Human Physiology - William F. Ganong 2002

Blood Circulation
Regulation of the Cardiovascular System
Introduction

In humans and mammals, numerous mechanisms regulate The Cardiovascular system to enhance Blood supply to active Tissues and increase or decrease heat dissipation through blood redistribution. In pathological states, such as Hemorrhage, these regulatory mechanisms sustain Blood Circulation in The Heart and Brain. Under particularly critical conditions, blood flow to vital Organs is prioritized at the expense of other tissues.

Circulatory adjustments occur via changes in Cardiac Output, alterations in the diameter of resistance vessels (primarily arterioles), or variations in the volume of blood pooled in capacitance vessels (Veins). The REGULATION OF CARDIAC output is detailed in Chapter 29. Arteriolar diameter is modulated, in part, through autoregulation. In highly active tissues, arteriolar diameter increases in response to locally produced vasodilators, and is further modified by Endothelium-Derived Factors. Systemic regulation is mediated by circulating vasoactive substances and the nerves innervating the arterioles. The diameter of capacitance vessels is likewise altered by blood-borne vasoactive substances and vasomotor nerves. Together, systemic and local mechanisms govern overall blood circulation throughout the body.

Typically, the terms vasoconstriction and vasodilation refer to the constriction and dilation of resistance vessels. Changes in venous diameter are designated as venoconstriction and venodilation.



Last update: 10/08/2026

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