Respiratory System and Kidney Function

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Respiratory System and Kidney Function

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 35 Current Lecture  Regulation of Ventilation o o The ventilating muscles are skeletal muscles and are not spontaneously active but innervated by alpha motor neurons o These are spinal motor neurons going to the respiratory muscle o In the brainstem there are 2 groups of nerve cells called the dorsal and ventral respiratory groups where the rhythms that run the respiratory system originate. Exert these APs in bursts o This goes to the spinal and brainstem motor neurons that innervate these muscles o The control of this outflow is determined by the level of the respiratory gases o Oxygen does not play a major role in quiet breathing but rather CO2 plays a bigger role o CO2 is a direct waste product of metabolism and directly indicates the need for respiration o Gas sensitive nerves: chemoreceptors which are reflexes that will sense the levels of respiratory levels  1. Central chemoreceptors  In the brainstem  Sense respiratory gases  Sensitive to CO2  Are involved in moment to moment regulation of rate and depth of breathing  The neurons in the central chemorecpetors are not actually CO2 sensitive but H+ ion sensitive- get excited by low pH and stimulate respiration  Protons cannot cross the blood brain barrier- but CO2 readily diffuses through- CO2 diffuses out of the blood when it is high (when metabolism exceeds respiration) and the acidification of the CSF will be what the neurons sense and respond to  Slight changes in pH is what determines the need for respiration  2. Peripheral chemoreceptors  In aortic body and carotid body  Measure the oxygen levels in systemic circulation  Called glomus cells (like hair cells-don’t have axons) and they sense oxygen and in response to hypoxia (low O2) they release dopamine as a NT and this excites afferent sensory nerves which signals to the respiratory control groups to stimulate respiration  Usually not very active- only in severe hypoxia  May come into play during high altitudes  Come into play in COPD where hypoxia can occur  There are also reflexes that trigger coughing and sneezing, vocalization, herring breuer reflex (protective when exercise, breath more deeply and rapidly, at the point where the tidal volume reaches about twice normal (1L) then this reflex protects the lungs from overinflating by inhibiting the respiratory – cannot hold breath to commit suicide because of these reflexes (brain hypoxia will make you pass out)  SIDS  Sudden infant death syndrome  A form of sleep apnea  Leading cause of death in babies under 1 in the US  Prevent nose and mouth from being obstructed by loose stuff  Resulted in a lot of misshapen heads (get flat in the back)  Deficiency in serotonin in the brainstem- usually a lot of serotonin containing neurons around the respiratory neurons  Appears that serotonin is important in arousal and waking up during sleep  Mechanism not really understood

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