Ventilation in Mammals

Question 1

Describe the process of Inhalation/Inspiration

Answer 1

1. External intercostal Contract - Ribcage moves UPwards & OUTwards
2. Diaphragm muscle Contract - Diaphragm flattens
3. Thorax volume increases, Lung pressure decreases
4. Air flows into lungs
5. Elastic fibres between alveoli stretch, helps move air in
6. Active process, requires energy

Question 2

Describe the process of Exhalation/Expiration

Answer 2

1. External intercostal Relax - Ribcage moves DOWNward & INward
2. Diaphragm muscle Relax - Diaphragm becomes curved
3. Thorax volume decreases, Lung pressure increases
4. Air is forced out of lungs
5. Elastic fibres between alveoli recoil, helps push air out
6. Passive process - no energy required

Question 3

Describe the process of FORCED Exhalation/Expiration

Answer 3

• Internal Intercostal muscles contract
• Pulls ribcage down and inwards
• forces air out of lungs
• External intercostal muscles relax, antagonistic

Question 4

Tidal Volume (TV)

Answer 4

The volume of air in each breath (0.4 dm3)

Question 5

Vital Capacity

Answer 5

Maximum volume of air that can be breathed in and out

Question 6

Breathing Rate

Answer 6

Number of breaths taken per minute (BPM)

Question 7

Oxygen Uptake

Answer 7

The rate at which organisms use up oxygen (

Question 8

Draw and Label a spirometer graph

Answer 8

• y-axis = volume of gas in lungs /dm3
• x-axis = Time /seconds
• Residual volume at bottom (air that can’t be expelled)
• Expiratory reserve volume (ERV) - deep breath out
• Tidal volume (TV) in middle
• Vital capacity (VC) highest point to ERV
• Inspiratory reserve volume (IRV) - deep breath out
• Total Lung capacity - everything top to bottom

Question 9

How do spirometers give readings of TV, VC, BPM and Oxygen uptake?

Answer 9

• Spirometer oxygen chamber with movable lid
• Person breathes through a tube connected to the oxygen chamber
• As person breathes in and out, chamber lid moves up and down
• Movements recorded by pen attached to lid, writes on rotating drum to make spirogram
• Or spirometer hooked to a motion sensor to produce electronic signal picked up by data logger
• In the tube person breathes into, soda lime absorbs CO2