Fill in the blanks: When the alveolar Po₂ decreases, the pulmonary arterioles_____. When the arteriolar Pco₂ increases, the bronchioles_______.

Video transcript

Everyone. Let's take a look at this question together. When an alveolus is insufficiently ventilated, what happens to the alveolar partial pressure of oxygen and the pulmonary arterial serving that alveolus? Is it answer choice. A the partial pressure of oxygen rises and the arterial constricts, answer choice B, the partial pressure of oxygen drops and the arterial constricts. Answer choice C the partial pressure of oxygen rises and the arterial dilates or answer choice d the partial pressure of oxygen drops and the arterial dilates. Let's work this problem out together to try to figure out which of the following answer choices best explains what happens to the alveolar partial pressure of oxygen and the pulmonary arterial that is serving that alveolus when it is insufficiently ventilated. So, in order to solve this question, we have to recall what we have learned about what it means to be insufficiently ventilated, to determine what happened to the alveolar partial pressure of oxygen and the pulmonary arterial that is serving that insufficiently ventilated alveolus. And we can recall that when we say insufficiently ventilated, we are saying that there is not enough fresh air reaching the alveolus or efficient gas exchange and as a result of not enough fresh air reaching that alveolus, there is no access to oxygen which results in the oxygen levels decreasing. So the alveolar partial pressure of oxygen levels drop. And as a result of those levels dropping, the alveolus responds by constricting to redirect blood flow away from the poorly oxygenated areas of the lungs. So we know that when an alveolus is insufficiently ventilated, the alveolar partial pressure of oxygen drops and the arterial that is serving that alveolus constricts, which means that answer choice B is the correct answer since the partial pressure of oxygen drops and the arterial serving that alveolus constricts and all other answer choices are incorrect. I hope you found this video to be helpful. Thank you and goodbye.