.897.297.597.798.198.498.6

7. Negative Feedback Loops Reverses any change that moves conditions from a set point – Ex: if your temp drops…you will shiver to reverse that – Ex: If your temp rises…you will sweat to reverse that 98.6 98.899.299.599.7100.199.799.599.298.898.6

8. Negative Feedback Loop: Cold Response

9. Positive Feedback Loop Increases the changes away from set points Important when rapid change is needed Ex: Pregnancy contractions – Uterus contractions begin slowly – Oxytocin released to speed up the contractions

10. More examples… Growth hormones stimulate cell division Torn vessel stimulates release of clotting factors platelets fibrin white blood cell red blood cell blood vessel clot Positive Feedback Loop 9

11. Working Together Thermoregulation: Maintenance of body temperature – Skin (sensors): sensors detect cold – Nervous system (communication system): electrical impulse sent to brain – Hypothalmus in brain (control center): releases hormones into blood stream – Muscles (target) : Hormones cause shivering

12. Some disruptions are temporary – Infections, fever, sore throats, muscle soreness Some disruptions are too great for your body to control – Frost bite: Sensors are destroyed – Paralysis: Messages from brain can’t reach target – Can lead to death Beck Weathers, thought to be dead, survived a night exposed to Mt. Everest cold. Homeostasis disruption

13. Diabetes: inability to control blood sugar Normally – Glucose in blood rises after meals – Pancreas releases insulin – Cells remove the glucose Type 1 – Immune system destroys pancreas cells – Pancreas unable to make insulin – Blood pH decreases as glucose builds up Type 2 – Pancreas does not make enough insulin – Blood pH decreases as glucose builds up insulin glucose insulin glucose

14. Review 1)Define homeostasis. 2)Name and describe the four parts of the “control system.” 3)What is negative feedback? 4)What is positive feedback? 5)Is the following example positive or negative feedback? During heavy exercise your body loses water when you sweat. As a result of water loss, your body redirects the remaining water inside your body to vital parts of your body to replenish these vital organs. 6)What is diabetes? 7)How does Type I and Type II diabetes differ?