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(河南省李广明问) 要了解和回答这个问题,首先应了解一下脑血管的自身调节作用。正常人血压的升高并不改变脑血流量,因为脑血流量与血压及血管阻力之间存在着如下的关系:脑血流量=血压/脑血管阻力血压升高时则促进脑血管收缩,脑血管阻力升高;血压降低时则引起血管扩张,阻力降低;故全身血压虽有波动,脑血流量却可保持恒定不变。脑小动脉对血压改变的这种舒缩反应的能力就是脑血管的自身调节作用,这是一种很重要的保护机制。脑血管的这种自身调节机能在很大的血压范围内均可生效,只有当平均动脉压低于下限(60～70毫米汞柱)或超过上限(160毫米汞柱)时,脑小动脉的这种调节机能才
(Henan Province, Li Guangming asked) To understand and answer this question, we should first understand the role of cerebrovascular self-regulation. Normal blood pressure does not change the cerebral blood flow, cerebral blood flow and blood pressure and vascular resistance exists between the following relationship: Cerebral blood flow = blood pressure / cerebral vascular resistance when blood pressure is increased when cerebral vasoconstriction, brain Vascular resistance increased; blood pressure is caused by vasodilation, decreased resistance; so systemic blood pressure fluctuations, cerebral blood flow can be maintained constant. The ability of the arterioles to respond to changes in blood pressure as a result of their own regulation of the blood vessels is an important protective mechanism. This self-regulating function of cerebrovascular can be effective over a wide range of blood pressures, and only when the mean arterial pressure is below the lower limit (60-70 mmHg) or above the upper limit (160 mmHg) The kind of regulation function before