Gas Exchange and Respiratory Physiology Quiz

The primary driver of ventilation is carbon dioxide (CO2) levels in the blood. If CO2 levels rise (hypercapnia), it stimulates breathing to expel the excess CO2. This is called the hypercapnic drive. In some cases, oxygen (O2) levels may also influence ventilation, but this is generally less significant than the CO2 drive. This is called the hypoxic drive.

Gas exchange at the tissue level happens in the capillaries, where blood carrying oxygen from the lungs comes in contact with the cells of the body. Oxygen is then released from the blood and diffuses into the cells, while carbon dioxide from the cells diffuses into the blood to be transported back to the lungs.

Factors affecting the rate of gas exchange include the surface area of the membrane, the pressure difference between the gas in the lungs/blood and the gas in the blood/cells, the amount of time the gases are exposed to the membrane, the thickness of the membrane, and the diffusibility of the gas (how easily it moves across the membrane).

The demand for ventilation is primarily determined by the metabolic needs of the body's tissues. When tissues are working hard, they need more oxygen and produce more carbon dioxide. This increased demand triggers the body to breathe faster and deeper to deliver more oxygen and remove excess carbon dioxide. The overall health of the body also plays a role, as conditions like lung disease, anemia, or a fever can affect how efficiently the body uses oxygen and removes carbon dioxide, influencing ventilation.

The right heart pumps deoxygenated blood from the body to the lungs. This blood has a high concentration of carbon dioxide and is low in oxygen. The right heart's job is to deliver this blood to the lungs where it can be oxygenated and release the carbon dioxide.