Therapeutics of the circulation / by Sir Lauder Brunton.

  • Lauder Brunton
Date:
1914
Catalogue details

Licence: Public Domain Mark

Credit: Therapeutics of the circulation / by Sir Lauder Brunton. Source: Wellcome Collection.

    45/568 page 17
    arterioles were dilated and the heart did not beat more actively, so as to supply a larger amount of blood, the arteries would become so empty and the pressure in them so low that the circulation through the various organs would be insufficient to maintain their functional activity; and the brain, being especially sensitive, syncope would result. Co-ordination of Heart’s Action and Blood- pressure. Centres in Medulla Oblongata.— Co-ordination is maintained by means of the nervous system, the chief centre of which is in the medulla oblongata, where the most import¬ ant part of the vaso-motor centre is located, and where also the vagus roots are situated. By irritation (a) of the vagus roots, or (J?) of their trunks, or (c) of their ends in the heart, the movements of the heart become slower and often weaker; although the slowing and weak¬ ness may occur more or less independently of each other. Any excessive tension in the vessels, involving as it does the blood-supply of the medulla, acts as an irritant to the vagus centre, puts the vagus nerve into action, slows the heart, and thus prevents the tension from rising too high.* On the other hand, diminished pressure in the arterial system lessens the normal stimulation of the vagus centre, so that the vagus nerves act less powerfully on the * Francois Franck (Traveaux du laboratoire de Marey, 1877, vol. iii., p. 276) has shown this in a brain kept alive by artificial circulation and separated from the rest of the body, except that the vagi remained intact, so that the brain could act on the heart.
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