Changes in regional blood flow have not yet been explained convincingly. Risberg & Tyssebotn61 have shown that changes in myocardial output persist even after blocking the beta 1 adrenergic receptors. Savitt58 et al. have reported a decrease in coronary blood flow after blocking the autonomic nervous system.
Furthermore, the decrease in regional blood flows seems to be unrelated to the decrease in catecholamines observed in hyperoxia12'13. Thus the sympathetic nervous system does not appear to be responsible for this redistribution of cardiac output. The very fine adjustment of regional blood flows within organ systems points toward local (metabolic-related) regulation rather than global humoral or autonomic regulatory mechanisms.
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