Respiratory System Flashcards
What is anatomic dead space?
In terms of lung capacity.
What are terminates?
Boyle’s Law / 1st Gas Law and breathing
At a constant temperature, the pressure of a gas is inversely proportional to its volume.
- Inhalation: The diaphragm contracts and moves down, increasing lung volume. This lowers pressure inside the lungs, drawing air in.
- Exhalation: The diaphragm relaxes and moves up, reducing lung volume. This increases pressure, forcing air out.
P₁V₁ = P₂V₂
E.g. when scuba divers ascend too fast, the rapid gas expansion in lungs can cause barotrauma (lung overexpansion injury).
Fick’s Law
The rate of gas diffusion depends on surface area, membrane thickness, and pressure gradient.
In the lungs:
- More surface area (like in healthy alveoli) = better gas exchange.
- Thicker membranes (like in pneumonia or pulmonary fibrosis) = slower diffusion.
Fitness Assessment, Week 3
What is Fick’s Equation?
Psst… It involves Q!
VO2max = SV x HR x (a -vO2 diff)
a -vO2 diff - arteriovenous oxygen difference
SV x HR can also be written as cardiac output, or Q.
Fitness Assessment, Week 3
What is Respiratory Exchange Ratio?
The Respiratory Exchange Ratio (RER) is a key parameter measured during VO₂ max testing that provides insight into fuel utilization during exercise. VCO2 / VO2
VO₂ = Volume of O2 consumed
VCO₂ = Volume of CO2 produced
RER will value from 0.7 to >1.1 throughout testing, depending on the shift from glycolysis to glucose.
Law of partial pressures…
Dalton’s law
The total pressure of a gas mixture is the sum of the partial pressures of each individual gas.
At sea level, atmospheric air = 760 mmHg, composed of:
- O₂ ~ 21% (160 mmHg)
- N₂ ~ 78%
- CO₂ ~ 0.04%
In the alveoli, O₂ has a higher partial pressure than in the blood, so it diffuses into the capillaries, while CO₂ (higher in blood) diffuses into the lungs to be exhaled.
Ptotal = P₁ + P₂ + P₃
At high altitudes, atmospheric pressure is lower, reducing O₂ partial pressure → harder for oxygen to diffuse into blood → hypoxia (oxygen deprivation).
Can you describe the sequence of human inspiration?
- The diaphragm contracts, moving down.
- This increases thoracic volume, reducing pressure in it.
- External intercostals contract.
- Internal intercostals and abdominis relax.
Can you describe the sequence of human expiration?
- The diaphram relaxes, expanding in size and consequentially increasing pressure.
- Thoracic volume decreases, resulting in higher pressure.
- External intercostals relax.
- **Internal intercostals contract. **
- Abdominis contracts as well.
Can you name the key pulmonary volumes?
By the way - there’s four 😉
- Tidal volume
- Inspiratory Reserve Volume
- Expiratory Reserve Volume -
- Residual volume
What’s tidal volume?
Tidal volume - the volume of an average, normal breath. In an adult, about 500ml.
Think lungs!
What’s IRV?
I for…
Inspiratory Reserve Volume - the extra air you can inhale after a normal breath, about 3L.
Think lungs!
What’s ERV?
E for…
Expiratory Reserve Volume -the air you can forcefully exhale after a normal breath out, about 1.2L.
What’s residual volume?
Residual volume - the air that always stays in your lungs even post exhalation, about 1.2L.
What’s the difference between lung capacities and lung volumes?
Each volume is a separate ‘chunk’ of air, while capacities are combinations of multiple volumes.
What is Vital Capacity and its constituents?
Vital for Life…
The biggest breath you can take in and then forcefully breathe out; the lung power you actually use.
TV + IRV + ERV
What is Total Lung Capacity and its constituents?
The absolute max air your lungs can hold, at full stretch.
Vital Capacity + RV
What is Inspiratory Capacity and its constituents?
The max amount you can inhale after a normal exhale.
TV + IRV
Hint: more than just RV!
What is Functional Residual Capacity and its constituents?
The air left in your lungs after a normal breath out.
ERV + RV
