Feedback Loops and Homeostasis

Homeostasis & Feedback

By Ralf Chono-Schaa

​Make notes as you work through this lesson

Homeostasis and Feedback

Learning Objectives

• I can define homeostasis and list examples

• I can describe the a negative feedback loop and list examples

• I can describe the process of temperature regulation

Homeostasis and Feedback

Take Notes

• While working through this interactive lesson, take notes of the various information on homeostasis and feedback

Multiple Select

A) Why do runners drink "sports" drinks rather than water? Select the most applicable answers.

• The drinks provide needed energy in the form of sugar

• The drinks motivate the runner

• Sports drinks can replenish body fluids

• The colour in the drinks have a positive effect

Open Ended

Write three things your body needs to keep stable/constant.

Open Ended

If you can, discuss with your neighbour:

Rank your three 'things' from most important to least important and why:

Homeostasis & Feedback

The following slides show various scenarios

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For each scenario answer the questions

Multiple Select

Drinking Cold Water

What are Two Things that Change in the Body:

• Solute concentration in cells increases

• Amount of water in blood increased

• Body temperature decreased

• Body temperature remains steady

Homeostasis & Feedback

Drinking Cold Water

• Amount of water in blood increased

• Body temperature decreased

Multiple Select

Free Diving

Select all things that are changing in your body

• Decreased Oxygen levels in blood

• Decrease in temperature

• Increased Carbon Dioxide levels in blood

• Increase in waste levels in blood

Homeostasis & Feedback

Free Diving

• Decreased Oxygen levels in blood

• Increased Carbon Dioxide levels in blood

• Increase in waste levels in blood

• IGNORE Temperature (you don't know how hot the water is) ​

Multiple Select

Standing on top of Mount Everest

Select the things that are changing in your body

• Decreased oxygen levels

• Decreased temperature

• Increased loss of heat

• Increased levels of cell osmosis

Homeostasis & Feedback

​Standing on top of Mount Everest

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• Decreased oxygen levels

• Decreased temperature

• Increased loss of heat

Open Ended

Sunbathing

Write two things that are changing in your body

​Some text here about the topic of discussion.

Sunbathing

• Increased blood temperature

• Decreased heat loss

• Reduced water levels

• Resalt levelsduced

Homeostasis is the maintenance of a constant internal environment

(i.e. keeping the conditions inside your body the same)

Homeostasis

Definition

Some of the major internal conditions that need to be maintained at optimal levels by homeostasis include:​

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• Blood glucose levels

• Blood water levels

• Body temperature

• Blood oxygen levels

Homeostasis & Feedback

Homeostasis

• Our body tries to stay at a constant temperature (37.5°) as this is the ideal temperature for chemical reactions in our body cells

• To keep the temperature the same it must balance the heat lost and heat gained​

Homeostasis & Feedback

Homeostasis

Fill in the Blank

Provide two things how your body can gain or lose heat or help control temperature

• Our bodies use behavioural and physiological methods to control our temperature

• Behavioural = change clothes, cold drink, seek a cool place, reducing/increasing activity

• Physiological = sweating, goose bumps, shivering

Homeostasis & Feedback

Homeostasis

Fill in the Blank

Which is NOT under conscious control? Physiological or behavioural methods?

A receptor* that detects a change away from the normal

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​(*chemical structures that receive and transduce signals in your body)

Sensor

Processing centre to decide what to do, or coordinate the response

​​Computer Chip

An effector that can be activated to bring about a change

​​Light Bulb

​All automatic control systems, including the ones in your body have 3 parts, and messages are exchanged between them:

1. Receptor ➔ 2. Processing Centre ➔ 3. Effector

Multiple Select

Identify the correct control systems:

• Transducer

• Receptor

• Regulator

• Processing centre

• Effector

​Homeostasis & Negative Feedback

From the diagram, you can see that maintaining homeostasis involves feedback, which is data that feeds back to control a response.

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High body temperature may stimulate the temperature regulatory centre of the brain to activate the sweat glands to bring the body temperature down. When body temperature reaches normal range, it acts as negative feedback to stop the process. ​

Open Ended

Briefly explain in 3 dot points how your body maintains a steady 37 °C temperature using the concept of negative feedback.

Negative feedback occurs when a change in a regulated variable triggers a response which reverses the initial change and brings the regulated variable back to the set point.​

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​In a negative feedback loop, feedback serves to reduce an excessive response & keep a variable within the normal range

(e.g. temperature or blood glucose level)

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Homeostasis & Feedback

Negative Feedback

Multiple Choice

What is a feedback mechanism?

• A physiological regulation system in a living body that works to maintain the body in an excited internal state

• A physiological regulation system in a living body that works to return the body to its abnormal internal state

• A physiological regulation system in a living body that works to prevent the body from returning to its normal internal state

• A physiological regulation system in a living body that works to return the body to its normal internal state

7 Components of a Feedback Loop

1. Stimulus - the change in the internal environment

2. Receptor - detects the change

3. Modulator (coordinator) - control centre that processes information from the receptor & sends information to the effector

4. Message - the information that is sent from the modulator to the effector

5. Effector - the part of the body that carries out the response

6. Response - the process that occurs in the effector

7. Feedback - the change in internal conditions

Homeostasis & Feedback

Fill in the Blank

Look at the image, which two steps are missing. Write below in the correct order.

• Most homeostatic control mechanisms display negative feedback.

• Negative feedback is when the response is opposite to the stimulus and returns the body to its set point.​

Open Ended

Research POSITIVE feedback loops on the internet. Briefly explain what a positive feedback loop is and provide one example.

Homeostasis Interactive

The following slide provides a link to a homeostasis interactive.

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​Click at the top on "Open in new tab".

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​Try to adjust the various body systems to maintain homeostasis

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Don't spend more than 5 minutes on this​

Biology

Homeostasis & Feedback

Home

Open in new tab

Copy link

​https://pbslm-contrib.s3.amazonaws.com/WGBH/conv16/conv16-int-bcc/index.html

Open Ended

Reflection:

What was the most significant insight that you got from the interactive?

Multiple Choice

What is NOT an example of Homeostasis?

• While exercising, Julia's heart rate and breathing increase to balance the increased oxygen use by her muscle cells.

• After plunging into icy-cold water, Gary's core body temperature rapidly drops.

• On a hot day, to prevent dehydration, Martin’s kidneys remove very little water from his blood.

• After eating a candy bar, April's pancreas secretes insulin, which removes the excess blood sugar.

Multiple Choice

What is another word that can be used to describe "homeostasis"?

• STABLE

• EQUAL

• COMPLETE

• CORRECT

Multiple Choice

Which of the following is NOT regulated by homeostasis?

• body temperature

• blood sugar

• body movements

• blood pH

Fill in the Blank

____________ is the process of keeping a constant amount of water and salts in the blood

Multiple Choice

This graph shows an example of...

• Blood sugar regulation

• Homeostasis

• Negative feedback

• Positive feedback

Multiple Choice

The "cause" for something to happen is the

• response

• effect

• stimulus

• homeostasis

Fill in the Blank

The "effect" of a given stimulus is the...

Multiple Choice

What type of feedback loop is shown?

• Positive

• Negative

Multiple Choice

Negative Feedback Loops:

• amplify processes

• prevent small changes from getting larger

• are initiated during childbirth

• are found only in plants

Multiple Select

Positive feedback involves a response that reinforces the change detected (it functions to amplify the change)

What are two examples of a positive feedback loop?

• Childbirth

• Sweating

• Blood clotting

• Shivering

Read carefully, analyse the diagram and answer the questions. Finish at home.

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Start with the Worksheet