Question

2. (a) State and explain the changes in the lung volume, the alveolar pressure (Palv) and
airflow between the atmosphere and the lungs during passive exhalation.

(b) What happens to the ventilation rate during exercise? Briefly describe and explain
how the chemoreceptors work during exercise.

Answer 1

Answer 2:

a: Exhalation is a passive process i.e no energy is required during exhalation. During passive exhalation the diaphragm and intercostal muscles relaxes and the lungs recoil due to elasticity of lungs which causes decreases the lung volume. This causes increase in interpulmonary pressure above the atmospheric pressure due to which pressure gradient is formed and air moves out from the lungs. Due to decrease in volume of the lungs the alveolar volume also decreases and the alveolar pressure increases above the atmospheric pressure.

b: During exercise the muscles requires more oxygen and for this ventilation rate increases so that more oxygen can be added to the blood during respiration and more oxygenated blood can be pumped by the heart to the exercising muscles. Chemoreceptors are of two types i.e Peripheral and Central Chemoreceptors. Peripheral chemoreceptors are located in carotid and aortic bodies which take part in ventilation during exercise by responding to changes in blood concentration of oxygen and carbon dioxide and also blood pH. Central Chemoreceptors which are located in the medulla of the brain monitors pH and carbon dioxide level in the cerebrospinal fluid. Peripheral and central Chemoreceptors work in tandem together in maintaining cardiorespiratory homeostasis. These Chemoreceptors monitors oxygen levels in blood and then transmits the signal to vasomotor center in the medulla of the brain which modulates the ventilation rate.