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Biology 22 The Respiratory system

Terms in this set (40)

-Higher brain center: Through hypothalamic controls, an increased body temperature will cause an increase in respiratory rate. A student cold shock will have the opposite effect (if you fall through the ice into cold water, our breathing will stop) Strong emotions also affect breathing. You also have voluntary control of breathing, although these will be overridden if blood carbon dioxide levels reach levels that stimulate reflexive breathing.
-Chemical factors: Chemical control of breathing is mediated primarily via a feedback mechanism arising from stimulation of the central and peripheral chemoreceptors. (1) Central Chemoreceptors: These are located in the medulla and are primarily influenced by the pH of the cerebro spinal fluid (CSF), and interstitial fluid of the brainstem. CSF does not contain the protein hydrogen buffers found in blood, therefore and increase in partial pressure of carbon dioxide (PCO2) causes and increase in hydrogen ion concentration, The central chemoreceptors are then stimulated to increase the rate and depth of breathing to get rid of the carbon dioxide (CO2) thereby bringing the pH back towards normal. Should the opposite occur and the hydrogen ion concentration of the CSF is low the chemoreceptors send a message to decrease the rate and depth of respiration, thereby retaining CO2 and bringing the pH towards normal. Chemoreceptors do not respond to devreases in the partial pressure of oxygen (PO2)
(2) Peripheral Chemoreceptors: Include the carotid and aortic bodies. They are primarily stimulated by an increased PCO2 or an increase in hydrogen ion concentration (pH), but are less sensitive to these changes than are the central chemoreceptors. The peripheral chemoreceptors are also sensitive to the PaO2 of blood. Hypoxaemia will lead to an increased rate and depth of breathing. With chronic hypoxaemia the stimulation of these receptors becomes depressed.