Changes in the baroreceptor reflex at the start of muscle contraction in the decerebrate cat.

McWilliam, P. N.; Yang, T. F.; Chen, L X

doi:10.1113/jphysiol.1991.sp018566

Cited by 43 publications

(44 citation statements)

References 19 publications

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“…One known mechanism responsible for this baroreflex resetting during exercise is the feedback from skeletal muscle afferents. In animal and human studies, it has been shown that neural feedback from the skeletal muscles modulates the arterial baroreflex function (19,28,46). Employing the HR-SBRS technique to study the interaction between these two reflexes, our group recently observed that during mild and moderate dynamic exercise, MMA causes not only resetting of the arterial baroreflex but also a decrease in HR-SBRS (40).…”

Section: Discussionmentioning

confidence: 96%

Progressive muscle metaboreflex activation gradually decreases spontaneous heart rate baroreflex sensitivity during dynamic exercise

Sala‐Mercado

Ichinose

Coutsos³

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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Ischemia of active skeletal muscle elicits a pressor response termed the muscle metaboreflex. We tested the hypothesis that in normal dogs during dynamic exercise, graded muscle metaboreflex activation (MMA) would progressively attenuate spontaneous heart rate baroreflex sensitivity (SBRS). The animals were chronically instrumented to measure heart rate (HR), cardiac output (CO), mean and systolic arterial pressure (MAP and SAP), and left ventricular systolic pressures (LVSP) at rest and during mild or moderate treadmill exercise before and during progressive MMA [via graded reductions of hindlimb blood flow (HLBF)]. SBRS [slopes of the linear relationships (LRs) between HR and LVSP or SAP during spontaneous sequences of > or =3 consecutive beats when HR changed inversely vs. pressure] decreased during mild exercise from the resting values (-5.56 +/- 0.86 vs. -2.67 +/- 0.50 beats.min(-1).mmHg(-1), P <0.05), and in addition, these LRs were shifted upward. Progressive MMA gradually and linearly increased MAP, CO, and HR; linearly decreased SBRS; and shifted LRs upward and rightward to higher HR and pressures denoting baroreflex resetting. Moderate exercise caused a substantial reduction in SBRS (-1.57 +/- 0.38 beats.min(-1).mmHg(-1), P <0.05) and both an upward and rightward resetting. Gradual MMA at this higher workload also caused significant progressive increases in MAP, CO, and HR and progressive decreases in SBRS, and the LRs were shifted to higher MAP and HR. Our results demonstrate that gradual MMA during mild and moderate dynamic exercise progressively decreases SBRS. In addition, baroreflex control of HR is progressively reset to higher blood pressure and HR in proportion to the extent of MMA.

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Section: Discussionmentioning

confidence: 96%

Progressive muscle metaboreflex activation gradually decreases spontaneous heart rate baroreflex sensitivity during dynamic exercise

Sala‐Mercado

Ichinose

Coutsos³

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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“…A possibility that a reflex originating muscle mechanoreceptors activated by actual contraction may modify the cardiac component of carotid sinus baroreflex cannot be excluded. Indeed, McWilliam et al (30) reported that cardiac vagal bradycardia in response to carotid sinus pressure elevation was inhibited at the start of evoked muscle contraction in decerebrate cats. Drew et al (9) also reported that passive calf muscle stretch with concurrent muscle metaboreflex activation following exercise reduced the maximal gain of the cardiac component of carotid sinus baroreflex in humans.…”

Section: Discussionmentioning

confidence: 97%

Differential effect of central command on aortic and carotid sinus baroreceptor-heart rate reflexes at the onset of spontaneous, fictive motor activity

Matsukawa

Ishii

Kadowaki

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

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Our laboratory has reported that central command blunts the sensitivity of the aortic baroreceptor-heart rate (HR) reflex at the onset of voluntary static exercise in conscious cats and spontaneous contraction in decerebrate cats. The purpose of this study was to examine whether central command attenuates the sensitivity of the carotid sinus baroreceptor-HR reflex at the onset of spontaneous, fictive motor activity in paralyzed, decerebrate cats. We confirmed that aortic nerve (AN)-stimulation-induced bradycardia was markedly blunted to 26 ± 4.4% of the control (21 ± 1.3 beats/min) at the onset of spontaneous motor activity. Although the baroreflex bradycardia by electrical stimulation of the carotid sinus nerve (CSN) was suppressed (P < 0.05) to 86 ± 5.6% of the control (38 ± 1.2 beats/min), the inhibitory effect of spontaneous motor activity was much weaker (P < 0.05) with CSN stimulation than with AN stimulation. The baroreflex bradycardia elicited by brief occlusion of the abdominal aorta was blunted to 36% of the control (36 ± 1.6 beats/min) during spontaneous motor activity, suggesting that central command is able to inhibit the cardiomotor sensitivity of arterial baroreflexes as the net effect. Mechanical stretch of the triceps surae muscle never affected the baroreflex bradycardia elicited by AN or CSN stimulation and by aortic occlusion, suggesting that muscle mechanoreflex did not modify the cardiomotor sensitivity of aortic and carotid sinus baroreflex. Since the inhibitory effect of central command on the carotid baroreflex pathway, associated with spontaneous motor activity, was much weaker compared with the aortic baroreflex pathway, it is concluded that central command does not force a generalized modulation on the whole pathways of arterial baroreflexes but provides selective inhibition for the cardiomotor component of the aortic baroreflex.

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“…Finally, it remains to be determined whether such modulation of arterial baroreflex responses at the onset of exercise in humans is attributable to a reduced baroreflex sensitivity (i.e., reduced maximal gain) (200,215) or rapid resetting of the baroreflex function curve (254,255). However, work by Dicarlo and Bishop (54) in conscious rabbits identified the importance of an immediate baroreflex resetting in mediating the increases in renal sympathetic outflow, BP, and HR at the onset of exercise.…”

Section: Arterial Baroreflex At Exercise Onsetmentioning

confidence: 94%

Autonomic Adjustments to Exercise in Humans

Fisher

Young

Fadel

2015

Comprehensive Physiology

227

253

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Autonomic nervous system adjustments to the heart and blood vessels are necessary for mediating the cardiovascular responses required to meet the metabolic demands of working skeletal muscle during exercise. These demands are met by precise exercise intensity-dependent alterations in sympathetic and parasympathetic nerve activity. The purpose of this review is to examine the contributions of the sympathetic and parasympathetic nervous systems in mediating specific cardiovascular and hemodynamic responses to exercise. These changes in autonomic outflow are regulated by several neural mechanisms working in concert, including central command (a feed forward mechanism originating from higher brain centers), the exercise pressor reflex (a feed-back mechanism originating from skeletal muscle), the arterial baroreflex (a negative feed-back mechanism originating from the carotid sinus and aortic arch), and cardiopulmonary baroreceptors (a feed-back mechanism from stretch receptors located in the heart and lungs). In addition, arterial chemoreceptors and phrenic afferents from respiratory muscles (i.e., respiratory metaboreflex) are also capable of modulating the autonomic responses to exercise. Our goal is to provide a detailed review of the parasympathetic and sympathetic changes that occur with exercise distinguishing between the onset of exercise and steady-state conditions, when appropriate. In addition, studies demonstrating the contributions of each of the aforementioned neural mechanisms to the autonomic changes and ensuing cardiac and/or vascular responses will be covered.

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Changes in the baroreceptor reflex at the start of muscle contraction in the decerebrate cat.

Cited by 43 publications

References 19 publications

Progressive muscle metaboreflex activation gradually decreases spontaneous heart rate baroreflex sensitivity during dynamic exercise

Progressive muscle metaboreflex activation gradually decreases spontaneous heart rate baroreflex sensitivity during dynamic exercise

Differential effect of central command on aortic and carotid sinus baroreceptor-heart rate reflexes at the onset of spontaneous, fictive motor activity

Autonomic Adjustments to Exercise in Humans

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