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The patient with acute cardiovascular problems
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
The sinoatrial (SA) node is the pacemaker of the heart and can spontaneously become activated (depolarise) at a fixed rate. This inbuilt heartrate is around 100 beats per minute and is referred to as the rate of automaticity. Each cell of the cardiac conduction system has its own rate of automaticity, but the further down in the conduction system the cell is, the slower its rate of automaticity. In order for the heart rate to be increased in times of need and for it to slow down at times of rest, the SA node is controlled externally by the sympathetic and para-sympathetic branches of the autonomic nervous system. The sympathetic nervous system has an excitatory effect on the heart, making it beat faster during exercise, stress, pain or increased metabolic need.
Alpha Adrenergic Modulation of Impulse Initiation in Normal and Ischemic Cardiac Fibers
Published in Samuel Sideman, Rafael Beyar, Analysis and Simulation of the Cardiac System — Ischemia, 2020
We have done a series of experiments to tackle the phosphatidylinositol question, initially by using phospholipase C as a means to activate both IP3 and diacylglycerol. The major shortcoming of these experiments is that we applied phospholipase C extracellularly, so there are a lot of questions about what it is inducing; that is, is it doing precisely the same thing as would occur if it were acting within the membrane? At any rate, with phospholipase C, we saw the following: an increase in automaticity, blocked by ryanodine, but not by verapamil, suggesting that it is related to some event involving SR-calcium release rather than transsarcolemmal calcium flux. To consider diacylglycerol, we used an activated phorbol ester. This induced no change in automaticity, whatever.
Toxicology
Published in Anthony FT Brown, Michael D Cadogan, Emergency Medicine, 2020
Anthony FT Brown, Michael D Cadogan
Chronic digoxin toxicity occurs particularly in the elderly and may be precipitated by renal impairment, hypokalaemia, hypercalcaemia and drugs such as amiodarone and quinidine. Clinical manifestations include: Nausea, vomiting, diarrhoea.Sedation, confusion, delirium.Visual disturbances, such as yellow haloes (xanthopsia).Cardiac automaticity and a wide range of ventricular and supraventricular arrhythmias.
Pinocembrin ameliorates arrhythmias in rats with chronic ischaemic heart failure
Published in Annals of Medicine, 2021
Yan Guo, Cui Zhang, Tianxin Ye, Xiuhuan Chen, Xin Liu, Xiaoli Chen, Yazhou Sun, Chuan Qu, Jinjun Liang, Shaobo Shi, Bo Yang
Autonomic nervous system (ANS) is a crucial role in the pathogenesis of VAs in CIHF. On the one hand, increased sympathetic activation can lead to increased automaticity of the ventricular pacemaker cells. On the other hand, ANS also regulates early afterdepolarization (EADs) and delayed afterdepolarization (DADs) [23]. Previous studies have shown that the density of sympathetic nervous in myocardial infarction area of spontaneous VAs patients was higher than that of non-spontaneous VAs patients [24]. It is reported that the density of nervous in left stellate ganglion increased significantly after myocardial infarction caused by coronary artery balloon occlusion [25]. Moreover, sympathetic activation reduces ERP and QTc, which could be a prerequisite for circus-type re-entry [26]. Furthermore, sympathetic neurotransmitters increase excitation and conduction heterogeneity and lead to susceptibility to VAs by interacting with cardiac ion channels. Sustained sympathetic activation inhibits Kv4.3, depolarizes L-type calcium channels, and resulting in APD shortening [27, 28]. Our electrophysiological data support these published findings. At the molecular level, autonomic nerves not only acted on ion channels, but also interacted with connexin proteins extensively. Yang et al. found that the neural chemorepellent semaphoring 3a inhibits neural remodelling, reducing the accumulation of dephosphorylated Cx43, and improving the inductivity of VAs [29]. These findings are consistent with our observation that up-regulated Cx43 were parallel with the reduced incidence of VTs following pinocembrin treatment.
Sport simulation as a form of implicit motor training in a geriatric athlete after stroke: a case report
Published in Physiotherapy Theory and Practice, 2020
Sonia N. Young, William R. VanWye, Harvey W. Wallmann
Studies have shown that implicit and explicit motor sequence learning is controlled by different areas of the brain and separate neural systems (Honda et al., 1998; Reber and Squire, 1998; Sanchez and Reber, 2013; Willingham, Salidis, and Gabrieli, 2002). Implicit motor learning through practice has been shown to be more effective than explicit knowledge of a task (Sanchez and Reber, 2013). While explicit motor learning strategies rely on external cues or conscious thought processes, implicit learning involves automatic and experience-based procedural memory (Honda et al., 1998; Willingham, Salidis, and Gabrieli, 2002). Automaticity has been defined as the ability to perform skilled tasks without the need for executive control (Poldrack et al., 2005). Wu, Kansaku, and Hallett (2004) studied normal subjects and explored the physiology of how movements become automatic. It was discovered that the neural motor system becomes more capable with automatic movements. Therefore, it appears that the ability of the brain to perform automatic skills with decreased effort could aid in developing interventions. Further, implicit motor learning is preserved in patients with stroke and may be useful in rehabilitation (Meehan, Randhawa, Wessel, and Boyd, 2011; Pohl et al., 2006). However, while implicit motor learning is preserved in patients post-stoke, this is accomplished utilizing a compensatory strategy of other areas of the cortex, namely the prefrontal area, to maintain performance as compared to those without stoke (Meehan, Randhawa, Wessel, and Boyd, 2011).
Automaticity of Postural Control while Dual-tasking Revealed in Young and Older Adults
Published in Experimental Aging Research, 2020
Quek et al. (2014) also indicate that certain frequency bands are thought to capture postural movements associated with different systems. They suggest that the moderate band represents contributions from muscular proprioceptive components (Kapteyn & de Wit, 1972; Taguchi, 1978); the low band represents cerebellar contributions (Diener, Dichgans, Bacher, & Gompf, 1984); the very-low band represents contributions from the vestibular system (Cernacek, Jagr, Harman, & Vyskocil, 1973; Gantchev & Popov, 1973; Kapteyn & de Wit, 1972; Mano et al., 1976; Partridge & Kim, 1969; Soames & Atha, 1982; Taguchi, 1978); and the ultralow band represents contributions from the visual system (Berthoz, Lacour, Soechting & Vidal, 1979). The cerebellum has been recognized as important for the acquisition and execution of automatic movements (Lang & Bastian, 2002; Thach, 1998). There is also recent evidence that vestibular inputs are attenuated during active motion (movements that are a consequence of our own actions) as opposed to passive or unexpected motion (movements that result from changes in the external world) to eliminate self-generated vestibular information from orientation and postural control computations (Cullen, Brooks, Jamali, Carriot, & Massot, 2011). This suggests that movements that are more conscious would display less involvement from the vestibular system. Therefore, if certain conditions promote a shift toward increased contributions from these systems, this might indicate increased automaticity.