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Baroreceptor Reflex Components and Their Alteration in Hypertension
Published in Irving H. Zucker, Joseph P. Gilmore, Reflex Control of the Circulation, 2020
The baroreflex maintains blood pressure around a set point under normal physiological conditions. An increase in blood pressure is, therefore, expected to stimulate baroreceptors and result in reflex adjustments to revert it to control levels. In hypertensive individuals, the baroreflex mechanism maintains its capacity to buffer acute changes in blood pressure but this is done at a much higher set point. This has been described as “resetting of baroreceptors” (Kezdi, 1953). This phenomenon has also been demonstrated in renal hypertensive dogs (McCubbin, 1958) and rabbits (Aars, 1968; Angell-James, 1973, 1974a,b). In these studies, the electrical activity of the carotid sinus and aortic nerves was recorded. The threshold pressure to activate carotid sinus and aortic baroreceptors was higher in hypertensive animals when compared to that in normotensive controls. Despite high blood pressure, carotid occlusion response could still be elicited, indicating that the baroreflex was still functional.
Age-Related Changes in the Autonomic Nervous System
Published in David Robertson, Italo Biaggioni, Disorders of the Autonomic Nervous System, 2019
Sheila M. Ryan, Lewis A. Lipsitz
The baroreflex is a complex neural feedback loop that rapidly restores the blood pressure to its normal set-point during transient physiologic perturbations. This neural feedback mechanism involves: tonic signals from baroreceptors located in the carotid arteries, aortic arch, right atrium and lung to inhibitory vasomotor centers of the brainstem; central nervous system integration of these signals; efferent sympathetic and parasympathetic nerve activity; and effector organ response. Most of the current information about baroreflex function and aging is derived from measurements of cardiovascular responses to stimulation of baroreceptors. A progressive age-related impairment in baroreflex function has been well demonstrated by a reduction in the cardioinhibitory response to hypertensive stimuli such as phenylephrine infusion and phase IV of the Valsalva maneuver, and by a blunted cardioacceleratory response to hypotensive stressors such as upright posture, lower body negative pressure or nitroprusside infusion.
Cardiovascular receptors, reflexes and central control
Published in Neil Herring, David J. Paterson, Levick's Introduction to Cardiovascular Physiology, 2018
Neil Herring, David J. Paterson
The baroreflex adjusts the cardiac output and peripheral vascular tone to stabilize the arterial BP. The reflex response to an acute rise in arterial BP is described first, then the medically important response to a fall in pressure, such as occurs during hypovolaemia.
Developments in the assessment of non-motor disease progression in amyotrophic lateral sclerosis
Published in Expert Review of Neurotherapeutics, 2021
Adriano Chiò, Antonio Canosa, Andrea Calvo, Cristina Moglia, Alessandro Cicolin, Gabriele Mora
The arterial pressure is one of the most important variables that must be controlled to maintain the homeostasis. The main reflex pathway that maintains arterial pressure homeostasis is the baroreflex; the sensors of this reflex are the baroreceptors, mechanoreceptor sensory neurons that are elicited by a stretch of the blood vessels. To study the functioning of the baroreflex, two of the most common stimuli involve modifications of posture and are the head up tilt test (TILT) and the active standing (STAND). TILT is a passive transition from supine to upright position usually carried out with a rotating table [201,202] inducing a sympathetic activation and a vagal withdrawal. STAND consists of an active transition of the subject from the supine to the orthostatic position and it is also known to induce a sympathetic activation and vagal withdrawal.
Ablation of TRPV1-positive nerves exacerbates salt-induced hypertension and tissue injury in rats after renal ischemia-reperfusion via infiltration of macrophages
Published in Clinical and Experimental Hypertension, 2021
Shuang-Quan Yu, Shuangtao Ma, Donna H. Wang
A limitation of the present study is that the effects of CAP, LC, or their combination on blood pressure and renal physiology of sham rats were not investigated. Previous studies demonstrated that neither CAP nor LC affects blood pressure of normal animals (2,31). Therefore, it is likely that the phenotype of sham rats treated with CAP, LC, or CAP plus LC will be similar to rats in the sham group. Another limitation is that CAP was systemically given to the rats and that TRPV1-positive nerves in and out of the kidney could all be degenerated. Especially, the baroreflex regulation of blood pressure could be altered by CAP injection. Therefore, degeneration of TRPV1-expressing sensory nerves throughout the body contributes to the enhanced salt-sensitive hypertension and renal injury. In addition, CAP treatment in the present study likely resulted in an incomplete ablation of TRPV1-positive nerves as the reduction of TRPV1 expression was relatively small. This small reduction of TRPV1 was linked to the mild increase in salt sensitivity. A strategy to ablate TRPV1-positive renal nerves more specifically and thoroughly could be valuable for future studies.
Acute restraint stress increases blood pressure and oxidative stress in the cardiorenal system of rats: a role for AT1 receptors
Published in Stress, 2020
Gabriel T. do Vale, Drieli Leoni, Arthur H. Sousa, Natália A. Gonzaga, Daniela L. Uliana, Davi C. La Gata, Leonardo B. Resstel, Cláudia M. Padovan, Carlos R. Tirapelli
Clinical and experimental studies have shown that psychological stress has a direct impact in the cardiovascular system (Grippo & Johnson, 2009; Rozanski, Blumenthal, & Kaplan, 1999). The impact of stress in the cardiovascular system is affected by the chronicity of the stressor stimulus (Crestani, 2016). In this sense, chronic stress increases baseline values of mean arterial pressure (MAP) and heart rate (HR) (Duarte, Cruz, Leão, Planeta, & Crestani, 2015; Nalivaiko, 2011). Alterations of autonomic activity are also associated with chronic stress. In this regard, it has been described that chronic stress increased the sympathetic tone to the heart (Duarte et al., 2015) and that this response contributes to the increased susceptibility to cardiac arrhythmias (Grippo et al., 2004). Impaired baroreflex function was also described after chronic stress (Almeida, Duarte, Oliveira, & Crestani, 2015; Duarte et al., 2015). Thus, exposure to long-term stressful events is associated with enduring autonomic imbalance and cardiovascular dysfunctions (Crestani, 2016). On the other hand, acute stress induces physiological changes in the autonomic nervous system. These responses, which are mainly characterized by changes in the cardiovascular system, are short-term adaptive mechanisms to aversive threats that maintain homeostasis and ensure survival. Cardiovascular changes in response to acute stress include increase in blood pressure, HR, and cardiac output (Busnardo, Tavares, & Correa, 2014; Crestani, Tavares, Alves, Resstel, & Correa, 2010; Dos Reis, Fortaleza, Tavares, & Corrêa, 2014).