The Role of Probability. Basic Concepts of Probability. A probability is a number that reflects the chance or likelihood that a particular event will occur. Probabilities can be expressed as proportions that range from 0 to 1, and they can also be expressed as percentages ranging from 0% to 100%.
Thus, when people hypoventilate (i.e. causing an increase in CO2) this causes the pH in your blood to decrease, making it more acidic. (and when hyperventilation occurs, O2 is increased, which causes an increase in pH - making blood more basic).
So yawning may function in altering the first two variables: increasing arterial blood flow and allowing the flow of cooler blood to the brain.. To answer the question of what happens in the body is fairly straightforward: When you yawn, your mouth gapes open and you inhale deeply, finishing with a short exhalation. During this time, the muscles around your skull contract and stretch and you take in ambient air.