The functional tasks of the activity of the mechanism regulating the cerebral circulation

• Published in: Fiziologicheskii zhurnal SSSR imeni I. M. Sechenova Vol. 77; no. 9; p. 55
• Main Author: Moskalenko, Iu E
• Format: Journal Article
• Language: Russian
• Published: Russia (Federation) 01-09-1991
• Subjects: Animals; Brain - blood supply; Brain - metabolism; Brain Diseases - physiopathology; Carbon Dioxide - metabolism; Cerebrovascular Circulation - physiology; Humans; Hyperemia - physiopathology; Methods; Nerve Tissue - physiology; Rabbits; Water-Electrolyte Balance - physiology
• ISSN: 0015-329X

Modern experimental and clinical data suggest that physiological mechanism, responsible for maintaining adequate brain blood supply under different conditions has a complex functional task, which besides sufficient metabolic transport to brain tissue, consists in supporting of water balance of brain tissue and evacuation of wastes. These functions realize by synergistic acting of several control links--neurogenic, metabolic, myogenic and humoral, every one of them has its own channel of input information and feedback. Physiological reactions of cerebrovascular system to adequate sensory activation have a task, first of all, to support of metabolic supply of nerve tissue. Therefore, after the beginning of sensory activation, oxygen availability in brain tissue is significantly increase, but at the same time some changes of hydratation nerve tissue is taking place. The last is possible to observe by analysis of changes in amplitude and configuration of electrical impedance pulsations, recording from brain implanted electrodes. These changes of hydratation of nerve tissue is observing during short time period and then is compensating. During during neuronal activation the concentration of wastes in brain tissue is slightly increase, which reflects in changes of brain tissue pH and pCO2. However, in situations, closed to extreme ones, a some hierarchic relationships between particular functional tasks of cerebrovascular control mechanism are observed. (1) Under arterial hypertension, when it is impossible to maintain at the same time both metabolic supply of brain tissue and to support water balance of nerve tissue, experimental and clinical data indicates, that the leader place take processes, responsible for the hydration of nerve tissue. So, the same decrease of cerebral blood flow during arterial hypertension indicates, that the action of control mechanism of cerebral circulatory system directed to minimization of a risk of developing of brain edema. (2) In cases of arterial hypotension, which accompanying by chronic cerebral circulatory insufficiency, the main functional task of cerebrovascular control mechanism becomes to direct to evacuation of wastes, because they are slowly collecting in brain tissue, although the metabolic supply of brain tissue is often in sufficient limits. In such conditions vasodilator drugs with a short time period of action (30-40 min.) have a comparative long (3-5 hours) positive effect for patients. During time period of increased brain blood flow, washing out of brain tissue from wastes is taking place. Generally, the first of mentioned processes is forming the left and the second--right parts of the curve, which represents the autoregulator phenomenon.