1. Homeostasis
Mrs. Morgan
Biology

2. Homeostasis
“Homeostasis is a term that is used to both describe the survival of organisms in an ecosystem and to describe the successful survival of cells inside of an organism. Organisms and populations can maintain homeostasis in an environment when they have a steady level of births and deaths.”

3. Negative feedback
Negative feedback is a process that happens when your systems need to slow down or completely stop a process that is happening. When you eat, food travels into your stomach, and digestion begins. You don't need your stomach working if you aren't eating. The digestive system works with a series of hormones and nervous impulses to stop and start the secretion of acids in your stomach. Another example of negative feedback occurs when your body's temperature begins to rise and a negative feedback response works to counteract and stop the rise in temperature. Sweating is a good example of negative feedback. Source: Biology4kids.com

4. Negative Feedback Examples
A good example of a negative feedback mechanism is a home thermostat (heating and a/c system). The thermostat contains the receptor (thermometer) and control center. If the a/c system is set at 75 degrees Fahrenheit, the air (effector) is turned on if the temperature rises above 75 degrees Fahrenheit. After the a/c cools the house to 75 degrees Fahrenheit, it shuts off effectively maintaining the ideal temperature.
“The control of blood sugar (glucose) by insulin is another good example of a negative feedback mechanism. When blood sugar rises, receptors in the body sense a change . In turn, the control center (pancreas) secretes insulin into the blood effectively lowering blood sugar levels. Once blood sugar levels reach homeostasis, the pancreas stops releasing insulin.”

5. Biological Negative Feedback
Human body temperature - The hypothalamus of a human responds to temperature fluctuations and responds accordingly. If the temperature drops, the body shivers to bring up the temperature and if it is too warm, the body will sweat to cool down due to evaporation.
Human blood pressure - When blood pressure increases, signals are sent to the brain from the blood vessels. Signals are sent to the heart from the brain and heart rate slows down, thus helping blood pressure to return to normal.
When a human is hungry, metabolism slows down to conserve energy and allow the human to continue living with less food.
Regulation of blood sugar in humans - When blood sugar rises, insulin sends a signal to the liver, muscles and other cells to store the excess glucose. Some is stored as body fat and other is stored as glycogen in the liver and muscles.
Production of human red blood cells (erythropoiesis) - A decrease in oxygen is detected by the kidneys and they secrete erythropoietin. This hormone stimulates the production of red blood cells.

6. More Examples of Negative Feedback
The ballcock in a toilet rises as the water rises, and then it closes a valve that turns off the water.
A spring can be compressed but will return to its original shape when pressure on it is released.
Population of predators and prey - If the numbers of prey decreases, then some predators will starve, and their numbers will decrease.
Being reprimanded for coming to work late.
A teacher marking a test to show the wrong answers.
Source: examples.yourdictionary.com

7. Examples
Ballcock in a toilet

8. Positive feedback
Positive feedback is the opposite of negative feedback in that encourages a physiological process or amplifies the action of a system. Positive feedback is a cyclic process that can continue to amplify your body's response to a stimulus until a negative feedback response takes over. An example of positive feedback also can happen in your stomach. Your stomach normally secretes a compound called pepsinogen that is an inactive enzyme. As your body converts pepsinogen to the enzyme pepsin, it triggers a process that helps convert other pepsinogen molecules to pepsin. This cascade effect occurs and soon your stomach has enough pepsin molecules to digest proteins. Source: Biology4kids.com

9. Positive Feedback Examples
“A good example of a positive feedback system is child birth. During labor, a hormone called oxytocin is released that intensifies and speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle goes on until the baby is born. The birth ends the release of oxytocin and ends the positive feedback mechanism.
Another good example of a positive feedback mechanism is blood clotting. Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed.”

10. Negative vs. Positive Feedback
“Just remember that positive feedback mechanisms enhance the original stimulus and negative feedback mechanisms inhibit it.”
Source: anatomyandphysiologyi.com

11. Homeostatic Control
To maintain homeostasis, communication within the body is essential. The image below is an example of how a homeostatic control system works. Here is a brief explanation:
Stimulus– produces a change to a variable (the factor being regulated).
Receptor– detects the change. The receptor monitors the environment and responds to change (stimuli).
Input– information travels along the (afferent) pathway to the control center. The control center determines the appropriate response and course of action.
Output– information sent from the control center travels down the (efferent) pathway to the effector.
Response– a response from the effector balances out the original stimulus to maintain homeostasis.
Source: anatomyandphysiologyi.com

13. Body temperature
A good example of system regulation of your body can be found in the regulation of body temperatures. You are a homoeothermic organism, which means you regulate your own body temperature. Other species like reptiles are not homoeothermic. Anyway, if your body gets too cold, a series of actions are taken to warm your body. Sensors throughout your nervous system can recognize when the temperature drops and might trigger your muscular system to start shivering. The constant contractions of your muscles allow heat to be generated. Your nervous and endocrine systems may also contract the blood vessels of your circulatory system to keep blood in the core of your body and not the extremities (like fingers). Source: Biology4kids.com

14. Body Temperature

15. Source: glogster.com

16. Source: 4.bp.blogspot.com

17. Source: classconnection.s3.amazonaws.com

18. Source: www.pinterest.com

19. Source: smartsite.ucdavis.edu