Presentation on theme: "Partnership for Environmental Education and Rural Health"— Presentation transcript:
1 Partnership for Environmental Education and Rural Health FEEDBACK MECHANISMSIt does not have to do with food…But, you have some in your bodyPartnership for Environmental Education and Rural Healthpeer.tamu.edu
2 What is Feedback?Feedback is the process in which part of the output of a system is returned to its input in order to regulate its further output.
3 Negative FeedbackNegative feedback occurs when the output of a system acts to oppose changes to the input of the system.A thermostat is an example of a negative feedback system.
4 Heater turns off Heater turns on AC turns off AC turns on Room temp increasesSet pointis reachedHeater turns onHeater turns offRoom temp is below the setpointRoom temp is above the setpointSet pointis reachedRoom temp decreasesAC turns offAC turns onA thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature.
5 Negative Feedback in Biology Negative feedback also regulates many systems in organisms.The endocrine system is one example.This diagram shows a negative feedback loop for stress hormones.Areas of negative feedback are indicated with a minus sign, (-).
6 Endocrine System The endocrine system is composed of glands that produces chemicalmessengers called hormones.Hormones are produced inone part of the body and travel to target organs through the bloodstream.
7 Endocrine system Glands of the endocrine system include: Pituitary glandThyroid GlandParathyroid glandsThymusAdrenal glandsPancreasOvary and Testis
8 Endocrine SystemThe 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 brainis the master switch thatsends signals to the pituitarygland 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 Endocrine SystemThe 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.
10 Glucose and InsulinPancreasGlucose 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 liver also helps to store the excess glucose in form of glycogen to be utilized later.Liver
11 Glucose and Insulin Negative Feedback Loop Boy eating cakeIncreases Glucose Levels(-)CYCLE 1Stimulates β cells of pancreas to secrete insulinLowers Blood Glucose levelsInsulin stimulates the cells to take up glucose from the blood.
12 CYCLE 2 Low Blood Glucose Levels Glucagon is released (-)Stimulated Alpha Cells in PancreasHigh blood glucose levels and Cycle 1 continuesGlucagon is releasedGlucagon stimulates liver cells to release glucose into the blood
13 Glucose and Insulin Negative Feedback Loop Two primary HormonesThe 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.InsulinGlucagonLowers Blood Glucose LevelsRaises Blood GlucoseLevels
14 Take a Break and Chat With Your Neighbor! Turn to the person behind or in front of you and discuss the following topics:What is a feedback and an example of a negative AND positive system?What is the endocrine system and why is it important?Define homeostasis and how normal body function is maintained with feedback mechanisms.
15 Kidneys and Water Regulation The kidneys play a key role in maintainingwater regulation.Renal CortexRenal 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-DiureticHormoneADH acts on Nephron to reabsorb water and decrease blood osmolality (saltiness)
18 ADH regulated water conservation in kidneys Excess water in the bloodLess water in the bloodStimulates osmoreceptors in hypothalamus to send signals to the pituitary glandStimulates osmoreceptors in hypothalamus to send signals to the pituitary glandPituitary glands secretes high levels of ADHPituitary glands secretes low levels of ADHLess ADH makes the tubules less permeable and less water is reabsorbed back into the bloodstream (urine is dilute).ADH makes the tubules more permeable and more water is reabsorbed back into the bloodstream (urine is concentrated).
19 ADH regulated water conservation in kidneys Osmoregulators send negative feedback to the hypothalamus about the concentration of water in the bloodstream.The hypothalamus then stimulates the pituitary glands to secrete high or low concentrations of anti-diuretic hormone.ADH then makes the tubules more or less permeable and hence, maintains water and electrolyte homeostasis.
20 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.
21 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.Sweating also helps lower the 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.
22 Positive FeedbackA 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.This results in contractions increasing in amplitude and frequency.
23 Positive Feedback Another example is 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.
24 Positive FeedbackIn 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.
25 Take a Break and Chat With Your Neighbor! Turn to the person behind or in front of you and discuss the following topics:What are the roles of the kidneys in the body?How do the kidneys compare or contrast to the feedback systems in the endocrine system?How does the body regulate temperature?Define and give examples of a positive feedback system in the body.