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Work Capacity, Stress, Fatigue, and Recovery
Published in R. S. Bridger, Introduction to Human Factors and Ergonomics, 2017
The heart pumps blood around the body in the manner depicted in Figure 7.6. The systolic blood pressure is the pressure on the arteries when the left ventricle pumps blood into the aorta. The diastolic blood pressure is the pressure when the heart rests between beats (the “background” blood pressure). Normally, these pressures fall below 120 and 80 mmHg, respectively. The baroreflex is the homeostatic mechanism that maintains blood pressure within a narrow range. Increases in blood pressure cause the heart rate to drop, leading to a drop in blood pressure. The reflex functions on a beat to beat basis, accounting for a natural heart rate variability due to constant fine-tuning of the system. Low heart rate variability can be a symptom of heart problems. There is evidence that constant exposure to mental stressors or the failure to appraise these stressors appropriately can suppress the baroreflex causing chronic elevated blood pressure (Giarnos and Wager, 2015).
Cardiac Autonomic Dysfunction in Patients with Schizophrenia and Their Healthy Relatives
Published in Herbert F. Jelinek, David J. Cornforth, Ahsan H. Khandoker, ECG Time Series Variability Analysis, 2017
Karl-Jürgen Bär, Steffen Schulz, Andreas Voss
The evaluation of baroreflex sensitivity (BRS) is an established tool for the assessment of autonomic control of the cardiovascular system. The baroreflex or baroreceptor reflex is one of the body's homeostatic mechanisms to maintain blood pressure at nearly constant levels. The baroreflex provides a negative feedback loop in which an elevated blood pressure reflexively causes the heart rate to decrease. In contrast, diminished blood pressure reduces baroreflex activation and causes heart rate to increase. A reduction in baroreflex control of heart rate has been reported in hypertension, coronary artery disease, myocardial infarction, and heart failure (Eckberg and Sleight 1992). There are various methods to assess BRS. For patients with schizophrenia, the noninvasive sequence method is used (Bertinieri et al. 1985). Here, spontaneous sequences of at least three consecutive beats are analyzed when an increased systolic blood pressure (SBP) of at least 1 mmHg causes an increased BBI interval of at least 5 ms (bradycardic sequence) or a decreased SBP causes a decreased BBI interval (tachycardic sequence). For each sequence, the regression between the three SBP values and three BBI values is calculated and the slope (tachycardic slope: tslope; bradycardic slope: bslope) of the regression line is used as an index of BRS.
Baroreflex control model for cardiovascular system subjected to postural changes under normal and orthostatic conditions
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
V. L. Resmi, R. G. Sriya, N. Selvaganesan
A mathematical model for baroreflex control along with the cardiovascular system was proposed to study the complex interactions between autonomic nervous system and cardiovascular system for healthy and orthostatic hypotension and hypertension conditions. The simulation study indicates that the proposed integrated model with pulsatile model of heart was more close to the real time data compared to the non pulsatile model of the heart. To show the efficiency of the pulsatile model, the simulation was carried out under (i) postural changes like supine to standing and standing to supine under normal condition and (ii) OI hypotension and hypertension conditions. The robustness of the pulsatile model was verified by introducing small disturbance pressure in MAP under various postural changing conditions. However, the proposed model did not include the effects of other receptors like chemo-receptors, which also regulate MAP by sensing the level of gasses and nutrient concentrations. The model can further include the effects of change in gravity as a function of height and time during space travel including environmental effects which can be considered as future research direction.
The interplay between DNA methylation and cardiac autonomic system functioning: a systematic review
Published in International Journal of Environmental Health Research, 2023
Nayara Cristina Dos Santos Oliveira, Fernanda Serpeloni, Simone Gonçalves de Assis
The cardiac autonomic activity was assessed by heart rate (HR), pre-ejection period (PEP), respiratory sinus arrhythmia (RSA), heart rate variability (HRV), systolic and diastolic blood pressure, mean arterial pressure (MAP), baroreflex sensitivity, and respiratory sinus arrhythmia (RSA). Increases in HR and MAP, and decreases in PEP reflect sympathetic activation. Decreases in RSA reflect parasympathetic withdrawal, whilst an increase reveals parasympathetic activation (Boyce et al. 2001). Heart rate variability characterizes cardiac sympathetic and parasympathetic modulation (Task Force 1996). The period of cardiovascular data collection was standardized in the afternoon (de Rooij et al. 2012; Xia et al. 2018), in the morning (Zhong et al. 2015; Childebayeva et al. 2019; Syme et al. 2019), or adjusted for ‘time in day’ (Fan et al. 2014; Zhang et al. 2017). In general, the nonhuman model studies and the third group of our results did not mention the exact period of the day.
The ratio of heart rate to heart rate variability reflects sympathetic activity during incremental cycling exercise
Published in European Journal of Sport Science, 2022
Yukiya Tanoue, Tomohiro Komatsu, Shihoko Nakashima, Takuro Matsuda, Ryoma Michishita, Yasuki Higaki, Yoshinari Uehara
Heart rate (HR) levels during exercise are determined by the interplay between sympathetic and parasympathetic nervous activity. As exercise intensity increases, the dominance of autonomic nervous activity is shifted from parasympathetic to sympathetic nervous activity, and HR linearly increase, which is considered to be caused by baroreflex resetting (Raven, Fadel, & Ogoh, 2006; White & Raven, 2014). The baroreflex efferents are mediated through both sympathetic and parasympathetic nervous signals, which can influence the LF component of HRV (Berntson et al., 1997). Moreover, the LF component is reported to be more strongly influenced by parasympathetic activity than sympathetic activity (Randall, Brown, Raisch, Yingling, & Randall, 1991). Therefore, we hypothesized that changes in HR that are corrected by the LF components could reflect sympathetic nervous activation by showing the relative decrease in the ability of the parasympathetic nervous system to modulate HR by baroreflex resetting during exercise. The current study aimed to determine whether changes in the HR to LF ratio (Heart rate/LF) reflect sympathetic activation during exercise.