Internal and external respiration during
exercise.
External respiration during exercise.
We use more O2 during exercise so the blood arriving at the alveoli
(lungs) has got lower levels of O2. The alveoli contain high levels of
O2. Therefore the partial pressure of O2 in the alveoli is high,
where as the partial pressure of O2 in the capillary (blood) is low.
This steep diffusion gradient increases the rate and amount of O2
diffusion into the blood. This causes almost all of the haemoglobin to
be bonded with O2.
During exercise a by-product of energy production is CO2 within the
muscle – this needs to be removed. The blood returning to the alveoli
has a high partial pressure of CO2 – the alveoli contain a very low
Partial pressure of CO2. This creates a steep diffusion gradient
which again increases the rate and amount of CO2 diffused from the
blood to the alveoli (through the capillary and alveoli wall).
Internal respiration during exercise.
There is a high PP of O2 within the capillary at the muscle. There is
very little O2 within the muscle tissue (used during exercise).
There is a high PP of CO2 within the muscle tissue with a low PP of
CO2 within the blood (capillary).
Both are high diffusion gradients – so increased rate and amount of
diffusion.
This process of the haemoglobin giving up its O2 more readily is
known as oxygen dissociation. So important during exercise!
There are four factors which help this process:
1 Increase blood temperature. Heat generated when exercising.
2 Decrease in PP of O2 within muscle increasing O2 diffusion
gradient. O2 used up through energy production during exercise.
3 Increase in PP of CO2 increases O2 diffusion. CO2 produced as a
by-product of energy production.
4 Increase in acidity (lower PH). Production of lactic acid lowers
PH.
The affect of the haemoglobin giving up the O2 more readily
increases the O2 supply to the working muscles which delays
fatigue /allows for higher intensity work / allows work for longer
duration.
Diagram below shows the O2 dissociation curve.
See p44 in revision guide or p108-9 in textbook.