Document Detail


Reflex control of the circulation during exercise: chemoreflexes and mechanoreflexes.
MedLine Citation:
PMID:  2228848     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The overall scheme for control is as follows: central command sets basic patterns of cardiovascular effector activity, which is modulated via muscle chemo- and mechanoreflexes and arterial mechanoreflexes (baroreflexes) as appropriate error signals develop. A key question is whether the primary error corrected is a mismatch between blood flow and metabolism (a flow error that accumulates muscle metabolites that activate group III and IV chemosensitive muscle afferents) or a mismatch between cardiac output (CO) and vascular conductance [a blood pressure (BP) error] that activates the arterial baroreflex and raises BP. Reduction in muscle blood flow to a threshold for the muscle chemoreflex raises muscle metabolite concentration and reflexly raises BP by activating chemosensitive muscle afferents. In isometric exercise, sympathetic nervous activity (SNA) is increased mainly by muscle chemoreflex whereas central command raises heart rate (HR) and CO by vagal withdrawal. Cardiovascular control changes for dynamic exercise with large muscles. At exercise onset, central command increases HR by vagal withdrawal and "resets" the baroreflex to a higher BP. As long as vagal withdrawal can raise HR and CO rapidly so that BP rises quickly to its higher operating point, there is no mismatch between CO and vascular conductance (no BP error) and SNA does not increase. Increased SNA occurs at whatever HR (depending on species) exceeds the range of vagal withdrawal; the additional sympathetically mediated rise in CO needed to raise BP to its new operating point is slower and leads to a BP error. Sympathetic vasoconstriction is needed to complete the rise in BP. The baroreflex is essential for BP elevation at onset of exercise and for BP stabilization during mild exercise (subthreshold for chemoreflex), and it can oppose or magnify the chemoreflex when it is activated at higher work rates. Ultimately, when vascular conductance exceeds cardiac pumping capacity in the most severe exercise both chemoreflex and baroreflex must maintain BP by vasoconstricting active muscle.
Authors:
L B Rowell; D S O'Leary
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.; Review    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  69     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1990 Aug 
Date Detail:
Created Date:  1990-12-05     Completed Date:  1990-12-05     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  407-18     Citation Subset:  IM; S    
Affiliation:
Department of Physiology and Biophysics, University of Washington, School of Medicine, Seattle 98195.
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MeSH Terms
Descriptor/Qualifier:
Animals
Chemoreceptor Cells / physiology
Exercise / physiology*
Hemodynamics / physiology
Humans
Mechanoreceptors / physiology
Muscles / blood supply,  innervation,  physiology
Physical Exertion / physiology
Reflex / physiology*
Sympathetic Nervous System / physiology
Grant Support
ID/Acronym/Agency:
HL-07803/HL/NHLBI NIH HHS; HL-16910/HL/NHLBI NIH HHS

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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