We planet Earth

We often hear speculative considerations about that in orthostatic reactions circulatory play a significant role subcortical structures themselves. Irritation of the rear Department of the hypothalamus are really able to activate centrifugal sympathetic nerves vessels, but in this case the role of the posterior hypothalamus hardly significant, because when you turn off the chemoreceptors, the keepers of the homeostasis of the intercellular medium brain and located on the anterolateral the surface of the medulla oblongata, the outflow of interstitial fluid and blood from the whole brain irritation hypothalamic structures shock, do not cause any vascular responses. Another matter of tissue receptors of the entire body and have just mentioned chemoreceptor zone oblong brain: if irritation always happen powerful vascular reactions, depending, as usual, on the strength of irritation. In this situation, when mechanoreceptors reflex safely keeps blood pressure near norms and chemoreceptors come into a state of more and more excitement, i.e. after 10 with orthostasis, the further course of events slowed down, the position for some time almost stabilized.
The accumulation of acid metabolites tissue chemoreceptors imposerait deeper and finally fill in the deficit of the centripetal information, which arose due to low pressure in the aorta heart and carotid sinus. Recall that tissue chemoreceptor whose sensitive terminal immersed in the intercellular fluid any fabric, excited oxidized metabolites containing hydrogen ion. Specialized chemoreceptors carotid and aortic pomozov respond to reduced oxygen levels in the blood. Finally, chemoreceptors anterolateral surface of the medulla oblongata excited hydrogen ions and high content of carbonic acid in venous blood and interstitial fluid that drains from the brain. The status quo is that all three species of chemoreceptors there is a reason strenuously to indicate the alarm condition of the body, and this applies in particular to receptors on the surface of the medulla oblongata. Let us explain.
In the body circulates too little blood, and it flows too slowly to compensate for the lack of its volume. Therefore, the oxygen content in it is not enough. On the contrary, oxygen starvation of all organs and tissues leads to the acidification of the blood and lymph, excess hydrogen ions, stimulation of tissue receptors. The brain receives blood with low oxygen content and is inadequate, but with increased content of hydrogen ions. High voltage carbon dioxide in the blood is not lifted within one cycle through the pulmonary circulation, and from such-and-such blood brain properly vycerpanie all required him oxygen. At the exit of the brain Vienna and intercellular fluid are particularly high concentration of carbon dioxide and therefore hydrogen ions.
All this at first leads to strengthen the "segmentarity" vascular tone, but only up to a certain limit. There comes a moment when the power centripetal activity chemoreceptor origin exceeds the shortage of pulses from mechanoreceptors, and then it happens failure: sympathetic impulses to receptacles, coming from vasomotor centers, begins to wane. In the vascular tone, reaching in the beginning of the study, almost supernatural values, reduced. At the same time decreases the frequency of cardiac contractions. Decreases blood pressure. The brain (located at the top!) remains without blood, without oxygen - he was off like a light bulb without current. Breathing slows or stops. The next phase - loss of consciousness.
In actual fact, the mind is not lost, because already started to decrease heart rate, blood pressure reduction and weakening of the respiratory shows that it is time to stop the study.

Pages: 1 2 3 4 5 6 7