Portland State University. Department of Biology.
Stanley S. Hillman
Date of Publication
Master of Science (M.S.) in Biology
Baroreceptors, Blood pressure -- Regulation, Toads -- Physiology, Amphibians -- Physiology
1 online resource (v, 42 p.)
The present study documents that baroreceptors located in the pulmocutaneous artery (PCA) are key components in control of lymph heart rate in amphibians. A negative feedback control loop exists between arterial pressure and lymphatic heart rate. The recurrent laryngeal nerve (rLN), which innervates the PCA baroreceptors, transmits information on arterial pressure to integration centers in the central nervous system. Lymphatic heart rate (LHR) is reduced as a result of increases in arterial pressure. This loop was determined using three experimental protocols. First, the correlation between LHR reduction and hormonally induced vasoconstriction was determined. Increases in arterial pressure due to pressor actions of angiotensin II and arginine vasotocin at high concentrations was negatively correlated to LHR. Second, lymphatic heart rate changes due to natural increases in arterial pressure were compared to rate changes due to increase in arterial pressure after bilateral denervation of the rLN. Post-denervation LHR was not affected by natural increase in arterial pressure prior to the establishment of a new resting arterial pressure. Increase in arterial pressure due to administration of vasoconstricting hormones was negatively correlated with LHR following denervation. Third, the effect on LHR due to direct stimulation of the rLN was studied. Stimulation of the rLN caused LHR to stop without increases in arterial pressure. Presumably, this negative feedback loop is present to limit fluid return to the cardiovascular system from the lymphatic system during periods of acute hypertension. Reduction in the return of lymph volume to the cardiovascular system could eliminate potential damage to pulmonary tissues due to high arterial pressures.
Crossley II, Dane Alan, "The Role of Pulmocutaneous Baroreceptors in the Control of Lymphatic Heart Rate in the Toad Bufo Marinus" (1995). Dissertations and Theses. Paper 4892.