EHS 385 Lecture Notes - Lecture 23: Bloodborne, Catecholamine, Homeostasis
9 Dec 2017
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During prolonged submax exercise in hot/humid environment: ventilation tends to drift upward, increased blood temp affects respiratory control center, little change in pco2, higher ventilation not due to increased pco2. Ventilation (ve: linear increase up to 50-75% vo2max, exponential increase beyond this point, ventilatory threshold (tvent): breakpoint at which ve increases exponentially during exercise. Po2: maintained w/in 10-12 mmhf of resting value. Ventilation (ve): tvent occurs at higher % vo2max compared to untrained subjects. Expiration: occurs when diaphragm relaxes due to passive recoil of lungs and chest wall. Respiratory muscle drive is controlled by somatic motor neurons (motor neurons related to voluntary movements) in spinal cord: somatic motor neuron activity controlled by respiratory control center, located in medulla oblongata and pons areas in brain stem. Stimulus for inspiration comes from four respiratory rhythm-generating centers located in brain stem: in medulla oblongata: prebotzinger complex and retrotrapezoidal nucleus, in pons: pneumotaxic center and caudal pons.
