BIOM1060 Lecture Notes - Lecture 28: Metabolic Acidosis, Oxygen Therapy, Cerebral Cortex
BIOM1060 18/04/18
CONTROL OF RESPIRATION
Control centres for respiration in brain stem
- Rostral ventromedial medulla: pacemaking activity (cells constantly depolarise until reach
threshold and make pacemaking potential)
- Dorsal respiratory group: innervates diaphragm in quiet breathing (only connected to
inspiratory nerves)
- Ventral respiratory group: innervates muscles during increased/active breathing
(connected to both inspiratory and expiratory nerves)
- Central chemoreceptors: monitor pH of brain’s extracellular fluid (located near dorsal
and ventral groups)
oIn presence of carbonic anhydrase enzyme and water, CO2 forms carbonic
acid which dissociates into hydrogen and bicarbonate ions - changes pH of
extracellular fluid
oIf pH drops, strongly signals medullary respiratory centre to increase
ventilation (indirectly monitor partial pressure of CO2)
- Peripheral chemoreceptors: monitor PO2 and pH (located in aortic and carotid bodies)
oPO2: hypoxic drive to breathe (signal medullary respiratory centre to increase
ventilation if arterial PO2 < 60mm Hg)
opH: increased CO2 = more acidic (signal for increase in ventilation if pH falls)
Sever lung disease and chronic elevated arterial PCO2
- Increased CO2 = increased carbon dioxide-induced H+ ions = decreased pH (more acidic)
- Renal compensation of respiratory acidosis: kidneys start to retain bicarbonate (do not
excrete extra bicarbonate ions into urine but instead into blood)
oIncreased bicarbonate in blood = buffer excess hydrogen ions = normalises
pH
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Document Summary
Rostral ventromedial medulla: pacemaking activity (cells constantly depolarise until reach threshold and make pacemaking potential) Dorsal respiratory group: innervates diaphragm in quiet breathing (only connected to inspiratory nerves) Ventral respiratory group: innervates muscles during increased/active breathing (connected to both inspiratory and expiratory nerves) Central chemoreceptors: monitor ph of brain"s extracellular fluid (located near dorsal and ventral groups) o. In presence of carbonic anhydrase enzyme and water, co2 forms carbonic acid which dissociates into hydrogen and bicarbonate ions - changes ph of extracellular fluid o. If ph drops, strongly signals medullary respiratory centre to increase ventilation (indirectly monitor partial pressure of co2) Peripheral chemoreceptors: monitor po2 and ph (located in aortic and carotid bodies) o. Po2: hypoxic drive to breathe (signal medullary respiratory centre to increase ventilation if arterial po2 < 60mm hg) o ph: increased co2 = more acidic (signal for increase in ventilation if ph falls) Sever lung disease and chronic elevated arterial pco2.
