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 Idea is that we all seldom suffocate after 1 but we always are tossing and turning because these neurons prevent you from suffocating Not fully developed reflex in infants cannot be triggered to change position so suffocate Hyperventilation Blow off excess CO2 when you hyperventilate Makes you feel dizzy and faint Blowing off excess CO2 causes hypocapnia which triggers vasoconstriction of brain arterioles which makes the cerebrum ischemic which triggers dizziness and causes acidosis in the brain low CO2 level in the brain accumulates CO2 in the brain in the cerebral spinal fluid this stimulates the central chemoreceptors and trigger more breathing because of acidosis This ends with people passing out Usually recommended to breath in a paper bag because you are breathing in more CO2 which relieves hypocapnia and brings up CO2 levels back in the blood Kidney Function functions of kidneys o o 1 Regulation of blood pressure o 2 Involve thirst and drinking behavior o 3 All the major ions in plasma and ECF are regulated by the kidney especially Na K must be kept low HCO3 main blood buffer Ca2 ions must be kept at low level o 4 1 10 in pH is dangerous and 2 10 is fatal Does not act rapidly for change in pH but the kidney has a n unlimited capacity to excrete protons in the body needs to get rid of acid all the time o 5 Most abundant waste are nitrogenous wastes like urea and uric acid and some ammonia which are produced by metabolism and break down of amino acids Creatin is also cleared out All kinds of toxins and drugs are also excreted o 6 Produces calcitriol and EPO and activates renin which converts angiotensin to angiotensin 1 Anatomy of Urinary System o o Know that you have 2 kidneys and that they have big blood vessels going into them 20 of the cardiac output even though only a small portion of the body o The artery is very high pressure o The ureter is the tube that convey urine down the bladder o The kidney has renal pyramids has cortex and medulla o the inner most part is called the pelvis o Urine is collected in the pelvis after being in the medulla o No further modification once reaches the pelvis Cortical And Juxtamedullary Nephrons o o 2 kinds of nephrons 1 80 are confined to the cortex called cortical nephrons 2 The other ones are deeper these are called juxtamedullary nephrons have the loop of henle Blood comes from the renal artery and goes into arterioles afferent and supplies blood to the glomerulus capillaries and drains out into another arteriole efferent which feeds another capillary bed peritubular capillaries and come up again and all drains into a vein so it is like a portal system glomerular capillaries and peritubular capillaries