Relevant bibliographies by topics / Acoustic nerve. Heart beat

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Academic literature on the topic 'Acoustic nerve. Heart beat'

Author: Grafiati
Published: 4 June 2021
Last updated: 12 February 2022

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Journal articles on the topic "Acoustic nerve. Heart beat"

1

Mokrane, Abdelkader, and Réginald Nadeau. "Dynamics of heart rate response to sympathetic nerve stimulation." American Journal of Physiology-Heart and Circulatory Physiology 275, no. 3 (September 1, 1998): H995—H1001. http://dx.doi.org/10.1152/ajpheart.1998.275.3.h995.

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Electrical stimulation of the right cardiac sympathetic nerve was used to achieve a step increase of norepinephrine concentration at the sinus node. The heart rate (HR) response to sympathetic stimulation was characterized by a first-order process with a time delay. For moderate to high intensities of stimulation the mean delay and time constant were 0.7 and 2.1 s, respectively, and for low intensities of stimulation they were 0.4 and 1.1 s, respectively. From the analysis of the HR response to different patterns of nerve stimulation, in vivo neurotransmitter kinetics were estimated. The time constant of norepinephrine dissipation averaged ∼9 s. These results combined with computer simulations revealed two facets of sympathetic neural control of HR: 1) negligible role of the sympathetic system in beat-to-beat regulation of HR under stationary conditions and 2) ability of HR to react relatively quickly (within a few seconds) to sharp increases in sympathetic nerve traffic.
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2

Quevedo, Dario A. C., Maria Lucia G. Lourenço, Carmen D. Bolaños, Angélica Alfonso, Carla M. V. Ulian, and Simone B. Chiacchio. "Maternal, fetal and neonatal heart rate and heart rate variability in Holstein cattle." Pesquisa Veterinária Brasileira 39, no. 4 (April 2019): 286–91. http://dx.doi.org/10.1590/1678-5150-pvb-5757.

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ABSTRACT: The aim of this study was to describe the normal values for maternal, fetal and neonatal heart rate (HR) and heart rate variability (HRV) indexes in the time domain (standard deviation of beat-to-beat interval - SDNN; root mean square of successive beat-to-beat differences - RMSSD) and the frequency domain (low frequency - LF; high frequency - HF; relationship between low and high frequency - LF/HF) in 23 Holstein cows, 23 fetuses and 18 neonates during the perinatal period. HR and HRV were calculated by fetomaternal electrocardiography (ECG). Fetomaternal measurements were taken six times prepartum (between days 234 and 279 of pregnancy) and measurements were taken in neonates six times after calving (after birth and five times weekly). HR, time and frequency domain were analyzed. No significant changes in maternal, fetal beat-to-beat interval (RR interval) or HR were found. In maternal variables, SDNN decreased significantly from 38.08±2.6ms (day 14 before calving) to 23.7±2.5ms (day 1 after calving) (p<0.05), but the RMSSD did not change significantly. HR and RR interval of calf differed statistically from the day before delivery (163±7.5bpm; 381±24.2ms) to the day after calving (131±5bpm; 472±16.2ms). Time variables (SDNN and RMSSD) and the frequency-domain variables (LF and HF) were significantly different (p<0.05) between fetal and neonatal stages. Reductions in the values of SDNN and RMSSD can reflect a sympathetic dominance. After calving, the increase in HF and decrease in LF variables can indicate activation of the vagal nerve followed by heart and respiratory modulation.
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3

Cui, Jian, Thad E. Wilson, Manabu Shibasaki, Nicole A. Hodges, and Craig G. Crandall. "Baroreflex modulation of muscle sympathetic nerve activity during posthandgrip muscle ischemia in humans." Journal of Applied Physiology 91, no. 4 (October 1, 2001): 1679–86. http://dx.doi.org/10.1152/jappl.2001.91.4.1679.

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To identify whether muscle metaboreceptor stimulation alters baroreflex control of muscle sympathetic nerve activity (MSNA), MSNA, beat-by-beat arterial blood pressure (Finapres), and electrocardiogram were recorded in 11 healthy subjects in the supine position. Subjects performed 2 min of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 2.5 min of posthandgrip muscle ischemia. During muscle ischemia, blood pressure was lowered and then raised by intravenous bolus infusions of sodium nitroprusside and phenylephrine HCl, respectively. The slope of the relationship between MSNA and diastolic blood pressure was more negative ( P < 0.001) during posthandgrip muscle ischemia (−201.9 ± 20.4 units · beat−1 · mmHg−1) when compared with control conditions (−142.7 ± 17.3 units · beat−1 · mmHg−1). No significant change in the slope of the relationship between heart rate and systolic blood pressure was observed. However, both curves shifted during postexercise ischemia to accommodate the elevation in blood pressure and MSNA that occurs with this condition. These data suggest that the sensitivity of baroreflex modulation of MSNA is elevated by muscle metaboreceptor stimulation, whereas the sensitivity of baroreflex of modulate heart rate is unchanged during posthandgrip muscle ischemia.
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4

Cui, Jian, Thad E. Wilson, and Craig G. Crandall. "Baroreflex modulation of muscle sympathetic nerve activity during cold pressor test in humans." American Journal of Physiology-Heart and Circulatory Physiology 282, no. 5 (May 1, 2002): H1717—H1723. http://dx.doi.org/10.1152/ajpheart.00899.2001.

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The purpose of this project was to test the hypothesis that baroreceptor modulation of muscle sympathetic nerve activity (MSNA) and heart rate is altered during the cold pressor test. Ten subjects were exposed to a cold pressor test by immersing a hand in ice water for 3 min while arterial blood pressure, heart rate, and MSNA were recorded. During the second and third minute of the cold pressor test, blood pressure was lowered and then raised by intravenous bolus infusions of sodium nitroprusside and phenylephrine HCl, respectively. The slope of the relationship between MSNA and diastolic blood pressure was more negative ( P < 0.005) during the cold pressor test (−244.9 ± 26.3 units · beat−1 · mmHg−1) when compared with control conditions (−138.8 ± 18.6 units · beat−1 · mmHg−1), whereas no significant change in the slope of the relationship between heart rate and systolic blood pressure was observed. These data suggest that baroreceptors remain capable of modulating MSNA and heart rate during a cold pressor test; however, the sensitivity of baroreflex modulation of MSNA is elevated without altering the sensitivity of baroreflex control of heart rate.
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5

Cui, Jian, Thad E. Wilson, and Craig G. Crandall. "Baroreflex modulation of sympathetic nerve activity to muscle in heat-stressed humans." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 282, no. 1 (January 1, 2002): R252—R258. http://dx.doi.org/10.1152/ajpregu.00337.2001.

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To identify whether whole body heating alters arterial baroreflex control of muscle sympathetic nerve activity (MSNA), MSNA and beat-by-beat arterial blood pressure were recorded in seven healthy subjects during acute hypotensive and hypertensive stimuli in both normothermic and heat stress conditions. Whole body heating significantly increased sublingual temperature ( P < 0.01), MSNA ( P < 0.01), heart rate ( P< 0.01), and skin blood flow ( P < 0.001), whereas mean arterial blood pressure did not change significantly ( P > 0.05). During both normothermic and heat stress conditions, MSNA increased and then decreased significantly when blood pressure was lowered and then raised via intravenous bolus infusions of sodium nitroprusside and phenylephrine HCl, respectively. The slope of the relationship between MSNA and diastolic blood pressure during heat stress (−128.3 ± 13.9 U · beats−1 · mmHg−1) was similar ( P = 0.31) with normothermia (−140.6 ± 21.1 U · beats−1 · mmHg−1). Moreover, no significant change in the slope of the relationship between heart rate and systolic blood pressure was observed. These data suggest that arterial baroreflex modulation of MSNA and heart rate are not altered by whole body heating, with the exception of an upward shift of these baroreflex curves to accommodate changes in these variables that occur with whole body heating.
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6

Nesvold, Anders, Morten W. Fagerland, Svend Davanger, Øyvind Ellingsen, Erik E. Solberg, Are Holen, Knut Sevre, and Dan Atar. "Increased heart rate variability during nondirective meditation." European Journal of Preventive Cardiology 19, no. 4 (June 21, 2011): 773–80. http://dx.doi.org/10.1177/1741826711414625.

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Purpose: Meditation practices are in use for relaxation and stress reduction. Some studies indicate beneficial cardiovascular health effects of meditation. The effects on the autonomous nervous system seem to vary among techniques. The purpose of the present study was to identify autonomic nerve activity changes during nondirective meditation. Materials and methods: Heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) were monitored in 27 middle-aged healthy participants of both genders, first during 20 min regular rest with eyes closed, thereafter practising Acem meditation for 20 min. Haemodynamic and autonomic data were collected continuously (beat-to-beat) and non-invasively. HRV and BPV parameters were estimated by power spectral analyses, computed by an autoregressive model. Spontaneous activity of baroreceptors were determined by the sequence method. Primary outcomes were changes in HRV, BPV, and BRS between rest and meditation. Results: HRV increased in the low-frequency (LF) and high-frequency (HF) bands during meditation, compared with rest ( p = 0.014, 0.013, respectively). Power spectral density of the RR-intervals increased as well ( p = 0.012). LF/HF ratio decreased non-significantly, and a reduction of LF-BPV power was observed during meditation ( p < 0.001). There was no significant difference in BRS. Respiration and heart rates remained unchanged. Blood pressure increased slightly during meditation. Conclusion: There is an increased parasympathetic and reduced sympathetic nerve activity and increased overall HRV, while practising the technique. Hence, nondirective meditation by the middle aged may contribute towards a reduction of cardiovascular risk.
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7

El-Hamad, Fatima, Elisabeth Lambert, Derek Abbott, and Mathias Baumert. "Relation between QT interval variability and muscle sympathetic nerve activity in normal subjects." American Journal of Physiology-Heart and Circulatory Physiology 309, no. 7 (October 2015): H1218—H1224. http://dx.doi.org/10.1152/ajpheart.00230.2015.

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Beat-to-beat variability of the QT interval (QTV) is sought to provide an indirect noninvasive measure of sympathetic nerve activity, but a formal quantification of this relationship has not been provided. In this study we used power contribution analysis to study the relationship between QTV and muscle sympathetic nerve activity (MSNA). ECG and MSNA were recorded in 10 healthy subjects in the supine position and after 40° head-up tilt. Power spectrum analysis was performed using a linear autoregressive model with two external inputs: heart period (RR interval) variability (RRV) and MSNA. Total and low-frequency power of QTV was decomposed into contributions by RRV, MSNA, and sources independent of RRV and MSNA. Results show that the percentage of MSNA power contribution to QT is very small and does not change with tilt. RRV power contribution to QT power is notable and decreases with tilt, while the greatest percentage of QTV is independent of RRV and MSNA in the supine position and after 40° head-up tilt. In conclusion, beat-to-beat QTV in normal subjects does not appear to be significantly affected by the rhythmic modulations in MSNA following low to moderate orthostatic stimulation. Therefore, MSNA oscillations may not represent a useful surrogate for cardiac sympathetic nerve activity at moderate levels of activation, or, alternatively, sympathetic influences on QTV are complex and not quantifiable with linear shift-invariant autoregressive models.
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8

Grassi, Guido, Fosca Quarti-Trevano, Gino Seravalle, Raffaella Dell’Oro, Jennifer Vanoli, Gianluca Perseghin, and Giuseppe Mancia. "Sympathetic Neural Mechanisms Underlying Attended and Unattended Blood Pressure Measurement." Hypertension 78, no. 4 (October 2021): 1126–33. http://dx.doi.org/10.1161/hypertensionaha.121.17657.

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Whether blood pressure (BP) values differ when BP is measured with or without the presence of a doctor (attended and unattended BP measurements) is controversial, and no information exists on whether and to what extent neurogenic mechanisms participate at the possible BP differences between these measurements. In this study, we assessed continuous beat-to-beat finger systolic BP and diastolic BP, heart rate, muscle, and skin sympathetic nerve traffic (microneurography) before and during BP measurement by an automatic device in the presence or absence of a doctor. This was done in 18 untreated mild-to-moderate essential hypertensive patients (age, 40.2±2.8 years, mean±SEM). During attended BP measurement, there was an increase in systolic BP, diastolic BP, heart rate, and skin sympathetic nerve traffic and a muscle sympathetic nerve traffic decrease, the peak changes being +5.3%,+8.4%,+9.4%,+30.9%, and −15.2%, respectively ( P <0.05 for all). In contrast, during unattended BP measurement, systolic BP, diastolic BP, heart rate, and skin sympathetic nerve traffic were modestly, albeit in most instances significantly, reduced, whereas muscle sympathetic nerve traffic remained almost unchanged. During unattended BP measurement, peak systolic BP was 14.1 mm Hg lower, peak heart rate was 10.6 bpm lower, and peak skin sympathetic nerve traffic was 8.5 bursts/min lower than the peak values detected during attended BP measurement. Thus the cardiovascular and neural sympathetic responses to the alerting reaction elicited by BP measurement in the presence of a doctor are almost absent during unattended BP measurement, during which, if anything, a modest cardiovascular sympathoinhibition occurs. This has important implications for comparison of studies using these different BP measurement approaches as well as for decision concerning threshold and target BP values for treatment.
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9

Hayano, Junichiro, Masaya Kisohara, Norihiro Ueda, and Emi Yuda. "Impact of Heart Rate Fragmentation on the Assessment of Heart Rate Variability." Applied Sciences 10, no. 9 (May 10, 2020): 3314. http://dx.doi.org/10.3390/app10093314.

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Heart rate fragmentation (HRF) is a type of sinoatrial instability characterized by frequent (often every beat) appearance of inflection in the R-R interval time series, despite the electrocardiograms appearing to be sinus rhythm. Because the assessment of parasympathetic function by heart rate variability (HRV) analysis depends on the assumption that the high-frequency component (HF, 0.15–0.4 Hz) of HRV is mediated solely by the cardiac parasympathetic nerve, HRF that is measured as a part of HF power confounds the parasympathetic functional assessment by HRV. In this study, we analyzed HRF in a 24-h electrocardiogram big data and investigated the changes in HRF with age and sex and its influence on the assessment of HRV. We observed that HRF is often observed during childhoods (0–20 year) and increased after 75 year, but it has a large impact on individual differences in HF power at ages 60–90.
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10

Seliem, Mohamed A., Eric T. McWilliams, and Mae Palileo. "Beat-to-beat variability of left ventricular indexes measured by acoustic quantification: Influence of heart rate and respiration—Correlation with M-mode echocardiography." Journal of the American Society of Echocardiography 9, no. 3 (May 1996): 221–30. http://dx.doi.org/10.1016/s0894-7317(96)90134-0.

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Books on the topic "Acoustic nerve. Heart beat"

1

Phasic alterations in vagal tone at the initiation and termination of progressive aerobic exercise in endurance trained and non-trained individuals. 1991.

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Phasic alterations in vagal tone at the initiation and termination of progressive aerobic exercise in endurance trained and non-trained individuals. 1990.

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Phasic alterations in vagal tone at the initiation and termination of progressive aerobic exercise in endurance trained and non-trained individuals. 1991.

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Book chapters on the topic "Acoustic nerve. Heart beat"

1

Cheshire, William P. "Cardiovagal Reflexes." In Clinical Neurophysiology, 658–73. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780190259631.003.0039.

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Cardiovagal reflexes assess the parasympathetic control of heart rate. Vagal nerve traffic’s final effect on heart rate is accessible by electrocardiography (ECG). Cardiovagal physiology has a complex basis; therefore, testing cardiovagal reflexes should be performed under controlled conditions, analyzed by a standardized method, and interpreted in light of potentially confounding variables, such as medications, sympathetic tone, and respiratory and heart rates that can alter the response. The most sensitive test is the magnitude of respiratory sinus arrhythmia in response to cyclical deep breathing. Another test of cardiovagal function is the Valsalva ratio, which is the ratio of the greatest to the least heart rate in response to respiratory straining. This ratio should always be measured in conjunction with beat-to-beat blood pressure recordings. Power spectral analysis is useful in assessing spontaneous heart rate variability. A number of less frequently utilized tests of cardiovagal function are also discussed.
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Cheshire, William P. "Autonomic Physiology." In Clinical Neurophysiology, 617–28. Oxford University Press, 2009. http://dx.doi.org/10.1093/med/9780195385113.003.0035.

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The autonomic nervous system consists of three divisions: the sympathetic (thoracolumbar), parasympathetic (craniosacral), and enteric nervous systems. The sympathetic and parasympathetic autonomic outflows involve a two-neuron pathway with a synapse in an autonomic ganglion. Preganglionic sympathetic neurons are organized into various functional units that control specific targets and include skin vasomotor, muscle vasomotor, visceromotor, pilomotor, and sudomotor units. Microneurographic techniques allow recording of postganglionic sympathetic nerve activity in humans. Skin sympathetic activity is a mixture of sudomotor and vasoconstrictor impulses and is regulated mainly by environmental temperature and emotional influences. Muscle sympathetic activity is composed of vasoconstrictor impulses that are strongly modulated by arterial baroreceptors. Heart rate is controlled by vagal parasympathetic and thoracic sympathetic inputs. Vagal influence on the heart rate is strongly modulated by respiration; it is more marked during expiration and is absent during inspiration. This is the basis for the so-called respiratory sinus arrhythmia, which is an important index of vagal innervation of the heart. Power spectral analysis of heart rate fluctuations allows noninvasive assessment of beat-to-beat modulation of neuronal activity affecting the heart. Arterial baroreflex, cardiopulmonary reflexes, venoarteriolar reflex, and ergoreflexes control sympathetic and parasympathetic influences on cardiovascular effectors. The main regulatory mechanism that prevents orthostatic hypotension is reflex arterial vasoconstriction in the splanchnic, renal, and muscular beds triggered by a decrease in transmural pressure at the level of carotid sinus baroreceptors.
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