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Functions of the Cardiovascular System
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Neural factors. Coronary arteries are supplied by sympathetic vasoconstrictor (adrenergic ∝receptor) and parasympathetic vasodilator (muscarinic) fibres, but their roles are unclear. Sympathetic nerve output to the heart raises the myocardial oxygen requirement by increasing the force and rate of contraction and produces coronary arteriolar vasodilatation via the release of local metabolites. In this way, the direct sympathetic vasoconstrictor effect is ablated. Parasympathetic nerve activity to the heart reduces the myocardial oxygen requirement by slowing the heart rate, and local metabolic control leads to vasoconstriction, despite the direct vagal vasodilatory effect. Circulating adrenaline produces coronary vasodilatation via β2 receptors.
The Role of Neuropeptides in the Normal and Pathophysiological Control of Blood Flow
Published in Edwin E. Daniel, Neuropeptide Function in the Gastrointestinal Tract, 2019
Within the parasympathetic nerves, VIP coexists with the neurotransmitter acetylcholine (ACh).60–65 VIP and ACh are individually packaged, respectively, in large dense core and small agranular vesicles within cholinergic nerves.64,66,67 In the sympathetic ganglion, VIP appears to exist in separate cell bodies that differ from those containing neuropeptide Y (NPY) and catecholamines.63,65 However, some cell bodies within the parasympathetic ganglia (sphenopalatine, otic, ciliary) that are immunoreactive to VIP and/or cholineacetyltransferase also coreact with antiserum to NPY. A very small proportion of these cell bodies contain the adrenergic enzyme tyrosine hydroxylase, but none appear to contain catecholamines.63This suggests that some VIP/ACh-containing cholinergic nerves also may be capable of releasing NPY, whereas nerves within the sympathetic ganglion release either NPY plus catecholamines or VIP.
The nervous system
Published in Peter Kopelman, Dame Jane Dacre, Handbook of Clinical Skills, 2019
Peter Kopelman, Dame Jane Dacre
A lesion of the parasympathetic nerves produces a dilated pupil that is unreactive to light or accommodation. The pupillary response to light depends on the integrity of the afferent pathways, and is lost when the retina or optic nerve is damaged. A unilateral lesion of the retina or optic nerve results in loss of the pupillary reflex when a light is shone in that eye (direct light reaction), but there will still be a response when the unaffected eye is tested (indirect light reaction).
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
OI refers to a medical condition where the HR cannot be controlled by poor baroreflex efferent innervation of the heart. This is observed commonly in elderly and astronauts. This is modelled by changing the baroreflex paramter which inturen loses the ability to make the pressure to nominal value. Figure 8 show the simulated results for the effect of orthostatic hypotension and hypertension condition on MAP and HR. At t = 60 sec a postural change from supine to standing is introduced along with reduced sympathetic gain. Due to the abnormalities in the vascular baroreceptors which happens due to postflight, age, local tumor growth, brain stem stroke etc., the MAP and HR cannot attain its steady state value which leads to orthostatic hypotension as shown in Figure 8. At t = 200 sec, postural change from standing to supine is introduced along with change in parasympathetic baroreflex gain. Due to the poor control of parasympathetic nerve system, a higher pressure and lower heartrate is observed which leads to orthostatic hypertension.
Mobile phone induced EMF stress is reversed upon the use of protective devices: results from two experiments testing different boundary conditions
Published in Electromagnetic Biology and Medicine, 2022
The main study aimed at replicating the pilot study using a sample with sufficient power. Two study arms mimicked the experimental setup of the pilot study (i.e. duration and intensity of EMF exposure, duration, and type of intervention), and two study arms tested only a mobile phone chip, which was either known to the participants or concealed (open-hidden paradigm). EMF produced marked changes in the autonomic nervous system suggesting a shift from sympathovagal balance to sympathetic activation. This indicated that a mobile phone placed near the head for 15 minutes influenced the medulla oblongata where the vagal nerve originates. The decrease in parasympathetic nerve and heightening of sympathetic activity is a typical physiological response to stressors, which in this study, showed in the vast majority of participants. RMSSD decreased in 14 out of 15 individuals from 2.9% to 22.8% (average: 9.5%) relative to a low EMF environment (baseline). The stress response also showed in an average elevation of cortisol secretion of 22.7%. The hypothalamic–pituitary–adrenal axis controls cortisol to alter the availability of glucose as part of a fight or flight response. The study’s results are hence in alignment with the stress-response hypothesis put forward by Touitou et al. (2022) which posits elevated cortisol secretion in relation to the intensity of EMF exposure. However, it extends it with regard to exposure time needed to produce elevated secretion, which in this study, was relatively short.
Influence of daytime blue-enriched bright light on heart rate variability in healthy subjects
Published in Chronobiology International, 2022
Xue Luo, Taotao Ru, Qingwei Chen, Yun Li, Yuping Chen, Guofu Zhou
The ANS comprises the sympathetic nervous and parasympathetic nervous systems, which are antagonized (Laborde et al. 2017). From the perspective of energy metabolism, sympathetic nerve function promotes energy consumption, whereas parasympathetic nerves enhance energy storage (Oldham and Ciraulo 2014). Heart rate variability (HRV) is an indicator of the autonomic nervous system which affects the modulation of cardiac rhythm, representing changes in the parasympathetic nervous system and the balance of parasympathetic and sympathetic nerves (Gonzaga et al. 2017; Laborde et al. 2017; Mackersie and Calderon-Moultrie 2016). HRV has been used to measure the physiological responses to light (Rechlin et al. 1995; Schaefer and Kratky 2006; Vanderlei et al. 2009). HRV indicators can be divided into three categories: time-domain analysis, frequency-domain analysis, and non-linear analysis (Camm et al. 1996).