关于动脉壁对内部压力变化的局部反应

# 关于动脉壁对内部压力变化的局部反应

# 序言

MY attention was first directed to these phenomena by the occurrence of curves like that reproduced in Fig. 1

In the course of experiments on vaso-dilator reflexes I sometimes observed what looked like a reflex of this kind, in a limb of which the nerves had been divided; the figure _reproduced shows the effect of a fall of arterial pressure produced by exciting the central end of the depressor nerve on the volume of the hind leg of the rabbit, the sciatic and the nerves accompanying the femoral artery having been cut. It will be noticed that as long as the fall of blood-pressure lasts there is a passive diminution of volume in the limb, but that as soon as the previous height of blood-pressure is attained, on cessation of the excitation, there is a consider-able expansion of the limb lasting for some time. Such a curve would usually be explained by stating that there was present all through the excitation a relaxration of the vessels, but that it was prevented from showing itself in an actual expansion of the limb by the simultaneous fall of blood-pressure; although it was able to produce such an expansion when the blood-pressure rose again owing to the vascular dilatation in other parts, chiefly splanchnic area, lasting a shorter time than in the limb. Such an explanation,obviously, will not hold here, since the leg nerves were cut, and it is plain that some other explanation must be found.

Bearing in mind the well-known reaction of muscle in general to stretching, instances of which are, amongst others, the increased force of the heart-beat produced by increased intraventricular pressure, the effect of tension on the snail's heart, and the contraction of the body walls of the earthworm in response to a pull, it is natural to suppose that the muscular coat of arteries reacts in a similar way to increased intravascular pressure; and if so, being in a state of increased tone in response to the normal blood-pressure, a lowering of that pressure will be followed by an opposite reaction, viz. a relaxation.

This is, no doubt, the explanation of the curve reproduced in Fig. 1. During the fall of blood-pressure the arteries were, in all probability,relaxed in response to that fall, but not to a sufficient extent to produce an actual increase of volume of the limb. This relaxation shows itself at once, however, when the blood-pressure returns to its original level and lasts until the muscular wall of the arteries has responded to the rise of pressure by returning to its original state of tone.

# 对压力升高的反应

In the case of the kidney vessels this reaction to increased tension is very marked, as shown in Fig. 5. All the nerves in the hilus that could be found were torn through, the vessels and ureter thoroughly painted with concentrated phenol, which I have found a very useful means of destroying the conductivity of nerve-fibres. The vessels and ureter, moreover, were tightly pinched with forceps, at the risk of causing the blood to clot, which fortunately, however, did not take place until the experiment had been performed. The kidney was enclosed in a Roy's oncometer, filled with warm physiological saline instead of oil, the fluid only reaching to the beginning of the tube leading to the piston-recorder, which contained air. The splanchnic nerve of the same side was exposed in the abdomlinal cavity and on Ludwig electrodes. The rise of blood-pressure produced by exciting the nerve is seen to cause at first a slight passive distension of the kidney, but even when the pressure is still rising the kidney begins to react by constriction which carries the piston of the recorder down to the limit of its excursion. The drum was stopped for a short time to allow the lever to return to its original position. The only source of fallacy that I can see in these experiments is the possible escape of current from the electrodes on the splanchnic nerve to the kidney vessels directly. In order to exclude this I made another experiment in which the lower end of the divided spinal cord was excited, the cord was cut at the level of the 4th thoracic nerve, and the lower end excited in the spinal canal (Fig. 6).

The kidney nerves had been cut,painted with phenol and tightly pinched with forceps. The reaction is not so striking as in Fig. 5, but there is an obvious constriction of the organ,while the blood-pressure was at its height. The circulation through the kidney was not so good in this case as in that of the previous figure,since the vessels had been pinched a longer time before the experiment was made, and had probably become partially obstructed with clot.

# 对压力下降的反应

# 在切除的动脉中的反应

It has been already pointed out above that these reactions are independent of the central nervous system, and are therefore of peripheral origin. Since no ganglia have been found in connection with the blood vessels it follows that the effects in question are of myogenic nature, as indeed one would expect from the known properties of smooth muscle. But, in view of Mac William's researches on excised arteries, it seemed worth while to attempt to obtain re- actions on them. Owing to the pressure of other work I have not been able to make many experiments of this kind. I have, however, obtained reactions, and in one case the effect was so marked as to be visible without the aid of any instrumental magnification. This case was that of a carotid artery removed from the body of a dog three hours after death by asphyxia, so that, if there were any ganglion-cells attached to the artery, they were presumably quite out of action. A cannula was inserted in one end of the artery, and the other end tied; the artery and cannula were filled with defibrinated blood and connected by india-rubber tubing to a mercury reservoir which could be raised and lowered. When now the pressure was raised inside the artery it was seen at first to swell, but immediately, and while the mercury was still kept at its height, a powerful contraction took place, in which the artery appeared to writhe like a worm. If the pressure was suddenly lowered again the artery did not return merely to the state corresponding to the lesser pressure, but underwent a considerable relaxation, which passed off just as in the vessels of the body as a whole. This reaction to lowered pressure was better seen when the artery was inclosed in a small air oncometer, consisting of a wide glass tube connected with a piston recorder, by means of which an enlarged curve of the changes of volume could be obtained. I regret that the tracing was spoilt in varnishing, so that I am unable to reproduce it here.

The fact of the occurrence of the reaction in an excised and asphyxiated artery is of importance for three reasons:--

It disposes of the objection that the phenomena in question are due to any other cause than the change of tension.
It affords a proof of their myogenic nature.
In the particular experiment described above it shows that the contraction in response to increased pressure may show itself while the pressure continues, so that the form of curve given by the kidney,which I for some time looked upon with distrust, is quite a possible one, even in the complete absence of any excitation of vaso-constrictor nerve-fibres.

上面已经指出，这些反应是独立于中枢神经系统的，因此是外周性的。由于没有发现与血管有关的神经节，因此有关的影响是肌源性的，正如人们从平滑肌的已知特性中所期望的那样。但是，鉴于麦克 - 威廉对切除的动脉所做的研究，似乎值得尝试在这些动脉上获得再作用。由于其他工作的压力，我没能做很多这样的实验。然而，我已经获得了反应，在一个案例中，效果非常明显，不需要任何仪器的放大就可以看到。这个案例是在一只犬因窒息死亡三小时后从其体内取出的颈动脉，因此，如果有任何神经节细胞附着在动脉上，它们大概已经完全失去了作用。在动脉的一端插入插管，另一端绑住；动脉和插管中充满了去纤维蛋白的血液（防止凝固），并通过印度橡胶管连接到一个可以升高和降低的水银计。此时当动脉内的压力升高时，起初看到的是肿胀，但是当水银仍保持在其原有高度时，动脉立即发生了强有力的收缩，过程中动脉似乎像蠕虫一样蠕动着。如果压力突然再次降低，动脉并不只是恢复到与较低压力相对应的状态，而是出现了相当大程度的舒张，随后这种舒张消失了，就像在整个身体的血管一样。当动脉被置于一个小型的空气器官体积测量仪中时，可以更好地看到这种对压力降低的反应，该测量仪由一根宽大的玻璃管和一个活塞记录器组成，通过它可以获得体积变化的放大曲线。遗憾的是，描记图在上漆时被破坏了，所以我无法在此复制它。

在离体动脉和窒息下动脉实际发生的反应是很重要的，原因有三：

它平息了反对意见，反对意见认为有关现象是由压力变化以外的任何其他原因造成的。
它为其肌源性提供了一个证据。
在上面描述的特殊实验中，它表明在压力持续的情况下，压力升高所对应的收缩现象在高压继续保持时可能会显示出来，因此，由肾脏给出的曲线形式，我有一段时间不相信，是相当可能的，甚至出现在完全没有任何血管收缩神经纤维的兴奋下。

# 反应的意义

It remains to indicate briefly how the behaviour of the blood vessels described in the preceding article may be of service in the normal organism.

The peripheral powers of reaction possessed by the arteries is of such a nature as to provide as far as possible for the maintenance of a constant flow of blood through the tissues supplied by them, whatever may be the height of the general blood-pressure, except in so far as they are directly overruled by impulses from the central nervous system.

As examples let us take first the case in which, say for cardiac reasons, a considerable general fall of blood-pressure is required. This,as we know, is produced by universal vascular dilatation (except in the brain); but, owing to the preponderance of the splanchnic area, the limbs, the relaxation of whose vessels is usually insufficient to produce an actual increase of their sectional area under the low arterial pressure prevailing, would be deprived of their due supply of blood when perhaps it might be particularly needed, were it not that their arterioles automatically relax to a still greater degree, and so make up for the lowered pressure by an increase of sectional area.

Take again the case in which as great as possible a rise, or fall, of arterial pressure is required; if the limb-vessels allowed themselves to be passively distended, or drained, as the case may be, the result would be to partially annul the effect of constriction, or dilatation, in the splanchnic area, but, since they react in the way described, they assist in the production of the desired end.

An especially interesting case is that of the cerebral circulation. There is, up to the present, no satisfactory evidence of the presence of a vaso-motor supply to the brain; so that when an increased blood-supply is required in that organ it is provided by constriction of vessels throughout the rest of the body, which is, in this respect, so to speak the slave of the brain. Now Hill has shown that the tendency of increased arterial distension in the brain is to produce cerebral anaemia, owing to the skull being a rigid box, so that, although the arteries may increase in size, it is at the expense of the capillaries and veins;. this swelling of the arteries is prevented by the automatic reaction of their muscular coat, as described above, so that they do not allow themselves to be distended, but become more or less rigid, and so permit the increased velocity of flow, due to increased pressure, to produce its desired effect in providing a more abundant blood-supply to the active cerebral tissue.

On the other hand it is evident that the effects of a rise of general blood-pressure of a moderate degree, produced, say, by constriction of the splanchnic area, would be to cause automatic contraction of the arteries of all other parts of the body, and thus raise still further the general blood-pressure, unless dilator impulses were sent to the vessels from the central nervous system. Thus, without the controlling government of the latter, every rise of pressure would automatically cause a further rise, and every fall, from whatever cause, a further fall of blood-pressure from peripheral vascular dilatation; i.e. a vicious circle would be established in the absence of the regulating functions of the vaso-motor centres.

我们仍需简要说明前文所述的血管行为在正常机体中是如何发挥作用的。

动脉所拥有的外周反应能力的性质是，无论总体血压多高，都能尽可能地维持血液持续流经由它们供应的组织，除非它们直接被来自中枢神经系统的冲动所支配。

作为例子，让我们先看看这样的情况，比如说由于心脏的原因，前提是总体血压下降非常明显。我们知道，这是由普遍的血管扩张产生的（脑部除外）；但是，由于内脏区域的优势，四肢的血管舒张通常不足以在那种动脉低压水平下产生实际横截面积的增加，如果不是它们的动脉血管自动舒张到更大的程度，从而通过面积的增加抵消血压下降引起的血流减少，在全身特别需要的时候，它们可能会被剥夺应有的血液供应。

再以需要尽可能大的动脉压力上升或下降的情况为例；如果肢体血管允许自己被动地膨胀或排空，视情况而定，其结果将是部分地取消收缩或扩张的影响，但是，在内脏区域，由于它们以所述方式作出反应，它们有助于产生所需的结果。

一个特别有趣的例子是脑循环的例子。到目前为止，还没有令人满意的证据表明大脑存在血管运动支配；因此，当该器官需要增加血液供应时，它是通过收缩整个身体其他部位的血管来提供的，在这方面，可以说全身血管是大脑的奴隶。现在，希尔已经证明，由于头骨是一个坚硬的盒子，因此，尽管动脉可能会增大，但它是以牺牲毛细血管和静脉为代价的，因此，大脑中动脉扩张的趋势是产生脑缺血；如上所述，动脉的这种肿胀被其外被肌肉的自动反应所阻止，因此它们不允许自己膨胀，而是或多或少地变得僵硬，因此允许由于压力升高而导致的流速增加，从而产生预期效果，为活跃的大脑组织提供更丰富的血液供应。

另一方面，已证明，适度的总体血压上升，将导致身体所有其他部位的动脉自动收缩，（例如由内脏区域的收缩产生的影响），从而进一步提高总体血压。除非中枢神经系统向血管发出舒张冲动。如果没有神经控制，每一次压力的上升都会自动导致血压进一步的上升，而每一次下降，不管是什么原因，都会导致外周血管扩张导致血压进一步下降；也就是说，如果没有血管运动中心的调节功能，就会形成一个恶性循环。

# 总结

Image from page 265 of "Elements of human physiology" (1907)

Diagram of Roy's cardiometer. On the right of the figure are the two quarter spheres which are clamped on to the pericardium at the root of the heart. itself filled with oil or air as the oncometer, and register the changes in the volume of the heart by connecting the cavity of the pericardium with some form of piston-recorder, or we may make use of Roy's cardiometer. This is a brass sphere in three segments. The two quarter spheres (Fig. 142) are applied round the base of the heart and clamped together, the cut pericardium being attached to their constricted neck, the third segment, a hemisphere, is then applied over the

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上次更新: 2022/06/06, 22:25:35

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