Respiratory responses

Respiratory responses

1. Arterial hypoxaemia

   • reduced transit time of RBCs in capillary due to high CO in athletes
   • lower TT could be shorter than time required to fully saturate Hb with 02

2. ventilatory control

   • Neural
     • Inspiratiom and expiration carried out by contraction and relaxation of respiratory muscles
     • the muscles are innervated by somatic motor neurons
     • RCC in medulla
   • central chemoreceptors
     • in medulla
     • detect pC02 or H+
   • peripheral chemoreceptors
     • aortic arch and carotid sinus
     • rterial h+ or c02
     • carotid sensitive to k+ arterial
   • afferent feedback to RCC from muscle spindles, GTO, joint receptors
   • Heavy exercise
     • alinear Ve rise and decrease in pH often simultaneous
     • rising H+ due to lactate is suggested mechanism for Ve rise
     • speculation that k+ rise increases Ve
     • rising catecholamines and temp play small role
     • neural RCC input

3. blood PCO2 PO2 K+ on ventilation

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   • Ve rise due to c02 stimulation of chemoreceptors
   • increased K+ stimulates carotid bodies > increase Ve