Integrated human physiology: breathing, blood pressure and blood flow to the brain.

摘要

The cerebral vasculature rapidly adapts to changes in perfusion pressure (cerebral autoregulation), regional metabolic requirements of the brain (neurovascular coupling), autonomic neural activity, and humoral factors (cerebrovascular reactivity). Regulation of cerebral blood flow (CBF) is therefore highly controlled and involves a wide spectrum of regulatory mechanisms that together work to maintain optimum oxygen and nutrient supply. It is well-established that the cerebral vasculature is highly sensitive to changes in arterial blood gases, in particular the partial pressure of arterial carbon dioxide (P_(aCO_2))- The teleological relevance of this unique feature of the brain is likely to lie in the need to tightly control brain pH and its related impact on ventilatory control at the level of the central chemo-receptors. Changes in arterial blood gases, in particular those that cause hypoxaemia and hypercapnia, also lead to widespread effects on the systemic vasculature often leading to sympathoexcitation and related blood pressure (BP) elevations via vasoconstriction (Ainslie et al. 2005).