Exercise & Respiration

IGCSE Coordinated Science Topic 9.7 Animal Systems

Learning Objectives

• Understand why exercise changed breathing and pulse rate.

• Learn about the difference between aerobic and anaerobic respiration.

• Learn about oxygen debt. (Higher only)

Success Criteria

• I can find and measure my own pulse rate.

• I can explain the link between increased exercise and increased pulse/breathing rate.

• I can explain the link between anaerobic respiration and build up of lactic acid.

Starter

• Look at the pictures below and use them to help you detect your own pulse.

• Measure your pulse rate by counting the number of beats in one minute.

• Why might your pulse rate not be at the normal rate right now?

Starter

• Think about an average weekday and all of the things you might do during the course of the day.

• List what activities can raise or lower your pulse rate…

Exercising and Feeling Tired

• Let’s look back at the equation for aerobic respiration…

glucose + oxygen carbon dioxide + water

• When we exercise, our cells work harder and require more energy to be released. (respiration)

• Therefore, the cells need more glucose and oxygen.• Because of this, our breathing rate and pulse rate increase to

satisfy the demand.

When we exercise, we need more of these

two.

This means more of this is produced. It must be removed.

1. Cells need more glucose + oxygen

for respiration

2. Breathing rate + Pulse rate increase in order to deliver

glucose + oxygen to cells

3. High rate of respiration means lots of waste carbon

dioxide is produced

4. The high breathing and pulse rate means that the carbon dioxide can be

removed as quickly as possible.

Write out these steps under the heading

‘Exercise & Respiration’.

Recovery Rate

• Before a game of football, if you were to measure your pulse rate, the reading would be called the “resting rate”.

• After a game of football, the time taken for the pulse rate to return to the resting rate, is called the recovery rate.

puls

e ra

te

time

A B C D

What do you think each time period represents? Fill in your own blank

graph.

puls

e ra

te

time

A B C D

A:• Resting rate.• The normal number of beats per

minute when not doing exercise.

B:• The number of beats during exercise.• Lots of glucose/oxygen required by

cells, so heart pumps blood faster.

C:• The recovery rate.• This is the time taken for the pulse rate

to return back to normal.

D:• This is the resting rate again.• The pulse rate has returned back to

normal.

Anaerobic Respiration

• Anaerobic respiration is a type of respiration that can release energy without needing any oxygen.

• It occurs during hard exercise, when not enough oxygen can supplied for aerobic respiration to occur.

glucose lactic acid(that’s it!)

• The equation is very different to aerobic respiration and produces much less energy per glucose molecule.

• The lactic acid is poisonous and builds up in muscles after hard exercise.

Lactic Acid & Muscle Fatigue

• After intense exercise, lactic acid build-up causes muscles to stop working.

• This is called muscle fatigue.

• It is also known as cramp and can be very painful.

• You need to rest in order for the lactic acid to be broken down.

• Remember, lactic acid is only produced during hard exercise.

Practical: Fist Clenching!• Place your hand (palm-side up) on the desk.• One person in the group needs to have the

stopwatch. Ask them to count down ‘3, 2, 1, go!’ and then start the stopwatch to time 1 minute.

• When they say ‘go!’, start clenching your fist as fast as you can while your partner counts how many times you can open and close your hand in 1 minute. Do not stop! Keep going for the whole minute.

• Record how many times you managed to make a fist in the table on worksheet b3_c_02.

• Now repeat the experiment so that everyone in the group does the fist clenching.

• Repeat the experiment again, but this time the action should be raising your hand above your head and making fists.

• Record your results in the table worksheet b3_c_02.• If you have time each group member should do the

exercises again to see if they can improve on their previous scores.

Task

1. What type of respiration is used to release energy while you are asleep?

2. What type of respiration is used to release energy when you are sprinting?

3. What chemical is produced during anaerobic respiration?

4. Why do your muscles hurt after a hard game of football?

5. Explain the difference between aerobic and anaerobic respiration.

HIGHER

Oxygen Debt

• The lactic acid that has built up during anaerobic respiration needs to be broken down.

• Oxygen is required in the breakdown of lactic acid.• Heavy breathing after exercise provides the extra oxygen required

to break down lactic acid, and is known as the oxygen debt.• This is followed by panting to allow aerobic respiration to resume.

It gets broken down in the liver.

The blood carries the lactic acid there.

PLENARY

In your books, describe what will happen to your breathing rate and pulse rate as you

move towards your next destination in the college.

Explain the changes.