Download Respiration and pH, Voluntary Ventilation - Fundamentals of Physiology | BMS 360 and more Study notes Biology in PDF only on Docsity! 25 April Respiration and pH The CO2 produced in tissues is converted in RBC to carbonic acid, which dissociates to release HCO3 - and H+. Where does this acid go? Deoxyhemoglobin reversibly binds H+ and transports it. This reduces free H+, so venous blood (pH 7.36) is only slightly more acidic than arterial blood (pH 7.40) At the lungs, this reaction is reversed to produce CO2 and water. With adequate ventilation, none of the H+ from cellular respiration normally enters arterial blood Respiratory acidosis (arterial pH < 7.35): Due to hypoventilation and increased arterial pCO2 and H+ Respiratory alkalosis (arterial pH > 7.45): Due to hyperventilation and reduced arterial pCO2 and H+ Respiratory Control Localization of peripheral and center control systems that regulate ventilation The focus will be on chemoreceptors Peripheral chemoreceptors Carotid body Aortic arch Central chemoreceptors in medulla oblongata Fig 13 โ 33 Chemosensory neurons are located in the aorta (aortic bodies) and in the left and right carotid artery (carotid bodies). These sensory afferent neurons alter CNS regulation of the rate of ventilation Fig 13 โ 36 Chemoreceptors are sensitive to small changes in the carbon dioxide content of the arterial blood to change ventilation rate Figure 13 โ 34 A severe reduction in the arterial concentration of oxygen in the blood can stimulate hyperventilation Carotid and Aortic Arch Chemoreceptors The glomus cells are the chemoreceptors (located near the baroreceptors) They increase rate and depth of ventilation in response to arterial Increase in pCO2. This is the primary stimulus, and helps match ventilation to CO2 production Decrease in pH (acidosis) Decrease in pO2 (requires large drop to <60 โ 70 mm Hg; COPD; elevations > 3,000 m or 10,000 feet) Carotid and aortic arch chemoreceptors when pO2 < 60 โ 70 mm Hg Low pO2 K+ channels close Cell depolarizes Voltage gated Ca2+ channel opens Ca2+ entry Exocytosis of dopamine-containing vesicles Signal to medullary centers to increase ventilation Figure 13 โ 35
