Mechanism of respiration, pulmonary ventilation, transport oxygen and carbon dioxide in blood and control of respiration?

The mechanism of respiration involves several processes that work together to ensure the exchange of oxygen and carbon dioxide in the body. These processes include pulmonary ventilation, transport of oxygen and carbon dioxide in the blood, and the control of respiration.

1. Pulmonary Ventilation: This process involves the movement of air in and out of the lungs. It is achieved through the contraction and relaxation of the diaphragm and intercostal muscles. During inhalation, the diaphragm contracts and moves downward, while the intercostal muscles contract, causing the ribcage to expand. This increases the volume of the thoracic cavity, leading to a decrease in pressure, and air rushes into the lungs. During exhalation, the diaphragm and intercostal muscles relax, causing the thoracic cavity to decrease in volume, which increases the pressure, and air is expelled from the lungs.

2. Transport of Oxygen and Carbon Dioxide in Blood: Oxygen is transported in the blood primarily by binding to hemoglobin molecules in red blood cells. Oxygen diffuses from the alveoli in the lungs into the capillaries surrounding them, where it binds to hemoglobin. The oxygenated blood is then transported to the body tissues, where oxygen is released from hemoglobin and diffuses into the cells for cellular respiration. Carbon dioxide, produced as a waste product of cellular respiration, diffuses into the capillaries and is transported in the blood in three forms: dissolved in plasma, bound to hemoglobin, or as bicarbonate ions. In the lungs, carbon dioxide is released from the blood and expelled during exhalation.

3. Control of Respiration: The control of respiration is regulated by the respiratory centers located in the brainstem. The primary respiratory center is the medulla oblongata, which contains the inspiratory and expiratory centers. These centers receive input from chemoreceptors that monitor the levels of oxygen, carbon dioxide, and pH in the blood. When the levels of carbon dioxide increase or the pH decreases (indicating a buildup of carbon dioxide), the respiratory centers are stimulated to increase the rate and depth of breathing. Conversely, when the levels of carbon dioxide decrease or the pH increases, the respiratory centers are inhibited, leading to a decrease in breathing rate and depth. Additionally, the respiratory centers receive input from other areas of the brain, such as the cerebral cortex, which can voluntarily control breathing, for example, during speaking or holding one's breath.