1.1.b. Respiratory system GapFill

As exercise intensity increases, so does the volume of oxygen inhaled due to a combination of increases in breathing   intensityforcefrequencycount and  tidalexpiratory reserveresidualwave volume. This allows more oxygen to become available for gaseous exchange at the alveoli. The process of gaseous exchange is facilitated by two key features that occur during exercise:

1. Greater diffusion   distanceimbalancegradientdifference - The difference between the high concentration (partial pressure) of oxygen in the alveoli and the low concentration in the   veinsheartvenuolescapillaries increases, causing a proportional increase in the rate of diffusion. In contrast, the partial pressure of oxygen at the muscle becomes increasingly lower, resulting in a greater rate of oxygen extraction. On the other side of the exchange, the increase in   energycarbon dioxidewateroxygen produced at the muscle during exercise is transported in the blood to the lungs, where there is a greater partial pressure in the capillaries compared to the alveoli. This results in a greater diffusion rate of carbon dioxide from the capillaries to the alveoli for   inhalationexhalationconductionconvection into the atmosphere.
2. Greater dissociation of oxyhaemoglobin - The haemoglobin molecule is responsible for carrying  nutrientscarbon dioxideoxygenproteins in the blood. It becomes saturated under high concentrations at the lungs, and readily dissociates at low concentrations in the muscle.