A1.3 - Transport

What is the Respiratory System?

The system which enables the transport and exchange of oxygen for use in cellular respiration

What is diffusion?

When a substance moves from an area of high pressure to an area of lower pressure.

What is the process of breathing during rest?

Breathing in:

1. The diaphragm contracts and pulls downwards

2. The lungs are stretched, increasing in volume

3. The pressure in the lungs is now greater than the pressure of air in the atmosphere

4. Air flows into the lungs via diffusion to balance the pressure gradient.

Breathing Out:

1. The diaphragm naturally relaxes, returning to its normal position

2. The volume of the lungs decreases

3. The pressure of what is now carbon dioxide in the lungs becomes less than the pressure of carbon dioxide in the atmosphere

4. Carbon dioxide leaves the lungs via diffusion.

How is breathing during exercise slightly different than during rest?

Because muscles such as the shoulders, abdomen and intercoastal muscles (chest wall) are contracted and expanded to help speed up the expansion and compression of the lungs, in-turn speeding up breathing.

When air is inhaled, where does it pass through?

The nasal and oral passageways (conducting airways) and to the trachea and eventually bronchi, which lead to the alveolus.

What do the alveolus do?

They are small air sacs with thin walls, allowing for the diffusion of oxygen into the blood, and the diffusion of carbon dioxide from the blood into the alveoli.

What is gas exchange?

The transfer of oxygen and carbon dioxide with tissues.

What are lungs ideal for gas exchange?

• The alveoli create a large surface area (50 - 100m²)

• Have a good blood supply

• The alveoli are close to the blood for efficient diffusion

What can and can´t lung volumes be impacted by?

They are impacted by age, sex and body size, and can´t be impacted by training.

What is the process of gas exchange in the body?

To Blood:

1. Air with high oxygen and low carbon dioxide content is breathed in, reaching the alveolus

2. Blood pumped from the tissues to the heart is high in CO₂ and low in O₂.

3. When passing by the alveolus, the O₂ diffuses into the blood, while the CO₂ diffuses from the blood into the alveolus.

To Tissues:

4. Blood high in O₂ and low in CO₂ is pumped to tissues.

5. These tissues are high in CO₂ as they´re producing it and low in O₂

6. O₂ from the blood diffuses into tissues, and CO₂ from tissues diffuses into blood.

7. This blood goes back to the heart, where it meets the alveolus (Step 3)

What happens to O2 consumption during exercise?

It is increased to ensure the pressure of O₂ in the alveoli is greater than that in the blood to permit diffusion.

What is minute ventilation (V_E)?

The volume of air exhaled per minute (and therefore inhaled as well). It is the product of the Tidal Volume VT (the size of each breath) and the BF (number of breaths per minute)

V_E (1 min^-1) = V_T (1 breath^-1) x B_F (breaths min^-1)

What happens to V_E during exercise?

It increases as V_T and B_F increase. This helps maintain resting gas pressures and sustain oxygen supply to active tissues, maintaining homeostasis.