Systems Biology
The respiratory system serves several important functions, including gas exchange, regulation of body temperature, and control of blood pH. Gas exchange occurs in the alveoli of the lungs and the tiny capillaries that surround them. The exchange involves the diffusion of carbon dioxide (CO2) from capillary blood into alveolar air and the simultaneous diffusion of inhaled oxygen from alveolar air into capillary blood. This process is passive and is driven by the differential partial pressures of oxygen and CO2 between the capillary blood and alveolar air. The concept of partial pressure is explained by Henry's Law, which states that the amount of dissolved gas in a liquid is proportional to the partial pressure of gas above the surface of the liquid.
The respiratory system also plays a small role in thermoregulation, or the regulation of the body's internal temperature. This occurs through the dilation and constriction of capillary beds in the nose and trachea, which help dissipate heat or conserve it, depending on the body's needs. In some animals, evaporation of water and mucus secretions through the respiratory system facilitates heat loss during panting. Additionally, the respiratory system helps control blood pH by adjusting the respiratory rate in response to changes detected by chemoreceptors in the brainstem. When blood pH is too low, the respiratory rate increases to rid the body of excess CO2, raising blood pH. Conversely, decreased respiration conserves CO2 to lower blood pH when the pH becomes too high.
Lesson Outline
<ul> <li>Functions of the respiratory system</li> <ul> <li>Gas exchange</li> <li>Regulation of body temperature</li> <li>Control of blood pH</li> </ul> <li>Gas exchange</li> <ul> <li>Occurs between alveoli and capillaries</li> <li>CO<sub>2</sub> diffuses from capillary blood into alveolar air and is exhaled</li> <li>Oxygen diffuses from alveolar air into capillary blood and binds to hemoglobin in red blood cells</li> <li>Passive process (diffusion) due to differential partial pressures of O<sub>2</sub> and CO<sub>2</sub></li> <li>Henry's Law - amount of dissolved gas in a liquid is proportional to the partial pressure of gas above the surface of that liquid</li> </ul> <li>Thermoregulation (regulation of body temperature)</li> <ul> <li>Minor role in respiratory system</li> <li>Capillary beds in nose and trachea adjust blood flow to dissipate or conserve heat</li> <li>Evaporation of water and mucus secretions aids in heat loss (panting)</li> </ul> <li>Control of blood pH</li> <ul> <li>Chemoreceptors in brainstem detect changes in arterial CO<sub>2</sub> concentration</li> <li>Respiratory rate changes based on blood pH</li> <ul> <li>Low blood pH (acidic) - increase in respiratory rate to expel more CO<sub>2</sub></li> <li>High blood pH (basic) - decrease in respiratory rate to retain more CO<sub>2</sub></li> </ul>
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FAQs
Alveoli are small air sacs in the lungs where gas exchange occurs. They are surrounded by a network of tiny blood vessels called capillaries. During gas exchange, oxygen from the air in the alveoli diffuses into the capillaries to be used in the body, while carbon dioxide from the blood in the capillaries diffuses into the alveoli to be expelled through expiration. This process is essential for delivering oxygen to the body's tissues and removing waste products, ensuring proper cellular functioning.
Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. During the gas exchange process, oxygen and carbon dioxide move by diffusion across the thin walls of the alveoli and capillaries, which are only one cell layer thick. Oxygen in the alveolar air diffuses into the blood in the capillaries, where its concentration is lower, while carbon dioxide in the capillaries diffuses into the alveolar air, where its concentration is lower. This passive process is driven by the concentration gradients of the gases and enables effective gas exchange.
Thermoregulation is the process by which the body maintains its internal temperature within a narrow range, regardless of external conditions. The respiratory system plays a small role in thermoregulation by releasing heat through evaporation from the moist surfaces of the lungs during exhalation. When we breathe in, air is warmed and humidified within the nasal passages and upper airways. When we breathe out, this warm, moist air releases heat from the body, helping to maintain the optimal internal temperature. Additionally, increasing the respiratory rate during physical activity can help dissipate extra heat generated by muscles.
The respiratory system helps maintain blood pH by regulating the partial pressure of carbon dioxide (PCO2) in the blood. Carbon dioxide can be dissolved in the blood as bicarbonate ions (HCO3-), which act as a buffer to maintain pH levels. The chemoreceptors in the medulla oblongata and carotid and aortic bodies monitor changes in blood pH and, in response, signal the respiratory muscles to alter the respiratory rate. If blood pH drops (indicating acidosis), the respiratory rate increases to expel more carbon dioxide, raising pH. Conversely, if blood pH rises (indicating alkalosis), the respiratory rate decreases, retaining carbon dioxide, lowering pH.
Henry's law states that, at a constant temperature, the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas above the surface of the liquid. In the context of the respiratory system, this law helps explain the efficiency of gas exchange in the alveoli and capillaries. As the partial pressure of oxygen is higher in the alveolar air than in the blood, oxygen diffuses from the alveoli into the capillaries. Similarly, as the partial pressure of carbon dioxide is higher in the blood than in the alveoli, it diffuses from the capillaries into the alveoli. This ensures a continuous supply of oxygen to the body's tissues and the removal of waste products such as carbon dioxide.
