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Nature Reviews. Neuroscience Dec 2022
Topics: Humans; Baroreflex; Sleep; Wakefulness
PubMed: 36316500
DOI: 10.1038/s41583-022-00654-w -
Clinical Autonomic Research : Official... Oct 2000Microgravity imposes adaptive changes in the human body. This review focuses on the changes in baroreflex function produced by actual spaceflight, or by experimental... (Review)
Review
Microgravity imposes adaptive changes in the human body. This review focuses on the changes in baroreflex function produced by actual spaceflight, or by experimental models that simulate microgravity, e.g., bed rest. We will analyze separately studies involving baroreflexes arising from carotid sinus and aortic arch afferents ("high-pressure baroreceptors"), and cardiopulmonary afferents ("low-pressure receptors"). Studies from unrelated laboratories using different techniques have concluded that actual or simulated exposure to microgravity reduces baroreflex function arising from carotid sinus afferents ("carotic-cardiac baroreflex"). The techniques used to study the carotid-cardiac baroreflex, using neck suction and compression to simulate changes in blood pressure, have been extensively validated. In contrast, it is more difficult to selectively study aortic arch or cardiopulmonary baroreceptors. Nonetheless, studies that have examined these baroreceptors suggest that microgravity produces the opposite effect, ie, an increase in the gain of aortic arch and cardiopulmonary baroreflexes. Furthermore, most studies have focus on instantaneous changes in heart rate, which almost exclusively examines the vagal limb of the baroreflex. In comparison, there is limited information about the effect of microgravity on sympathetic function. A substantial proportion of subjects exposed to microgravity develop transient orthostatic intolerance. It has been proposed that alterations in baroreflex function play a role in the orthostatic intolerance induced by microgravity. The evidence in favor and against this hypothesis is reviewed.
Topics: Baroreflex; Blood Pressure; Heart Rate; Humans; Hypotension, Orthostatic; Pressoreceptors; Space Flight; Sympathetic Nervous System; Weightlessness
PubMed: 11198482
DOI: 10.1007/BF02281109 -
The Netherlands Journal of Medicine May 2004The arterial baroreflex buffers abrupt transients of blood pressure and prevents pressure from rising or falling excessively. In experimental animals, baroreceptor... (Review)
Review
The arterial baroreflex buffers abrupt transients of blood pressure and prevents pressure from rising or falling excessively. In experimental animals, baroreceptor denervation results in temporary or permanent increases in blood pressure level and variability, depending on the extent of denervation. In humans, the clinical syndrome of baroreflex failure may arise from denervation of carotid baroreceptors following carotid body tumour resection, carotid artery surgery, neck irradiation and neck trauma. The syndrome is characterised by acute malignant hypertension and tachycardia followed by labile hypertension and hypotension. Baroreflex failure can be a cause of hypertension and should also be considered in the differential diagnosis of pheochromocytoma. Patients with suspected baroreflex failure should be referred to specialised centres for diagnostic testing and treatment.
Topics: Animals; Baroreflex; Diagnosis, Differential; Heart Rate; Humans; Hypertension
PubMed: 15366697
DOI: No ID Found -
Physiological Research Dec 2016The increased prevalence of obesity in children and its complications have led to a greater interest in studying baroreflex sensitivity (BRS) in children. This review of... (Review)
Review
The increased prevalence of obesity in children and its complications have led to a greater interest in studying baroreflex sensitivity (BRS) in children. This review of BRS in children and adolescents includes subtopics on: 1. Resting values of BRS and their reproducibility, 2. Genetics of BRS, 3. The role of a primarily low BRS and obesity in the development of hypertension, and 4. Association of diabetes mellitus, BRS, and obesity. The conclusions specific to this age follow from this review: 1. The mean heart rate (HR) influences the measurement of BRS. Since the mean HR decreases during adolescence, HR should be taken into account. 2. A genetic dependency of BRS was found. 3. Low BRS values may precede pathological blood-pressure elevation in children with white-coat hypertension. We hypothesize that low BRS plays an active role in the emergence of hypertension in youth. A contribution of obesity to the development of hypertension was also found. We hypothesize that both factors, a primarily low BRS and obesity, are partially independent risk factors for hypertension in youths. 4. In diabetics, a low BRS compared to healthy children can be associated with insulin resistance. A reversibility of the BRS values could be possible after weight loss.
Topics: Adolescent; Adult; Baroreflex; Child; Diabetes Mellitus; Humans; Hypertension; Obesity
PubMed: 27539112
DOI: 10.33549/physiolres.933271 -
The Journal of Physiological Sciences :... Nov 2019A strict adequate perfusion pressure via arterial baroreflex for the delivery of oxygen to the tissues of the body is well established; however, the importance of... (Review)
Review
A strict adequate perfusion pressure via arterial baroreflex for the delivery of oxygen to the tissues of the body is well established; however, the importance of baroreflex for cerebral blood flow (CBF) is unclear. On the other hand, there is convincing evidence for arterial baroreflex function playing an important role in maintaining brain homeostasis, e.g., cerebral metabolism, cerebral hemodynamics, and cognitive function. For example, mild cognitive impairment attenuates the sensitivity of baroreflex, and Alzheimer's disease further decreases it. These clinical findings suggest that CBF and cerebral function are affected by systemic blood pressure regulation via the arterial baroreflex. However, dysfunction of arterial baroreflex is likely to affect CBF regulation as well as the underlying neuronal function, but identifying how this is achieved is arduous since neurological diseases affect systemic as well as cerebral circulation independently. Recent insights into the influence of blood pressure regulation via the arterial baroreflex on cerebral function and blood flow regulation may help elucidate this important question. This review summarizes some update findings regarding direct (autonomic regulation) and indirect (systemic blood pressure regulation) contributions of the arterial baroreflex to the maintenance of cerebral vasculature regulation.
Topics: Animals; Baroreflex; Cerebral Arteries; Cerebrovascular Circulation; Cognition; Humans
PubMed: 31444691
DOI: 10.1007/s12576-019-00704-6 -
Clinical Autonomic Research : Official... Apr 2023We describe a patient with neurogenic orthostatic hypotension (nOH) after brainstem neurosurgery in whom baroreflex-cardiovagal function was normal despite...
We describe a patient with neurogenic orthostatic hypotension (nOH) after brainstem neurosurgery in whom baroreflex-cardiovagal function was normal despite baroreflex-sympathoneural failure. We also cite other conditions entailing differential alterations in the two efferent limbs of the baroreflex. Any condition involving nOH from selective loss of sympathetic noradrenergic innervation, interference with sympathetic pre-ganglionic transmission in the thoracolumbar spinal cord, sympathectomies, or attenuated intra-neuronal synthesis, storage, or release of norepinephrine would be expected to manifest with selective baroreflex-sympathoneural dysfunction. We advise caution in relying on indices of baroreflex-cardiovagal function for diagnosing nOH, since normal values for these indices do not exclude nOH.
Topics: Humans; Hypotension, Orthostatic; Baroreflex; Norepinephrine; Blood Pressure
PubMed: 36881269
DOI: 10.1007/s10286-023-00935-z -
Italian Heart Journal. Supplement :... May 2001Arterial baroreceptors play an important role among the large number of physiological mechanisms governing the adjustment of cardiovascular system to several surrounding... (Review)
Review
Arterial baroreceptors play an important role among the large number of physiological mechanisms governing the adjustment of cardiovascular system to several surrounding conditions. By baroreceptor stimulation, arterial pressure changes can modulate both sympathetical and vagal activity and, as a consequence, heart rate, contractility and vascular resistance. In the last years, many experimental and clinical observations have shown that ischemic heart disease and heart failure can change baroreceptor reflex sensitivity and cause excessive or inappropriate activity of the sympathetic system. Several methods have been developed to measure baroreceptor sensitivity by estimating the extent of change in heart rate following blood pressure oscillations being them spontaneous or brought about by application of pharmacological or mechanical stimuli. Under normal clinical conditions these measurements can be taken as the ability to activate a sympathetic answer (hypotension) or a parasympathetic one (hypertension), with the interplay of tonic vagal or sympathetic activity. The methodology most extensively used in the clinical setting relies on intravenous administration of phenylephrine, a pure alpha-agonist drug that activates arterial baroreceptors and leads to a reflex bradycardia, which can be measured as RR interval prolongation. Baroreflex sensitivity is quantified in ms of RR interval prolongation for each mmHg of arterial pressure increase. Compared to values obtained in normal subjects (average 15 ms/mmHg) baroreflex sensitivity is significantly depressed in post-infarction patients and in patients with heart failure. The application of a mechanical stimulus is carried out by means of a positive or negative pneumatic pressure through a collar around the neck. A decrease in neck chamber pressure, by stretching carotid receptors, is sensed as an arterial pressure increase and activates reflex bradycardia at the sinus node. Finally, the analysis of spontaneous oscillations of arterial pressure and heart rate can also provide information about baroreflex control of the cardiovascular system: indeed, even small physiological variations in arterial pressure can evoke a reflex heart rate response brought about by arterial baroreceptor. The potential clinical interest of these measurements (completely non-invasive) must be still studied in large populations to define both range of normality and prognostic significance.
Topics: Baroreflex; Blood Pressure; Heart Rate; Humans
PubMed: 11388329
DOI: No ID Found -
Brazilian Journal of Medical and... Sep 1998The arterial baroreceptor reflex system is one of the most powerful and rapidly acting mechanisms for controlling arterial pressure. The purpose of the present review is... (Review)
Review
The arterial baroreceptor reflex system is one of the most powerful and rapidly acting mechanisms for controlling arterial pressure. The purpose of the present review is to discuss data relating sympathetic activity to the baroreflex control of arterial pressure in two different experimental models: neurogenic hypertension by sinoaortic denervation (SAD) and high-renin hypertension by total aortic ligation between the renal arteries in the rat. SAD depresses baroreflex regulation of renal sympathetic activity in both the acute and chronic phases. However, increased sympathetic activity (100%) was found only in the acute phase of sinoaortic denervation. In the chronic phase of SAD average discharge normalized but the pattern of discharges was different from that found in controls. High-renin hypertensive rats showed overactivity of the renin angiotensin system and a great depression of the baroreflexes, comparable to the depression observed in chronic sinoaortic denervated rats. However, there were no differences in the average tonic sympathetic activity or changes in the pattern of discharges in high-renin rats. We suggest that the difference in the pattern of discharges may contribute to the increase in arterial pressure lability observed in chronic sinoaortic denervated rats.
Topics: Animals; Baroreflex; Blood Pressure; Hypertension; Hypertension, Renal; Muscle Denervation; Pressoreceptors; Sinoatrial Node; Sympathetic Nervous System
PubMed: 9876289
DOI: 10.1590/s0100-879x1998000900015 -
Exercise and Sport Sciences Reviews 1997From the work of Potts et al. Papelier et al. and Shi et al. it is readily apparent that the arterial (aortic and carotid) baroreflexes are reset to function at the... (Review)
Review
From the work of Potts et al. Papelier et al. and Shi et al. it is readily apparent that the arterial (aortic and carotid) baroreflexes are reset to function at the prevailing ABP of exercise. The blood pressure of exercise is the result of the hemodynamic (cardiac output and TPR) responses, which appear to be regulated by two redundant neural control systems, "Central Command" and the "exercise pressor reflex". Central Command is a feed-forward neural control system that operates in parallel with the neural regulation of the locomotor system and appears to establish the hemodynamic response to exercise. Within the central nervous system it appears that the HLR may be the operational site for Central Command. Specific neural sites within the HLR have been demonstrated in animals to be active during exercise. With the advent of positron emission tomography (PET) and single-photon emission computed tomography (SPECT), the anatomical areas of the human brain related to Central Command are being mapped. It also appears that the Nucleus Tractus Solitarius and the ventrolateral medulla may serve as an integrating site as they receive neural information from the working muscles via the group III/IV muscle afferents as well as from higher brain centers. This anatomical site within the CNS is now the focus of many investigations in which arterial baroreflex function, Central Command and the "exercise pressor reflex" appear to demonstrate inhibitory or facilitatory interaction. The concept of whether Central Command is the prime mover in the resetting of the arterial baroreceptors to function at the exercising ABP or whether the resetting is an integration of the "exercise pressor reflex" information with that of Central Command is now under intense investigation. However, it would be justified to conclude, from the data of Bevegard and Shepherd, Dicarlo and Bishop, Potts et al., and Papelier et al. that the act of exercise results in the resetting of the arterial baroreflex. In addition, if, as we have proposed, the cardiopulmonary baroreceptors primarily monitors and reflexly regulates cardiac filling volume, it would seem from the data of Mack et al. and Potts et al. that the cardiopulmonary baroreceptor is also reset at the beginning of exercise. Therefore, investigations of the neural mechanisms of regulation involving Central Command and cardiopulmonary afferents, similar to those being undertaken for the arterial baroreflex, need to be established.
Topics: Animals; Baroreflex; Blood Pressure; Exercise; Humans; Vasomotor System
PubMed: 9213098
DOI: No ID Found -
Psychophysiology Dec 2013The baroreflex consists of a negative feedback loop adjusting heart activity to blood pressure fluctuations. This review is concerned with interactions between... (Review)
Review
The baroreflex consists of a negative feedback loop adjusting heart activity to blood pressure fluctuations. This review is concerned with interactions between baroreflex function and behavior. In addition to changes in baroreflex cardiac control subject to behavioral manipulations, interindividual differences in reflex function predicted psychological and central nervous features. The sensitivity of the reflex was inversely related to cognitive performance, evoked potential amplitudes, experimental pain sensitivity, and the severity of clinical pain. Possible variables moderating the strength of the associations are tonic blood pressure, gender, and psychiatric disease. It is suggested that these observations reflect inhibition of higher brain function by baroreceptor afferents. While in many cases increased baroreflex function implies stronger inhibition, individual and situational factors modulate the behavioral impact of cardiac regulation.
Topics: Autonomic Nervous System; Baroreflex; Behavior; Cognition; Humans
PubMed: 24033333
DOI: 10.1111/psyp.12136