Spectral Characteristics of Spontaneous Oscillations in Cerebral Haemodynamics are Posture Dependent
Autonomic reflexes are responsible for adjusting the cardiovascular system in response to gravitational displacement of blood during changes in posture1. In human physiology, a posture change from supine to standing results in venous pooling in the lower limbs and pelvic area (equivalent to the loss of 500m1 of blood from the systemic circulation) and an increased filtration from capillaries into interstitial space2. In turn, these effects cause a transient dip in effective circulating blood volume and potentially a small reduction in cerebral and peripheral oxygen delivery. This effect is not prolonged in a healthy individual since the decrease in arterial pressure triggers an immediate response from the baroreceptor-mediated sympathetic mechanisms.
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