PSL201Y1 Lecture Notes - Lung Volumes, Tidal Volume, Acetyl-Coa
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Why do we breathe?
The process of producing energy consists of taking fats and
carbodydraytes, breaking these sugars and fats down so that we end
up with hydrogen ions. Hydrogen ions facilitate the production of ADP.
ADP is converted into ATP, the energy substance. At the end of the
process, we still wind up with hydrogen ions. When we hold our
breath, there is a rise in hydrogen ions which is problematic.
Therefore, oxygen is necessary to come into the system through
respiration, combine with the hydrogen ion and produce water. The
process of producing energy is done though the Krebs cycle.
500 ml is approx the volume of air that we breathe in and out at a
time during rest. This is called the Tidal volume. However, the
composition of the air is changed. We use some of the oxygen and
replace it with some of the CO2 coming off the Krebs cycle. In a
minute, we breathe about 20 times.
Therefore V = total volume frequency = 500 (20)=10 000 ml or 10
Vital capacity is the maximum volume of air possible to inhale with one
breath. There is a large difference between the vital capacity and the
total volume at rest.
Resistance to air flow is proportional to 1/(radius)4. This signifies that
a small decrease in the air waves leads to a large increase in
resistance. In other words, taking bigger breaths will decrease the
amount of air coming out because we cannot breathe in and out at the
same time. However, we possess the ability to breathe out more than
we can breathe in. This is called expiratory reserve volume. This
reserve volume exists to expel unwanted items (ex: peanut stuck in
throat) and to continuously supply oxygen to the pulmonary
bloodstream. In addition to the expiratory reserve volume, there is the
residual volume which is the oxygen left in the lungs that we are not
capable of breathing out. The air that we breathe in after a period of
rest is called the inspiratory reserve volume while the air that we
breathe in after a period of rest then breathe out is called vital
Timed vital capacity is the measure of the maximum amount of air
during a forced vital capacity determination that can be expelled in a
given number of seconds. For those with smaller airwaves, it would
take a longer time for the air to be expelled from the lungs.