- Title
- Some mechanisms of reflex control of the circulation by the sympatho-adrenal system
- Creator
- Korner, Paul I.; Chalmers, John P.; White, Saxon William
- Relation
- Circulation Research Vol. 21, Issue 6, p. 157-172
- Relation
- http://pt02.wkhealth.com/pt/re/aha/abstract.00003012-196712001-00017.htm
- Publisher
- Lippincott Williams & Wilkins
- Resource Type
- journal article
- Date
- 1967
- Description
- The effects of severe arterial hypoxia (breathing low 0₂ mixtures), and primary tissue hypoxia (breathing 0.2% CO + 21% 0₂) with normal arterial Po₂, on the sympatho-adrenal (S-A) activity, have been studied in unanesthetized rabbits. In arterial hypoxia the chemoreceptors are the primary source of reflex activity, whereas this increases through baroreceptor reflexes in primary tissue hypoxia. In arterial hypoxia total S-A discharge increases markedly, and there is preponderance of sympathetic nerve activity over adrenal medullary hormone secretion. In primary tissue hypoxia total S-A discharge is smaller, and activity of both S-A components is balanced more evenly. Changes in peripheral blood flow (portal vein, renal vein, muscle, ear, and hindlimb skin) observed in normal animals differ in the two types of hypoxia, and the flow changes in each type in the various beds are not uniform. The differences between the two types of hypoxia are greatly reduced in "de-efferented" animals without autonomic effectors, suggesting a similarity of local dilator effects on a given bed. The experiments suggest that the nonuniform blood-flow patterns seen in normal animals after strong stimulation of a specific receptor occur despite a diffusely acting neural discharge on most vascular beds controlled by the S-A system. Stimulation of different receptors varies the total S-A discharge, and the proportion of neural relative to adrenal activity. Despite the generalized S-A discharge produced by stimulating one receptor, nonuniform blood-flow patterns are produced, as a result of differences in the mode of action on the various beds of the adrenal hormones acting as peripheral inhibitory or excitatory modulators of sympathetic nerve activity and because of differences in local factors. The ear skin blood-flow responses are an exception to the hypothesis of a diffusely acting generalized S-A discharge, since in this region (and to a lesser extent in the body skin) with a special thermoregulatory function, the direction of change in sympathetic nerve discharge diverges from that of the other vascular beds.
- Subject
- arterial hypoxia; chemoreceptors; primary tissue hypoxia; carboxyhemoglobinemia; baroreceptors; cardiac output; peripheral blood flow; 'steady-state' analysis; transient analysis
- Identifier
- http://hdl.handle.net/1959.13/938888
- Identifier
- uon:12690
- Identifier
- ISSN:0009-7330
- Language
- eng
- Full Text
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