1. It does not have to do with food… But, you have some in your body Partnership for Environmental Education and Rural Health peer.tamu.edu

2. What is Feedback? Feedback is a response within a system (molecule, cell, organism, or population) that influences the continued activity or productivity of that system.

3. Negative Feedback Negative feedback is a regulatory mechanism in which a 'stimulus' causes an opposite 'output' in order to maintain an ideal level of whatever is being regulated. Negative feedback is a regulatory mechanism in which a 'stimulus' causes an opposite 'output' in order to maintain an ideal level of whatever is being regulated. A thermostat is an example of a negative feedback system. A thermostat is an example of a negative feedback system.

4. A thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. Room temp is below the setpoint Room temp is above the setpoint Room temp increases Room temp decreases Set point is reached Set point is reached

5. Negative Feedback in Biology Negative feedback also regulates many systems in organisms. Negative feedback also regulates many systems in organisms. The endocrine system is one example. The endocrine system is one example. This diagram shows a negative feedback loop for stress hormones. This diagram shows a negative feedback loop for stress hormones. Areas of negative feedback are indicated with a minus sign, (-). Areas of negative feedback are indicated with a minus sign, (-).

6. Endocrine System The endocrine system is The endocrine system is composed of glands that composed of glands that produces chemical produces chemical messengers called hormones. messengers called hormones. Hormones are produced in Hormones are produced in one part of the body and travel to target organs through the bloodstream. one part of the body and travel to target organs through the bloodstream.

7. Endocrine system Glands of the endocrine system include: Glands of the endocrine system include: Pituitary gland Pituitary gland Thyroid Gland Thyroid Gland Parathyroid glands Parathyroid glands Thymus Thymus Adrenal glands Adrenal glands Pancreas Pancreas Ovary and Testis Ovary and Testis

8. nervous System The brain continuously sends signals to the endocrine glands to secrete and release hormones and the glands, in turn, send feedback to the nervous system. The hypothalamus in the brain is the master switch that sends signals to the pituitary gland which can release up to eight hormones into the bloodstream. The hormone travels to its target organ and usually results in the release of another hormone into the bloodstream.

9. homeostasis The hypothalamus then detects the rising hormone levels from the target organ and decreases the release of hormones from the pituitary which results in a decrease in hormone release from the target organ. The hypothalamus then detects the rising hormone levels from the target organ and decreases the release of hormones from the pituitary which results in a decrease in hormone release from the target organ. The process of maintaining normal body function through negative feedback mechanisms is called homeostasis. The process of maintaining normal body function through negative feedback mechanisms is called homeostasis.

10. Homeostasis conditions within the body must remain within a narrow range – like your body temperature Homeostasis involves keeping the internal environment within set ranges

11. Glucose and Insulin Glucose intake occurs during digestion of food that is needed for energy expenditure to perform routine physical activities. Glucose intake occurs during digestion of food that is needed for energy expenditure to perform routine physical activities. The pancreas is the key organ that regulates the glucose levels in body by secreting two hormones, insulin and glucagon. The pancreas is the key organ that regulates the glucose levels in body by secreting two hormones, insulin and glucagon. The liver also helps to store the excess glucose in form of glycogen to be utilized later. The liver also helps to store the excess glucose in form of glycogen to be utilized later. Pancreas Liver

12. Glucose and Insulin Negative Feedback Loop Increases Glucose Levels Boy eating cake Stimulates β cells of pancreas to secrete insulin Insulin stimulates the cells to take up glucose from the blood. Lowers Blood Glucose levels CYCLE 1 (-)

13. Low Blood Glucose Levels Stimulated Alpha Cells in Pancreas Glucagon is released Glucagon stimulates liver cells to release glucose into the blood High blood glucose levels and Cycle 1 continues CYCLE 2 (-)

14. Glucose and Insulin Negative Feedback Loop Two primary Hormones Two primary Hormones The opposite actions of these two hormones, insulin and glucagon, helps to maintain normal blood sugar levels in the body hence maintain homeostasis of the body. The opposite actions of these two hormones, insulin and glucagon, helps to maintain normal blood sugar levels in the body hence maintain homeostasis of the body. InsulinGlucagon Lowers Blood Glucose Levels Raises Blood Glucose Levels

15. Kidneys and Water Regulation The kidneys play a key role in maintaining The kidneys play a key role in maintaining water regulation. water regulation. Renal Cortex Renal Cortex Renal Medulla Renal Medulla

16. Kidney and Water Regulation The nephron is the most important functional part of the kidney. It filters nutrients like salts and amino acids in the Bowman’s capsule into ascending loop and filters the urine.

17. Kidney and Water Regulation Anti-Diuretic Hormone, ADH (also called vasopressin), is secreted by the pituitary gland and acts on the nephron to conserve water and regulate the tonicity of body fluids. Anti- Diuretic Hormone ADH acts on Nephron to reabsorb water and decrease blood osmolality (saltiness)

18. ADH regulated water conservation in kidneys Excess water in the blood Stimulates osmoreceptors in hypothalamus to send signals to the pituitary gland Pituitary glands secretes low levels of ADH Less ADH makes the tubules less permeable and less water is reabsorbed back into the bloodstream (urine is dilute). Less water in the blood ADH makes the tubules more permeable and more water is reabsorbed back into the bloodstream (urine is concentrated). Stimulates osmoreceptors in hypothalamus to send signals to the pituitary gland Pituitary glands secretes high levels of ADH

19. Temperature regulation of Body Animals that are capable of maintaining their bogy temperature within a given range are called homeotherms. Temperature is regulated by negative feedback control. Thermoreceptors located in hypothalamus detect temperature fluctuations in the body.

20. Temperature Regulation of the Body Increased temperature causes vasodilatation (blood vessels near the surface of the skin dilate). The large surface area allows heat to be lost from the blood and lowers the body temperature. Sweat also helps lower the temperature.

21. Decreased temperature causes vasoconstriction (blood vessels constrict) and minimal heat loss occurs which helps maintain body temperature. Decreased temperature causes vasoconstriction (blood vessels constrict) and minimal heat loss occurs which helps maintain body temperature. Hair on the body provides insulation and helps maintain body temperature. Hair on the body provides insulation and helps maintain body temperature. Shivering causes the muscles to contract, releasing heat Shivering causes the muscles to contract, releasing heat

22. Positive Feedback A positive feedback loop occurs when the output of a system acts to enhance the changes to the input of the system. One example of a biological positive feedback loop is the onset of contractions in childbirth. When a contraction occurs, the hormone oxytocin is released into the body, which stimulates further contractions.oxytocin This results in contractions increasing in amplitude and frequency.

23. Positive Feedback Another example is blood clotting.blood clotting The loop is initiated when injured tissue releases signal chemicals that activate platelets in the blood. An activated platelet releases chemicals to activate more platelets, causing a rapid cascade and the formation of a blood clot. Lactation involves positive feedback so that the more the baby suckles, the more milk is produced. Lactation

24. Positive Feedback In most cases, once the purpose of the feedback loop is completed, counter-signals are released that suppress or break the loop. Childbirth contractions stop when the baby is out of the mother's body. Chemicals break down the blood clot. Lactation stops when the baby no longer nurses.