IB SEHS 2.1.5-2.1.7

Explain the process of gaseous exchange at the alveoli.

Gaseous exchange occurs in the alveoli by a process called diffusion, which occurs between the surface of alveoli and pulmonary capillary beds. Oxygen, once inhaled into the lungs, is passed from the alveoli into the bloodstream for distribution to the rest of the body. This occurs because there is a higher concentration of O2 in the alveoli than in the blood. There, O2 diffuses across to the capillaries where there is a lower concentration. At the same time, CO2 goes from the high concentration in the capillaries to a low concentration in the alveoli and is breathed out during exhalation. (Partial pressure= concentration)

Outline the role of hemoglobin in oxygen transport

Most (98.5%) of oxygen in the blood is transported by hemoglobin as oxyhemoglobin within red blood cells. Hemoglobin is the protein that allows oxygen to bind to a red blood cell. Hemoglobin contains a central Iron ion, which can hold up to 4 oxygen atoms per heme. These oxygen atoms are then diffused into the tissues once they reach their target.

describe nervous and chemical control of ventilation during exercise

Ventilation increases as a direct result of increases in blood acidity levels (low pH) due to increases carbon dioxide content in the blood detected by the respiratory center (CO2 is usually transported as bicarbonate). This results in an increase in the rate and depth of ventilation. The respiratory center is in the medulla; this sends messages to the ventilatory muscles Neural control of ventilation includes lung stretch receptors, muscle proprioceptors, and chemoreceptors.