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REFLEXLY EVOKED COACTIVATION OF CARDIAC VAGAL AND SYMPATHETIC MOTOR OUTFLOWS: OBSERVATIONS AND FUNCTIONAL IMPLICATIONS
Author(s) -
Paton Julian FR,
Nalivaiko Eugene,
Boscan Pedro,
Pickering Anthony E
Publication year - 2006
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2006.04518.x
Subject(s) - microneurography , bradycardia , reflex , medicine , heart rate , reflex bradycardia , chemoreceptor , peripheral , nociceptor , baroreceptor , anesthesia , coactivation , autonomic nervous system , cardiology , baroreflex , electromyography , nociception , blood pressure , physical medicine and rehabilitation , receptor
SUMMARY1 The purpose of the present review is to highlight the pattern of activity in the parasympathetic and sympathetic nerves innervating the heart during their reflex activation. 2 We describe the well‐known reciprocal control of cardiac vagal and sympathetic activity during the baroreceptor reflex, but point out that this appears to be the exception rather than the rule and that many other reflexes reviewed herein (e.g. peripheral chemoreceptor, nociceptor, diving response and oculocardiac) involve simultaneous coactivation of both autonomic limbs. 3 The heart rate response during simultaneous activation of cardiac autonomic outflows is unpredictable because it does not simply reflect the summation of opposing influences. Indeed, it can result in bradycardia (peripheral chemoreceptor, diving and corneal), tachycardia (nociceptor) and, in some circumstances, can predispose to malignant arrhythmias. 4 We propose that this cardiac autonomic coactivation may allow greater cardiac output during bradycardia (increased ventricular filling time and stronger contraction) than activation of the sympathetic limb alone. This may be important when pumping blood into a constricted vascular tree, such as is the case during the peripheral chemoreceptor reflex and the diving response.