Stimulating the vagus nerve fish shock different frequencies and power, you can call reflex decrease or increase of vascular tone and accordingly the increase or decrease of the heartbeat. Let's remind, that species heart is not sympathetic innervation, "specific accelerator". Such experiments repeatedly performed by us and other students Meters, Udalova. But this is not enough. The focus of sensitive nerve endings fish - its gills. Here too can be caused by reflexes of opposite signs. Reflexes with gills absolutely necessary for the fish: the full release of blood does not kill fish, but the anesthesia gills novocaine causes death. This is understandable: in the field of gills there is a contact between the internal and external environment, and hence are the most important signals.
Now invite armed with the knowledge of the reader to participate in our great long-term study of regulation of vessels with those positions, which is clear from the previous chapters, that is, with the joint positions of schools Chernihiv and Udalova. Details will dosagem along the way.
Let's start with frogs. We remember that in experiments Chernihiv irritation heart of chemoreceptors nicotine lowered blood pressure (vascular tone), and off receptors of the heart novocaine increase it. These experiments Century N. put on rabbits. It is expected that the reflexes participated mainly chemoreceptors.
Let's see how vessels react to the signals of chemoreceptors and mechanoreceptors. Let's start with the last. For this heart to isolate from the vascular system, which will perfusionist under constant pressure. The perfusion solution is included in the aorta and out drops from the abdominal veins, the number of drops per minute - an indicator of vascular tone, "integral" tone. The pressure in the ventricle will change under the control of water gauge. Emphasize that the heart stores with body only nervous connection, and if kaplavas change frequency recorded drops, then this is the reflex of the heart, vessels through vasomotor center. Ventricular pressure - 2 mm of a water column; the outflow does not change. Four millimeters - outflow almost doubled. Six - outflow, i.e. vascular tone, again equal to the original. A further increase in pressure in the heart leads to rising tone: the outflow falls under pressure from 8 to 50 mm of a water column and if to increase the pressure, the tone is reduced up to intracardiac pressure 250 mm of a water column and reaches approximately the same value that was at the lowest point of the curve is under pressure 4 mm of a water column.
And suddenly it's not a reflex? Get accurate evidence: will destroy the vasomotor center, cut Vagony, simpaticos - in any of these cases, all the answers vessels on pressure changes in heart disappear.
Let us now study chemoreceptors frog's heart. To do this, take a standard-size piece of blotter, soaked in a solution of nicotine. In the first experiment on the surface of the heart, put a piece of paper with a saline solution, to make sure that the paper is not a significant stimulus. No, it is not: the pressure has not changed. Now let's try a solution of nicotine in the increasing of concentration. Let's start with the breeding in a hundred billion times. To impregnate this liquid square of filter paper will last quarter drops of solution - hundredth of a cubic centimeter; on receptors will get only a small part of what impregnated paper - no more than one tenth part. But if work even the tenth part, it will be 1 year, divided by the unit with sixteen zero - receptors of the heart common frogs react to this dose, and the blood pressure goes down. (By the way, what kind of cigarettes do you like more?)

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