Lecture 23 - Respiratory Physiology #2 Flashcards
What is the amount of air breathed in and out during one normal breath (one normal respiratory cycle)
Tidal volume (VT)
what is the volume of air that remains in the lungs after a complete and forceful expiration?
Residual Volume (RV)
What is the amount of air that you can inspire beyond what you breathe in during a normal breath?
inspiratory reserve volume
what is the amount of air you can expire beyond what you breathe out during a normal breath?
expiratory reserve volume
what is the maximum amount of air that can be inspired after the maximum amount of air has been expired (the most that you can breathe in and out with minimal effort)
vital capacity
vital capacity + residual volume = ?
total lung capacity
residual volume + expiratory reserve volume = ?
functional residual capacity
the amount of air in the lung after a normal expiration is known as:
the functional residual capacity. it is the lung volume that occurs when the chest wall and lung are in equilibrium
T or F: energy is used during breathing
True! Energy is needed to overcome both contractile forces of the lungs, and the resistance to airflow found in the respiratory system
what is compliance?
It is a measure of distensibility of the lung, and is determined by measuring the change in lung volume as a result of a change in pressure
in the mid-range of pressure, compliance is:
high, as the change in volume is large for a given change in pressure
at high pressures (for example, at the end of inspiration) compliance is:
low, as the lungs are less distensible
the term describing the attractive forces between atoms/molecules is called:
surface tension
alveolar surface tension can be calculated by what equation?
P = 2T/r, where:
P is the pressure inside the alveolus
T is the tension on the inner surface
r is the internal radius of the alveolus
When the radius of an alveolus is small, you need ____ pressure to overcome the surface tension in order to expand the alveolus
MORE.
the substance that reduces the number of water molecules that can attract each other, and therefore reduces the work required to breathe, is called:
surfactant
pulmonary surfactant is synthesized by:
type II alveolar epithelial cells (secretory cells)
what is the percentage of lipid to protein in pulmonary surfactant?
70% lipid
30% protein
at the end of expiration, the alveolus is what size? How does this effect the surfactant?
the alveolus is at its smallest size (r is low), and therefore the surfactant becomes more concentrated on the surface. this greatly reduces the surface tension (T)
what are two functions of surfactant at the end of expiration?
- it counteracts the effects of the small radius, so that the pressure at the start of inspiration is not too high to open
- it reduces the surface tension, which stabilizese the alveolus so that when it is small, the lung doesn’t collapse
at the end of inspiration, what size is the alveolus? What, in turn, happens to the surface tension?
alveolus is at its largest size. as a result, surfactant spreads out and becomes less concentrated, and surface tension (T) increases.
How does increased surface tension aid in the end of inspiration?
It assists the elastin and collagen fibers by creating an upper limit to the expansion of the lungs, while also providing some recoil so that expiration can be a passive process
what is the equation for airway resistance?
8nl/(pi)r^4,
where:
n = viscosity of the fluid
l = length of tube
r = radius of the tube
what has the greatest effect on the resistance to air flow?
airway diameter. this is because radius is to the power of four in the denominator of poisuilles law, meaning that if the radius is halved, the force must increase by 16x to maintain constant flow
The largest resistance to airflow occurs at which branches?
Branches 4 and 5. This is due to the turbulence as the branches first divide
Why does airway resistance go down if the radius of the airways gets progressively smaller?
while the diameter of each individual tube gets smaller and smaller with each bifarcation, the total diameter of all the airways increases exponentially
Which has lower resistance to airflow: the respiratory zone, or the conducting zone?
the respiratory zone, which makes it easier to breathe
What are the three gas laws?
Volume = constant / Pressure
Volume = constant x temperature
dissolved amount of a gas = pressure x solubility coefficient
the pressure exerted by a specific gas when it is in a mixture of gases is known as:
partial pressure
which law states that the pressure exerted by one gas is independent of the pressure exerted by other gases, and that the sum of all individual gas pressures is equal to the total gas pressure?
Daltons Law
how do you calculate partial pressure (P) of a gas?
fractional concentration (%) of the gas x the total gas pressure
What are the notations for arterial, venous, and alveolar pressures of a gas?
Pa = arterial pressure
Pv = venous pressure
PA = alveolar pressure
True or False: if compartment A has a higher partial pressure of oxygen than compartment B, but the total gas pressure of A is lower than B, oxygen will move against its concentration gradient so that the total gas pressures of A and B reach equilibrium
False. regardless of the total pressure of a gas mixture, individual gases diffuse in response to their own gradients (from areas of high partial pressure to areas of low partial pressure)
Diffusion across a membrane follows what law?
Fick’s law:
Vgas = A x D x (P1 -P2)/T, where:
A = surface area of the membrane
D = the diffusion coefficient for the gas
P1 and P2 = partial pressures on each side of the membrane
T = thickness of the membrane
How can the PO2 be so high as a driving force, while PCO2 remains low?
CO2 is soluble in water, while O2 is not as soluble.
For optimal gas exchange, surface area should be:
large
For optimal gas exchange, the diffusion coefficient should be:
fast
For optimal gas exchange, the difference between the two partial pressures should be:
large
For optimal gas exchange, the thickness of the membrane between the two partial pressures should be:
thin
