Ventilation

chapters 13 and 14

where does gas exchange happen

alveoli

where does CO2 in alveoli come from

waste product from cells breaking down CHOs and fats

where does oxygen go from the alveoli

goes into blood to the tissues for oxidative phosphorylation

role of O2 in ETC? then what happens to it?

final electron acceptor in ETC, then is converted to H2O → why expired O2 is less than inspired O2

how does the body move air in and out of the lungs?

respiratory and accessory muscles contract to expand the ribs and increase the pressure gradient between the lungs and the atmosphere

(negative pressure within the lungs to pull air in, positive pressure in the lungs to push air out)

how to the ATP demands of breathing change with exercise

breathing more forcefully and at a higher rate requires more ATP to accommodate the increased work load of the respiratory muscles

how do increased ATP demands in the muscle affect breathing?

high ATP demands mean high energy transfer rates, which means a high production of CO₂ needing to be expired and more O₂ needing to be consumed in order to generate energy

does breathing impact exercise performance

yes, because there is an ATP cost to breathing and because ventilation is highly linked to metabolism

how to calculate how much air one breathes in one minute

V_E =f_{b ^x} V_T

Volume expired = breathing frequency x tidal volume

average tidal volume (V_T)

500mL

Average breaths per minute (f_b)

12bpm

Concentration of oxygen in atmosphere

20.93%

concentration of carbon dioxide in the atmosphere

0.03%

how to calculate partial pressure

concentration of gas (%) x total pressure

pressure of 1 standard atmosphere (1 atm)

760mmHg

consequences to ventilation at high altitude

altitude means atmospheric pressure has dropped to about 220mmHg

therefore, even though the concentration of O2 is still the same as it was at sea level, its partial pressure (PO₂) is very low

this means we inhale much less O2 and need to work harder to get the same amount of air and oxygen in, but its super easy to push CO2 out

have to create super negative pressure in lungs to create a gradient high enough to inhale

what does RER stand for

respiratory exchange ratio

how to calculate RER

VO₂/VCO₂

open-circuit spirometry

measures oxygen uptake and CO2 production to infer energy expenditure

subject inhales ambient (room) air

equation used in open-circuit spirometry

hyperventilation

increase in ventilation that is more than what is needed by metabolism to get the O2 in and the CO2 out

dyspnea

subjective SOB, seen with asthma, COPD

at a high pressure differential between two places, how does gas move

via diffusion, gas moves very quickly from high pressure to low pressure

at a halfway point to reaching equilibrium, how does gas move between two places

via diffusion, high rate of gas moving from high to low pressure, with some gas moving slowly from low to high pressure

gas movement at equilibrium between two places

via diffusion, gas moves equally in and out of each place

which is able to diffuse faster, O2 or CO2

CO2 because it is more soluble

how long does blood spend in the pulmonary capillary at rest?

about 0.75s

how long does blood spend in the pulmonary capillary at maximal exercise?

about 0.4s

factors that impair fas transfer capacity at the alveolar-capillary membrane

what impact do these have on gas equilibrium?

1. buildup of a pollutant layer that thickens the alveolar membrane → slows diffusion

2. reduction in alveolar surface area

these factors make it take longer to reach alveolar-capillary gas equilibrium

why does the blood spend less time in the pulmonary capillaries when exercising compared to at rest?

is this a problem?

because of the increased speed of blood flow

in a healthy person, there is still enough time for gas exchange to occur. but if they have a compromising condition, this will not be enough time and ventilation will be limited

how does increased oxidative phosphorylation alter the partial pressures of O₂ and CO₂ at different locations in the body

Venous blood leaving muscle

High oxidative metabolic demands mean higher O₂ consumption. This results in more O₂ turning into H₂O, and a lower PO₂. PCO₂ goes up as the production rate is higher.

Arterial blood

Partial pressures here remain the same because we are able to increase RR to accommodate the higher O₂ needs and higher CO₂ levels that need to be expired

How does the body maintain homeostasis by minimizing changes in gas partial pressures

The body increases respiratory rate to better inspire O₂ and expire CO₂. This maintains the partial pressure of arterial blood

What ventilation changes can we measure in the lab with increased exercise intensity

oxygen expired

carbon dioxide expired

VO₂

VCO₂

RER

substrates being used

when might lungs limit exercise performance

mostly only when the lungs are compromised. otherwise, we are very good at breathing

Hb in blood

15g per 100mL of blood

150g per 1L of blood

amount of O2 in blood

20mL per 100mL of blood

200mL per 1L of blood

why do men have more RBC and Hb than women

testoterone

equation for blood O2 capacity

Hb x HbO₂ capacity

how much O2 carried by Hb at full saturation with normal Hb levels

20mL O2 with each 100mL blood

200mL O2 with each L of blood