1. 3.1.1.3 The Respiratory system
Learning objectives
To be able to identify different lung volumes.
To understand the process of gaseous exchange.
To be able to define diffusion and partial pressure and its affect at the alveoli and body cells.
To understand the processes of external respiration and internal respiration.
To understand the roles of the receptors in the regulation of ventilation.
To explain the impact of a poor lifestyle on the respiratory system.

2. Understanding the respiratory system
This involves the LUNGS and works closely with the cardiovascular system.
Watch me
Watch me
What is the key function of the respiratory system?

3. Lung Volumes
The volume of air inspired or expired per breath is referred to as the tidal volume.
The volume of air inspired or expired per minute is the minute ventilation and can be calculated with the equation below:
Number of breathes x Tidal volume = Minute Ventilation (per min)
e.g. 12 breaths x 0.5 litres = 6 litres per minute.

4. Lung volumes can be shown on a spirometer trace.
The total lung capacity is calculated by adding the vital capacity of the lungs to the residual volume:
Lung volumes can be shown on a spirometer trace.

5. Change during exercise
Lung Volumes
Complete the table below from the information provided.
Lung Volume
Definition
Average value at rest
Change during exercise
Tidal Volume
Inspiratory Reserve Volume
Expiratory Reserve Volume
Residual Volume
Minute Ventilation
(VE = TV x f)

6. Inspiratory Reserve Volume
Tidal Volume
The volume of air inspired or expired per breath
Average – 0.5 litres
Change during exercise – (increase)
Inspiratory Reserve Volume
The volume able to be forcibly inspired during normal breathing
Average – 3.0 litres
Change during exercise (decrease)

7. Expiratory Reserve Volume
The volume able to forcibly expired, after a normal breathe
Average – 1.3 litres
Change during exercise – Small decrease
Residual Volume
The volume of air that remains in the lungs after forced maximum expiration
Average – 1.2 litres
No change

8. Minute ventilation (VE) = Tidal Volume (TV) X Breathing Rate (f)
Ventilation is the amount of air breathed in one minute.
Average – 6.0 litres
Changes during exercise = BIG increase
Minute ventilation calculation
Minute ventilation (VE) = Tidal Volume (TV) X Breathing Rate (f)
VE TV f
At rest – ,200 ml/min = ml X 12 At submax – 60,000 ml/min = 2400 ml X At max – ,000 ml/min = 2200 ml X 55

9. Minute Ventilation
Depth and rate of breathing increase in direct proportion to the intensity of the exercise.
Depth and rate of breathing increase because:
1. Working muscles demand oxygen
2. Need to remove carbon dioxide

10. Changes to minute ventilation during exercise
The more demanding the physical activity, the more breathing increases to meet the extra oxygen demand.
Maximal Exercise
Sub-Maximal Exercise
a = anticipatory rise b = sharp rise in minute ventilation c = slower increase d = steady state
e = rapid decline in minute ventilation f = slower recovery as body systems return to resting levels
Think. Pair. Share - Look at the 2 graphs, what are the differences?

11. Gas exchange
Watch me
During inspiration why does air enter the lungs?

12. Principles of Diffusion and Partial Pressure of gases
A gas will always move from an area of high pressure to an area of low pressure.
Alternatively….
A gas will always move from areas where there is more of it, to areas where there is less of it.

13. Diffusion in the lungs
Gases will always move from areas of high pressure to areas of low pressure.
Air
Lungs

14. Partial Pressure Atmospheric air is made up of 3 gases Nitrogen - 79 %
Oxygen %
Carbon Dioxide – 0.03 %
Partial Pressure explain movement of gases within the body.
Pressure is measured in … mmhg (millimetres of mercury)
Together the gases exert a pressure of 760mmHg

15. Partial Pressure
The individual pressure a gas exerts, when in a mixture of gases.
PO2 = 160 mmHg
PCO2 = 0.3mmHg

16. Partial Pressure of O2 and CO2 in the body
Partial pressure of oxygen in the alveoli is higher than the partial pressure of oxygen in the blood.
In alveoli
PO2 = 100mmHg
In blood
PO2 = 40mmHg
Why?
Oxygen has been removed by the working muscles.
So the concentration of oxygen in the blood is lower.
Therefore partial pressure is lower.

17. Diffusion Partial Pressure of O2 and CO2 in the body
Gas will always move from areas with a higher partial pressure to areas with a lower partial pressure until equilibrium is reached.
Diffusion
This is called:
In alveoli
PO2 = 100mmHg
In blood
PO2 = 40mmHg
Therefore oxygen will diffuse into the blood until the pressure is equal in the alveoli and the blood.

18. 60 mmHg Partial Pressure of O2 and CO2 in the body
The difference between any two pressures is called :
Diffusion gradient =
60 mmHg
In alveoli
PO2 = 100mmHg
In blood
PO2 = 40mmHg
The bigger or steeper the diffusion gradient the quicker diffusion will occur.

19. Gaseous Exchange Internal respiration
O2 diffuses from systemic capillaries into cells
CO2 diffuses from cells into systemic capillaries
External Respiration
CO2 diffuses from pulmonary capillaries into alveoli
O2 Diffuses from alveoli into pulmonary capillaries

20. Internal Respiration
Internal respiration occurs because of the following factors:
Available surface area, which varies in different tissues.
Partial Pressure gradient
Rate of blood flow varies (e.g. metabolic rate of tissue)

21. Internal Respiration CO2 and O2 Exchange
This is ONE capillary surrounding a tissue cell.

22. External Respiration
External respiration occurs because of the following factors:
The partial pressures of gases in the alveoli differ from those in the atmosphere.
Humidification of inhaled air
Gas exchange between alveoli and pulmonary capillaries
Atmosphere (mmHg)
PO2
159
PCO2
0.3
PH2O
3.5

23. Factors Influencing External Respiration
Efficient external respiration
depends on 3 main factors:
Surface area and structure of the respiratory membrane
Partial Pressure gradients
Matching alveolar airflow to
pulmonary capillary blood
flow.
Partial pressure gradients affect gas exchange between the alveoli and pulmonary capillaries.

24. Gaseous exchange at the alveoli
The alveoli are tiny air sacks inside the lungs.
A dense capillary network supplies them with oxygen. Their walls are extremely thin (only one cell thick) and together they create a huge surface area to allow for a greater uptake of oxygen.
Gases can easily pass through the thin walls and travel into the blood stream.
With training this process of gaseous exchange becomes more efficient and therefore improves performance.

25. Gaseous exchange at the alveoli
Gaseous exchange is promoted through a number of bodily functions.
Capillaries very near to alveoli, so diffusion distance is very short.
Large surface area of alveoli allows diffusion to take place.
Vast network of capillaries surround alveoli which increases surface area further.

26. Gaseous exchange at the alveoli
Gaseous exchange takes places at two different sites.
1. Lungs
Between alveoli and surrounding alveolar capillaries.
2. Muscles
Between muscles and surrounding blood capillaries.

27. How is Ventilation Controlled?
The nervous system can increase or decrease the rate, depth and rhythm of breathing.
The respiratory centre located in the medulla oblongata of the brain controls breathing.
An increased concentration of carbon dioxide in the blood stimulates the respiratory centre to increase respiratory rate.

28. Control of Ventilation
Respiratory Control Centre
The inspiratory centre sends out impulses via the phrenic nerve to the inspiratory muscles.
The expiratory centre stimulates the expiratory muscles during exercise, when stretch receptors detect changes in the rate and depth of breathing.

29. Control of Ventilation
During exercise, conditions in the body change. These changes are detected by:
Chemoreceptors - which detect changes in pH - blood acidity increases as a result of an increase in the plasma concentration of carbon dioxide and lactic acid production.
Baroreceptors - which detect an increase in blood pressure.
Proprioceptors - which detect movement.
Photo by: © LOCOG

30. Carbon dioxide
When exercise stops, carbon dioxide levels, blood pressure and muscle movement all decrease. This is detected by the receptors, which send impulses to the cardiac control centre.
An impulse is then sent through the parasympathetic system which stimulates the sinoatrial node and heart rate decreases.

31. Impact of a poor lifestyle
A sedentary lifestyle is a type of lifestyle with no or irregular physical activity. This include sitting, reading, watching television, playing video games, and computer use for much of the day with little or no vigorous physical exercise.
Photo by: ©
A sedentary lifestyle can impact hugely on the respiratory system.

32. Impact of a poor lifestyle
Photo: © Stock.xchng.
Think. Pair. Share - What effects does smoking have on the respiratory system?

33. Impact of a poor lifestyle
Over time smoking reduces the lungs surface area and destroys the alveoli structures.
This will reduce gaseous exchange and make the individual feel short of breath and reduce the oxygen transport capacity.
Photos: © Stock.xchng.

34. Apply it! The Respiratory system What has stuck with you?
Explain the principle of diffusion and how it can be seen in the respiratory system.
Describe what is meant by the terms ‘tidal volume’ and ‘minute ventilation’
How is pulmonary ventilation controlled by the body?
What is the affect of a poor lifestyle on the respiratory system?
The Respiratory system
Photos by: LOCOG

35. Practice it!
Exam questions
Identify which one of the following statements defines expiratory reserve volume [1 mark]
A The amount of air breathed in or out per breath
B The amount of air left in the lungs after maximal expiration has occurred
C The amount of air that can be forcibly expelled after a
normal breath
D The amount of air that can be forcibly inspired at the end of a breath

36. Practice it! Exam questions
2. While running, a performer will experience changes in lung volumes.
Complete Table 3 below to show how the tidal volume, inspiratory reserve volume and expiratory reserve volume change during exercise [3 marks]

37. Practice it! Exam questions
3. Explain how the gas exchange system operates at muscles [4 marks]

38. Practice it! Marks Scheme: C
A. Tidal volume – increases B. Inspiratory reserve volume – decreases C. Expiratory reserve volume – decreases
A. Process of diffusion – high concentration/partial pressure to low/down a diffusion gradient B. Requires thin/permeable membranes/short distance C. High pO2 in blood/low pO2 in muscles and oxygen moves into muscles D. Low pCO2 in blood/high pCO2 in muscles and carbon dioxide moves into blood E. Oxygen into myoglobin/ (disassociates) from haemoglobin F. Carbon dioxide dissolves in plasma/ combines with haemoglobin/forms bicarbonate ion