The Respiratory System
GCSE
Learning Outcomes
By the end of today’s lesson you should:
 Be aware of what respiration is and its
components
 Be aware of the process involved when
we inhale (breathe in) and exhale
(breathe out).
 Know the difference between aerobic and
anaerobic respiration
 Be familiar with the term “Gaseous
Exchange.”

What is Respiration?
Respiration is the process in which
glucose is converted into energy useable
for life processes.
 Respiration involves the important
component of breathing but be careful
not to confuse respiration as just solely
breathing.
 There are 2 types of respiration that our
bodies use for different activities...

Aerobic Respiration
Anaerobic Respiration
What is the difference between
Aerobic and Anaerobic Respiration?
Q. Aerobic respiration occurs in the
presence of...
 A. Oxygen
 Example of an Aerobic activity – Marathon
Running
 Q. Anaerobic respiration occurs in the
ABSENCE of...
 A. Oxygen
 Example of Anaerobic activity – 100m Sprint

Aerobic Respiration

Aerobic respiration occurs in the presence
of oxygen and is summarised by the
following equation:

Glucose + Oxygen  Energy + Carbon Dioxide +Water
This type of respiration is used when the
body continues an activity for a prolonged
period of time.
 The energy that is needed to allow this
prolonged activity is produced using oxygen.

Aerobic Respiration Cont
In order for the aerobic system to
function effectively, there has to be a
constant supply of oxygen to the body
and the working muscles.
 For any activity that takes place over a
long period of time (e.g. Marathon) it is
important to have this constant supply of
oxygen to the body otherwise the body
would be unable to carry out the event.

Anaerobic Respiration

On the other hand, anaerobic respiration
is the process where energy is made in
the absence of oxygen.

The equation for anaerobic respiration is:

Glucose  Energy + Lactic Acid
Anaerobic Respiration Cont.




This type of respiration occurs when the
body works without sufficient oxygen being
delivered to the muscles.
Without the presence of oxygen, a waste
product called lactic acid is produced in the
muscles.
High lactic acid concentrations cause
muscles to feel painful and can lead to cramp.
As oxygen is not being used to generate
energy in anaerobic respiration, it can only
be used for short bursts e.g. 100m sprint
Aerobic or Anaerobic?
Aerobic or Anaerobic?
Aerobic or Anaerobic?
Aerobic or Anaerobic?
Aerobic or Anaerobic?
Aerobic or Anaerobic?
Oxygen Debt



When our bodies respire anaerobically
during vigorous exercise, supplies of oxygen
are reduced to working muscles.
As there is an absence of oxygen, the body
can only respire anaerobically for a
maximum of 60 seconds.
During an anaerobic event such as the 100m
sprint or a 50m freestyle event in swimming,
our bodies will effectively ‘borrow’ oxygen
and it will need to ‘paid back’ in order to
break down the waste products produced
(lactic acid).
Oxygen Debt
For example, Usain Bolt runs the 100m
race in under 10 seconds and after the
race finishes, he must continue to breathe
deeply and heavily in order to replenish
the oxygen or pay the oxygen debt.
 One of the main reasons for completing a
cool down after vigorous exercise is to
enable the oxygen debt to be repaid and
will allow any lactic acid to disperse which
will avoid further discomfort.

The Recovery Period
Following intense exercise we have to take in extra oxygen
which will help convert the lactic acid into simple waste
products that have to be removed from the body.
 Expiration of breath – removes the carbon dioxide and other
waste products from our lungs.
 Perspiration – is a form of temperature control and also
removes excess water such as sweat at the same time that it
is letting heat escape through evaporation from the skin.
Although this heat is not really a waste product it must be
released to prevent our bodies from overheating.
 Excretion through urine and faeces – removes excess water
and the other waste products from the lactic acid.

Breathing
This is a diagram of all the components involved in the breathing process
Inhalation (breathing in)


During inhalation:
The chest cavity changes shape and size.

The intercostal muscles contract which causes the rib cage to
expand and pushes out the sternum (chest/breastbone)

The diaphragm will contract and will change shape from a concave
or dome shape to a flattened shape.

The pressure inside the chest cavity will be reduced and therefore
allows air to be sucked into the lungs.

The air we breathe in is high in oxygen and nitrogen but low in
carbon dioxide.
Diagram of Inhalation
Exhalation (breathing out)

During exhalation:
The process is virtually reversed

The chest cavity changes in shape and size

The intercostal muscles relax, allowing the rib cage to drop
downwards and inwards.

The diapgrahm relaxes and regains its concave or domed shape and
this decreases the volume of the chest.

The pressure inside the chest will subsequently increase and force
air out. The air exhaled is high in nitrogen and carbon dioxide.

Diagram of Exhalation
Gaseous Exchange
Gaseous exchange is the process where
carbon dioxide is exchanged in the lungs
for oxygen by diffusion.
 The carbon dioxide produced as a waste
product of respiration must be exhaled
from the body and more oxygen is
needed through inhalation.
 Gaseous exchange takes place in the
alveoli in the lungs.

Gaseous Exchange Cont.
The diagram shows gaseous exchange occurring at the alveoli in
the lungs. The oxygen is taken into the blood and carried to the
heart to be pumped around the body and the carbon dioxide is
exhaled as a waste product of respiration.
Test
True or False?
Anaerobic exercise involves using oxygen
to produce energy.
 A triathlon competitor will use aerobic
respiration.
 Carbon dioxide is a waste product which
causes discomfort and pain in the
muscles.
 Anaerobic respiration will be used in
activities which can last up to 1 minute.

Questions???
What is the Oxygen Debt?
 Give 3 examples of aerobic activities
 Give 3 examples of anaerobic activities
 Give 2 example of a sport that will use
both aerobic and anaerobic respiration.
 What are the 2 main muscles/group of
muscles involved in breathing and
changing the shape and size of the chest.
