GCSE Physical Education

Aerobic and Anaerobic Respirationand the Respiratory System

Topic Objectives (what you will learn) Content (you should understand this)

Aerobic respiration

To be aware of the components that make up the respiratory system.To consider what is meant by aerobic respiration.To consider the process of gaseous exchange.To look at and understand the action of breathing.

Aerobic respiration in the presence of oxygen, summarised as:glucose + oxygen = energy + carbon dioxide + water

Anaerobic respiration

To consider what is meant by anaerobic respiration and the types of exercise that require it.To consider what takes place during the recovery period.To consider the function and role of the blood in this process.

Anaerobic respiration in the absence of oxygen, summarised as:glucose = energy + lactic acid.Oxygen debt as the result of muscles respiring anaerobically during vigorous exercise and producing a mild poison called lactic acid.The recovery process from vigorous exercise.

The respiratory system

The respiratory system

The nasal passages and lungsAir is drawn into the body via the nose or mouth. There are advantages to breathing through your nose:

Air then travels through the larynx, trachea (windpipe), bronchi (one bronchus to each lung) and bronchioles to the alveoli, where oxygen passes into the bloodstream.

the air is warmed so that it is closer to body temperature

tiny hairs and mucus in the nose filter the air, preventing larger dust and pollen particles reaching the alveoli

mucus moistens the air, making it easier for the alveoli to absorb.

When you breathe in:

intercostal muscles between the ribs contract, pulling the chest walls up and out

the diaphragm muscle below the lungs contracts and flattens, increasing the size of the chest

the lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth.

Mechanisms of breathing – inspiration

Diaphragm contracts and moves down

Intercostal muscles pull ribs

up and out

Mechanisms of breathing – inspiration

Mechanisms of breathing – expiration

When you breathe out:

Intercostal muscles between the ribs relax so that the chest walls move in and down.

The diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest.

The lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth.

Diaphragm relaxes and bulges up

Ribs move in and down

Mechanisms of breathing – expiration

Measuring breathing

Tidal volume is the amount you breathe in and out in one normal breath.

Residual volume is the amount of air left in your lungs after you have breathed out as hard as you can.

Minute volume is the volume of air you breathe in one minute.

Respiratory rate is how many breaths you take per minute.

Vital capacity is the maximum volume of air you can breathe out after breathing in as much as you can.

You do not need to remember this

Measuring breathingYou do not need to remember this

Measuring breathingYou do not need to remember this

Calculating minute volume

Question

If you breathe 14 times in one minute (respiratory rate) and you breathe 0.5 litres in each breath, what is your minute volume?

Answer:Minute volume = 14 × 0.5 litres

= 7.0 litres

Remember:

You can calculate a person’s minute volume by multiplying the volume of air they breathe in one breath, by their respiratory (breathing) rate.

Minute volume is the volume of air you breathe in one minute.

You do not need to remember this

Gas exchange at the alveoliThe alveoli are bunches of tiny air sacks inside the lungs.

Each individual sack is called an alveolus.

When you breathe in, they fill with air.

The alveoli are covered in tiny capillaries (blood vessels).

Gases can pass through the thin walls of each alveolus and capillary, and into the blood stream.

Gases can also pass from the blood stream, into the alveolus.

Gas exchange at the alveoli

Composition of inhaled and exhaled air

GasAmount in inhaled air

Amount in exhaled air

Oxygen

Carbon dioxide

Nitrogen

Water vapour

17%

3%

79%

Large amount

21%

Very small amount

79%

Small amount

Why does mouth-to-mouth resuscitation work?

What are the main differences between inhaled and exhaled air?

Breathing during exerciseDuring exercise the muscle cells use up more oxygen and produce increased amounts of carbon dioxide.

Your lungs and heart have to work harder to supply the extra oxygen and remove the carbon dioxide.

Your breathing rate increases and you breathe more deeply.

Heart rate also increases in order to transport the oxygenated blood to the muscles.

Breathing during exercise

Muscle cell respiration increases – more oxygen is used up and levels of CO2 rise.

The brain detects increasing levels of CO2 – a signal is sent to the lungs to increase breathing.

Breathing rate and the volume of air in each breath increase. This means that more gaseous exchange takes place.

The brain also tells the heart to beat faster so that more blood is pumped

to the lungs for gaseous exchange.

More oxygenated blood gets to the muscles and more CO2 is removed.

Breathing changes during exercise

During rest During exercise

Respiratory rate 14 breaths/ minute 32 breaths/ minute

Volume per breath

0.4 litres 2.4 litres

Minute volume ? ?

Look at these statistics for a 16 year-old athlete:

Calculate the athlete’s minute volumes during rest and exercise.

Rest minute volume = 5.6 litresExercise minute volume = 76.8 litres

You do not need to remember this

Respiration

Glucose from food is used to fuel exercise.

Respiration is the process that takes place in living cells which releases energy from food molecules.

Waste products, including carbon dioxide, are produced as a result of the chemical reactions. These must be removed and excreted.

glucoseoxygen

energy

respirationOxygen is required to ‘break down’ the glucose to produce energy. This energy is used to make muscles contract.

Aerobic respiration

Aerobic exercise can be maintained for long periods without the performer getting breathless or suffering muscle cramps. Moderate activities like walking, jogging, cycling and swimming use aerobic respiration.

There are two different types of respiration.

When you exercise at a steady, comfortable rate, the cardiovascular system is able to supply the muscles with all the oxygen they need.

Under these conditions, aerobic respiration takes place.

glucose + oxygen energycarbon dioxide

+ + water

Aerobic respiration

Anaerobic respirationWhen you exercise at a high intensity, the cardiovascular system cannot supply enough oxygen to the muscles.

Under these conditions, anaerobic respiration takes place.

With no oxygen available, glucose is burned to produce energy and lactic acid.

Lactic acid is a mild poison. As it builds up, it causes muscle pain and eventually cramp.

Short, intense activities like sprinting, weightlifting, jumping and throwing use anaerobic respiration.

glucose energy + lactic acid

Oxygen debtAfter anaerobic activity, oxygen is needed to neutralize the lactic acid. This is called an oxygen debt. It is repaid after exercise.

The oxygen reacts with the lactic acid to form CO2 and water.

Rapid and deep breathing is needed for a short period after high intensity exercise in order to repay the debt.

This also helps to remove the carbon dioxide which accumulates in the blood during intense exercise.

Anaerobic exercise

The effects of exercise on lung structures

The respiratory muscles (the diaphragm and intercostals) get stronger, so they can make the chest cavity larger.

This larger chest cavity means more air can be inspired, therefore increasing your vital capacity.

More capillaries form around the alveoli, so more gaseous exchange can take place.

In the long-term, regular exercise strengthens the respiratory system.

Gas exchange can now take place more quickly meaning exercise can be maintained

at a higher intensity for longer.

Exam-style questions1. Describe the passage of oxygen from the nasal passages

to the bloodstream.

2. David goes jogging once a week for 45 minutes.

David tries to increase his pace. He finds that he is forced to stop running and breathe hard for several minutes.

a) List two differences between the air that David inhales and the air that he exhales while jogging.

b) What two substances are used by David’s body cells to produce energy? What are the products of this reaction?

c) Explain why David had to stop.

d) How did breathing hard help him to recover?

Can you remember all these keywords?

Larynx

Trachea

Bronchus / Bronchi

Bronchioles

Alveoli

Diaphragm

Intercostal muscles

Oxygen uptake

Respiratory rate

Aerobic respiration

Anaerobic respiration

Oxygen debt

Lactic acid