It does not have to do with food…But, you have some in your body

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What is Feedback?What is Feedback?

Feedback is the Feedback is the process in which part process in which part of the output of a of the output of a system is returned to system is returned to its input in order to its input in order to regulate its further regulate its further output.output.

Negative FeedbackNegative Feedback

NegativeNegative feedback occurs when the feedback occurs when the output of a system acts to output of a system acts to opposeoppose changes to the input of the system.changes to the input of the system.

A thermostat is an example of a A thermostat is an example of a negative feedback system.negative feedback system.

A thermostat is a device for regulating the temperature of a A thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a system so that the system's temperature is maintained near a desired desired setpointsetpoint temperature. 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

Negative Feedback in Negative Feedback in BiologyBiology

Negative feedback also Negative feedback also regulates many systems regulates many systems in organisms.in organisms.

The endocrine system is The endocrine system is one example.one example.

This diagram shows a This diagram shows a negative feedback loop negative feedback loop for stress hormones.for stress hormones.

Areas of negative Areas of negative feedback are indicated feedback are indicated with a minus sign, (-).with a minus sign, (-).

Endocrine SystemEndocrine System

The endocrine system isThe 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 one part of the body and

travel to target organs travel to target organs through the bloodstream. through the bloodstream.

Endocrine systemEndocrine system

Glands of the endocrine Glands of the endocrine system include:system include:

Pituitary glandPituitary gland Thyroid GlandThyroid Gland Parathyroid glandsParathyroid glands ThymusThymus Adrenal glandsAdrenal glands PancreasPancreas Ovary and TestisOvary and Testis

Endocrine SystemEndocrine 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.

Endocrine SystemEndocrine System

The hypothalamus then detects the rising hormone The hypothalamus then detects the rising hormone levels from the target organ and decreases the levels from the target organ and decreases the release of hormones from the pituitary which results release of hormones from the pituitary which results in a decrease in hormone release from the target in a decrease in hormone release from the target organ. organ.

The process of maintaining normal body function The process of maintaining normal body function through negative feedback mechanisms is called through negative feedback mechanisms is called homeostasishomeostasis..

Glucose and InsulinGlucose and Insulin Glucose intake occurs during Glucose intake occurs during

digestion of food that is needed digestion of food that is needed for energy expenditure to perform for energy expenditure to perform routine physical activities.routine physical activities.

The pancreas is the key organ that The pancreas is the key organ that regulates the glucose levels in regulates the glucose levels in body by secreting two hormones, body by secreting two hormones, insulin and glucagon.insulin and glucagon.

The liver also helps to store the The liver also helps to store the excess glucose in form of glycogen excess glucose in form of glycogen to be utilized later.to be utilized later.

Pancreas

Liver

Glucose and Insulin Negative Feedback Glucose and Insulin Negative Feedback LoopLoop

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(-)

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

(-)

Glucose and Insulin Negative Feedback Glucose and Insulin Negative Feedback LoopLoop

Two primary HormonesTwo primary Hormones

The opposite actions of these two hormones, insulin and The opposite actions of these two hormones, insulin and

glucagon, helps to maintain normal blood sugar levels in glucagon, helps to maintain normal blood sugar levels in the body hence maintain homeostasis of the body.the body hence maintain homeostasis of the body.

Insulin Glucagon

Lowers Blood Glucose Levels

Raises Blood Glucose Levels

Take a Break and Chat With Your Take a Break and Chat With Your Neighbor!Neighbor!

Turn to the person behind or in front of Turn to the person behind or in front of you and discuss the following topics:you and discuss the following topics:

What is a What is a feedbackfeedback and an example of a and an example of a negative AND positive system?negative AND positive system?

What is the What is the endocrine system endocrine system and why is it and why is it important?important?

Define Define homeostasis homeostasis and how normal body and how normal body function is maintained with feedback function is maintained with feedback mechanisms.mechanisms.

Kidneys and Water RegulationKidneys and Water Regulation

The kidneys play a key role in maintainingThe kidneys play a key role in maintaining water regulation.water regulation. Renal CortexRenal Cortex

Renal Medulla Renal Medulla

Kidney and Water RegulationKidney 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.

Kidney and Water RegulationKidney 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- DiureticHormone

ADH acts on Nephron to reabsorb water and decrease blood osmolality (saltiness)

ADH regulated water conservation in ADH regulated water conservation in kidneyskidneys

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

ADH regulated water conservation in ADH regulated water conservation in kidneyskidneys

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.

Temperature regulation of BodyTemperature 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.

Temperature Regulation of the BodyTemperature 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.

Positive FeedbackPositive 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.

This results in contractions increasing in amplitude and frequency.

Positive FeedbackPositive 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.

Positive FeedbackPositive 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.

Take a Break and Chat With Your Take a Break and Chat With Your Neighbor!Neighbor!

Turn to the person behind or in front of you Turn to the person behind or in front of you and discuss the following topics:and discuss the following topics:

What are the roles of the What are the roles of the kidneyskidneys in the body? in the body?

How do the How do the kidneyskidneys compare or contrast to compare or contrast to the the feedbackfeedback systems in the systems in the endocrineendocrine system?system?

How does the body How does the body regulate temperatureregulate temperature??

Define and give examples of a Define and give examples of a positive positive feedback feedback system in the body. system in the body.