Landmarks in understanding the central nervous control of the cardiovascular system (original) (raw)
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Nerve Centers Affecting the Function of the Cardiovascular System
Journal of Babol University of Medical Sciences, 2021
BACKGROUND AND OBJECTIVE: The activity of the cardiovascular system is carried out by the Autonomic Nervous System (ANS). ANS itself is controlled by multiple nerve centers. At present, there is little and scattered information about them in Persian language. The aim of this review article is to collect information about nerve centers that control ANS and their relationship with cardiovascular activity in Persian. METHODS: In this review article, by searching the international and national databases of web of science, Scopus, Google Scholar, PubMed, ISC and Magiran until 2020 and using the keywords cardiovascular system, baroreflex, the rostral ventrolateral medulla (RVLM), the caudal ventrolateral medulla (CVLM), the nucleus tractus solitarius (NTS), the hypothalamic paraventricular nucleus (PVN), the hypothalamic supraoptic nucleus (SON), amygdala, raphe nucleus, the periaqueductal gray (PAG), cuneiform nucleus (CnF), the rostral ventromedial medulla (RVM) and the pedunculopontine tegmental nucleus (PPT), data about Autonomic Nervous System were collected. FINDINGS: Evaluations have shown that the most important brain centers for regulating blood pressure are the rostral ventrolateral medulla, the nucleus tractus solitarius, the hypothalamic paraventricular nucleus, the periaqueductal gray, and raphe nucleus, which control cardiovascular activity mainly by affecting the sympathetic system. CONCLUSION: According to the results of this study, the maintenance of basal blood pressure, heart rate regulation and reflex control of blood pressure and heart rate are mainly done by autonomic and especially sympathetic nerve centers.
Autonomic processing of the cardiovascular reflexes in the nucleus tractus solitarii
Brazilian Journal of Medical and Biological Research, 1997
The nucleus tractus solitarii (NTS) receives afferent projections from the arterial baroreceptors, carotid chemoreceptors and cardiopulmonary receptors and as a function of this information produces autonomic adjustments in order to maintain arterial blood pressure within a narrow range of variation. The activation of each of these cardiovascular afferents produces a specific autonomic response by the excitation of neuronal projections from the NTS to the ventrolateral areas of the medulla (nucleus ambiguus, caudal and rostral ventrolateral medulla). The neurotransmitters at the NTS level as well as the excitatory amino acid (EAA) receptors involved in the processing of the autonomic responses in the NTS, although extensively studied, remain to be completely elucidated. In the present review we discuss the role of the EAA L-glutamate and its different receptor subtypes in the processing of the cardiovascular reflexes in the NTS. The data presented in this review related to the neurotransmission in the NTS are based on experimental evidence obtained in our laboratory in unanesthetized rats. The two major conclusions of the present review are that a) the excitation of the cardiovagal component by cardiovascular reflex activation (chemo-and Bezold-Jarisch reflexes) or by L-glutamate microinjection into the NTS is mediated by N-methyl-D-aspartate (NMDA) receptors, and b) the sympatho-excitatory component of the chemoreflex and the pressor response to L-glutamate microinjected into the NTS are not affected by an NMDA receptor antagonist, suggesting that the sympatho-excitatory component of these responses is mediated by non-NMDA receptors.
Cardiovascular neural regulation explored in the frequency domain
Circulation, 1991
A consistent link appears to exist between predominance of vagal or sympathetic activity and predominance of HF or LF oscillations, respectively: RR variability contains both of these rhythms, and their relative powers appear to subserve a reciprocal relation like that commonly found in sympathovagal balance. In this respect, it is our opinion that rhythms and neural components always interact, just like flexor and extensor tones or excitatory and inhibitory cardiovascular reflexes, and that it is misleading to separately consider vagal and sympathetic modulations of heart rate. In humans and experimental animals, functional states likely to be accompanied by an increased sympathetic activity are characterized by a shift of the LF-HF balance in favor of the LF component; the opposite occurs during presumed increases in vagal activity. In addition, LF oscillation evaluated from SAP variability appears to be a convenient marker of the sympathetic modulation of vasomotor activity. Alth...
Journal of the Autonomic Nervous System, 1996
We analyzed the discharges of 77 single neurons located in the rostral ventrolateral medulla (RVLM, n = 25), caudal ventrolateral medulla (CVLM, n = 18), lateral tegmental field (LTF, n = 19) and caudal raphe nuclei (n = 15). These recordings were made from 36 vagotomized and sinoaortic denervated cats that were either decerebrate (n = 27) or anesthetized with urethane (n = 9) and from 3 decerebrate cats with intact sinoartic and vagal nerves. These neurons were classified as sympathetic-related (n = 61) if spike triggered averaging showed that their naturally occurring discharges were correlated to either the cardiac related (2-6 Hz) or a faster (10 Hz) oscillation in inferior cardiac sympathetic nerve discharge. Neurons were classified as sympathetic-unrelated (n = 16) if they lacked these characteristics. We used autoregressive spectral techniques to detect additional slower oscillations hidden in the variability of neuronal discharge and possibly correlated to the oscillations of systolic arterial pressure (SAP). This analysis revealed the existence of a low frequency (LF) oscillation (0.12 + 0.02 Hz) in the discharges of 36 sympathetic-related and 9 sympathetic-unrelated neurons. In relation to 35 neurons in 21 animals there was also an LF component in SAP variability. In 29 instances the LF neuronal discharges and SAP variabilities were significantly correlated. In addition, there was a high frequency (HF) oscillation (0.34 + 0.06 Hz) in the discharges of 59 medullary neurons. In 56 cases the HF in neuronal discharge variability cohered to that in SAP variability. These data are the first to demonstrate the existence of an LF component in the discharges of individual medullary neurons, at least some of which were likely to be involved in the regulation of the cardiovascular system. Since these oscillations were evident in cats with section of sinoaortic and vagal nerves, they likely reflect central rhythmogenic properties.
AJP: Heart and Circulatory Physiology, 2008
Background-Analysis of spontaneous fluctuations in systolic arterial pressure (SAP) and pulse interval (PI) reveals the occurrence of sequences of consecutive beats characterized by SAP and PI changing in the same (ϩPI/ϩSAP and ϪPI/ϪSAP) or opposite (ϪPI/ϩSAP and ϩPI/ϪSAP) direction. Although the former reflects baroreflex regulatory mechanisms, the physiological meaning of ϪPI/ϩSAP and ϩPI/ϪSAP is unclear. We tested the hypothesis that ϪPI/ϩSAP and ϩPI/ϪSAP "nonbaroreflex" sequences represent a phenomenon modulated by the autonomic nervous system reflecting a feed-forward mechanism of cardiovascular regulation. Methods and Results-We studied anesthetized rabbits before and after complete autonomic blockade (guanethidineϩpropranololϩatropine, nϭ13; CAB), (2) sympathetic blockade (guanethidineϩpropranolol, nϭ15; SB), (3) parasympathetic blockade (atropine, nϭ16), (4) sinoaortic denervation (nϭ10; SAD), and (5) controlled respiration (nϭ10; CR). Nonbaroreflex sequences were defined as Ն3 beats in which SAP and PI of the following beat changed in the opposite direction. CAB reduced the number of nonbaroreflex sequences (19.1Ϯ12.3 versus 88.7Ϯ36.6, PϽ0.05), as did SB (25.3Ϯ11.7 versus 84.6Ϯ23.9, PϽ0.001) and atropine (11.2Ϯ6.8 versus 94.1Ϯ32.4, PϽ0.05). SB concomitantly increased baroreflex sensitivity (1.18Ϯ0.11 versus 0.47Ϯ0.09 ms/mm Hg, PϽ0.01). SAD and CR did not significantly affect their occurrence. Conclusions-These results suggest that nonbaroreflex sequences represent the expression of an integrated, neurally mediated, feed-forward type of short-term cardiovascular regulation able to interact dynamically with the feedback mechanisms of baroreflex origin in the control of heart period. (Circulation. 1999;99:1760-1766.)
Zanjan University of Medical Sciences, 2020
Article Info ABSTRACT 10.30699/jambs.28.126.47 Physiological experiments show that mean blood pressure is controlled by the nervous system in long-term. The nucleus tractus solitarius (NTS), located in the dorsomedial medulla oblongata is extensively recognized as an essential brain area complicated in the integration of numerous viscerosensory processes, such as respiratory, cardiovascular, hepatic gustatory, and renal regulation mechanisms. NTS is a region of the brain stem in which primary baroreceptor afferents terminate and synapse with the rostral ventrolateral medulla (RVLM) via a nitric oxidergic pathway and hence is vital in the normal control of arterial pressure (AP). The NTS as a comparator evaluates the error signals between afferents of cardiovascular receptor and central neural structures and sends signals to nuclei that normalize the circulatory variables. Furthermore, during exercise, signals from the muscle receptors reach the NTS that activate sympathetic premotor neurons and thus cause pressor and tachycardiac responses. The GABAergic interneurons of NTS may contribute to baroreceptor reflex resetting by the inhibition of the barosensitive NTS neurons, thereby enhancing the sympathetic nerve activity. The basic functions of the NTS with respect to regulating the cardiovascular system are introduced in this review. Then, the potential mechanisms underlying cardiovascular regulation are discussed with a focus on NTS functions.
Evidence for Central Organization of Cardiovascular Rhythms
Annals of the New York Academy of Sciences, 2006
Spectral analysis of heart rate and arterial pressure variabilities is a powerful noninvasive tool that is increasingly used to infer alterations of cardiovascular autonomic regulation in a variety of physiological and pathophysiological conditions such as hypertension, myocardial infarction, and congestive heart failure. A most important methodological issue to properly interpret the results obtained by the spectral analysis of cardiovascular variability signals is represented by the attribution of neurophysiological correlates to these spectral components. In this regard, recent application of spectral techniques to the evaluation of the oscillatory properties of sympathetic efferent activity in animals as well as in humans offers a new approach to a better understanding of the relationship between cardiovascular oscillations and autonomic regulation. The data so far collected seem to suggest the presence of a centrally organized neural code, characterized by excitatory and inhibitory neural mechanisms subserving the genesis and the regulation of cardiovascular oscillations concerning the major variables of autonomic regulation.