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Regulation of respiration

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Physiology 3120
Tom Stavraky

Human Physiology Monday, February 8, 2010 “Respiration V” Regulation of Respiration • Origin  Nerve impulses from brain  Rhythmic discharges from motor neurons that innervate respiratory muscles  Negative feedback loop  Motor neurons supplying inspiratory muscles are inhibited by those supplying the expiratory muscles  Breathing stops when spinal cord is cut above C3, 4, or 5 • Voluntary system (i.e. when swimming, holding your breath, etc.)  Pathway from cerebral cortex through corticospinal tract to the respiratory motor neurons  Limited control • Automatic system  Maintain normal blood-gas values  Very efficient  3 components 1. Receptors; also four types of receptors • Collect info on current blood-gas values; send signals to controller • Central chemoreceptors o Respond to changes in fluid around it, not the absolute concentration o Located in medulla, surrounded by brain ECF o Responds to change in PCO ;2actually an indirect response to pH (H ions don’t cross the BBB) • Peripheral chemoreceptors o In carotid bodies at bifurcation of the common carotid arteries o Respond to PO ;2when arterial PO 2ecreases below 60mmHg, get increased ventilation o Also minor response to PCO a2d pH • Lung receptors o Pulmonary stretch receptors; respond to overdistention of the lung, and slow down ventilation rate o Irritant receptors (respond to inhaled dust, cigarette smoke, etc.) • Other receptors o Not clearly defined o Receptors in nose & airways responding to chemical/mechanical strains o Joint and muscle receptors that respond during exercise o Pain & temperature receptors 2. Central controller (brain) coordinates responses to information from receptors; actually has 4 “respiratory centres” • Inspiratory area o Dorsal group of neurons in medulla o Critical in respiration o Inherent rhythmic excitability (like SA node) o
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