And sympathetic nervous system

The regulation of the total peripheral resistance also involves the complex interactions of several mechanisms. These include baroreflexes and sympathetic nervous system activity response to neurohumoral substances and endothelial factors myogenic adjustments at the cellular level, some mediated by ion channels and events at the cellular membrane and intercellular events mediated by receptors and mechanisms for signal transduction. As examples of some of these mechanisms, there are two major neural reflex arcs (Fig. 1). Baroreflexes are derived from high-pressure barorecep-tors in the aortic arch and carotid sinus and low-pressure cardiopulmonary baroreceptors in ventricles and atria. These receptors respond to stretch (high pressure) or... 

Increased intrahepatic resistance to portal flow increases pressure on the entire splanchnic bed an enlarged spleen (splenomegaly) is a common finding in cirrhotic patient and can result in thrombocytopenia due to splenic sequestration of the platelets. Portal hypertension mediates systemic and splanchnic arterial vasodilation through production of nitric oxide and other vasodilators in an attempt to counteract the increased pressure gradient. Nitric oxide causes a fall in systemic arterial pressure unfortunately, this activates both the renin-angiotensin-aldosterone and sympathetic nervous systems and... 

General Functions of Octopamine in Arthropods. The actions of OA in invertebrates therefore are multiple and probably involve both central and peripheral sites. Moreover, as pointed out previously, many of the known actions of OA are comparable to those of NE and E in the vertebrate central and sympathetic nervous systems. These multiple effects are concerned with arousal and stress responses, increasing the responsiveness to outside stimuli, and alerting the resting animal and priming it for action and movement. It is interesting, though inconclusive, in this context to note that ants... 

The directly acting vasodilators, with the exception of calcium channel antagonists and sympathetic nervous system depressants, receive the bulk of attention in this chapter. Other chapters offer additional information on diuretics (see Chapter 21), the renin-angiotensin system (see Chapter 18), adrenergic receptor antagonists (see Chapter 11), and the calcium channel antagonists (Chapter 19). 

Both the parasympathetic and sympathetic nervous systems provide extrinsic gastrointestinal innervation. Parasympathetic stimulation increases muscle contraction of the gut, while sympathetic stimulation inhibits contractions. Stimulation of either a- or 13-adrenoceptors will result in inhibition of contractions. The intramural nervous system consists of a myenteric (Auerbach s) plexus between the circular and longitudinal muscle areas and a submucosal (Meissner s) plexus between the muscularis mucosa and the circular muscle layers. These two plexuses contain stimulatory cholinergic neurons. 

The chemical transmitters may be small molecules— notably acetylcholine, norepinephrine, epinephrine, serotonin, dopamine, or histamine. Acetylcholine and norpeinephrine are the dominant neurotransmitters in the parasympathetic and sympathetic nervous systems, respectively. Dopamine and serotonin are employed primarily in the central nervous system. Neurotransmitters may also be more complex peptides (small proteins) such as substance P, vasopressin, endorphins, and enkephalins. The latter agents are of particular importance to our considerations of opium since they represent the endogenous opiates—agents that exist within the body whose actions are mimicked by exogenous, or outside, agents such as morphine, heroin, codeine, and so on. These neurotransmitters serve to convey information between neurons across the synaptic cleft (the junction where two neurons meet) or at the neuroeffector junction (the site between neuron and an innervated organ such as muscle or secretory gland). 

Of course, you have ascertained that the nicotinic receptor was identified as such because nerve cells as well as neuromuscular cells responded to being treated with nicotine. Because of the prevalence of nicotinic receptors in both the parasympathetic and sympathetic nervous systems, you can correctly assume that drugs affecting these sites lack selectivity. In fact, there are no known beneficial uses for nicotinic agonists. To the contrary, nicotine is a POISON. 

Severe and sustained pain can cause long-lasting reflexes in the spinal cord and sympathetic nervous system that can lead to changes in the secretion of hormones and other substances and to a chronic state of increased pain... 

How did scopolamine and atropine, both components of henbane, kill King Hamlet To answer this, let s return to the autonomic nervous system. Recall the functions of the ANS that I mentioned previously. For example, it controls heart and breathing rate, intestinal motility, pupil dilation, salivation, and perspiration The two major components of the ANS, the parasympathetic and sympathetic nervous systems (see Fig. 2—4), essentially function in competition with each other to maintain... 

Sartori C, Lepori M, Scherrer U. Interaction between nitric oxide and the cholinergic and sympathetic nervous system in cardiovascular control in humans. Pharmacol Ther. 2005 106 209-220. 

Adams KF, Jr. Pathophysiologic role of the renin-angiotensin-aldosterone and sympathetic nervous systems in heart failure. Am J Health Syst Pharm. 2004 61(suppl 2) S4-S13. 

Cholinesterase inhibitors have less marked effects on vascular smooth muscle and on blood pressure than direct-acting muscarinic agonists. This is because indirect-acting drugs can modify the tone of only those vessels that are innervated by cholinergic nerves and because the net effects on vascular tone may reflect activation of both the parasympathetic and sympathetic nervous systems. The cholinomimetic effect at the smooth muscle effector tissue is minimal since few vascular beds receive cholinergic innervation. Activation of sympathetic ganglia may increase vascular resistance. 

Akers, W.S., Cross, A., Speth, R., Dwoskin, L.P., and Cassis, L.A. 2000. Renin-angiotensin system and sympathetic nervous system in cardiac pressure-overload hypertrophy. Am. J. Physiol. Heart Circ. Physiol. 279 H2797-H2806. 

This is the presence of excess fluid in the peritoneal cavity, leading to a swollen abdomen (Figure 4.3). The accumulation of ascitic fluid represents a state of sodimn excess in the body. Patients often present with hyponatraemia, but this is thought to be due to the dilutional effect of excess water rather than to low sodium. There are three theories of the cause of ascites formation. The underfill theory suggests that there is a reduction in circulating plasma volume as a result of accumulation in the splanchnic area due to vascular dilatation in portal hypertension. This activates the plasma renin, aldosterone and sympathetic nervous systems, which leads to sodium and water retention by the kidneys. 

Beta-adrenoceptor blockers. The realisation that the coiuse of chronic heart failure can be adversely affected by activation of the renin-angiotensin-aldosterone and sympathetic nervous systems led to exploration of possible benefit from P-adrenoceptors in a condition where, paradoxically, such drugs can have an adverse effect. Clinical trials have, indeed, shown that bisoprolol, carvedilol or metoprolol lower mortality and decrease hospitalisation when added to diuretics, digoxin and an ACE inhibitor (see below). 

Sundar SK, Cierpial MA, Kilts C, Ritchie JC, Weiss JM (1990) Brain IL-1-induced immunosuppression occurs through activation of both pituitary-adrenal axis and sympathetic nervous system by corticotropin-releasing factor. J Neurosci 10 3701-3706. 

The RAAS is a complex endogenous system that is involved with most regulatory components of arterial BP. Activation and regulation are governed primarily by the kidney (Fig. 13-1). The RAAS regulates sodium, potassium, and fluid balance. Therefore, this system significantly influences vascular tone and sympathetic nervous system activity and is the most influential contributor to the homeostatic regulation of BP. 

Many factors contribute to ventricular remodehng, including neurohormonal factors (e.g., activation of the renin-angiotensin-aldosterone and sympathetic nervous systems), hemodynamic factors, mechanical factors, and changes in gene expression. This process affects both cardiomyocytes (cardiomyocyte hypertrophy, loss of cardiomyocytes) and the extracellular matrix (increased interstitial fibrosis), thereby promoting both systohc and diastohc dysfunction. ... 

NB, ganglioneuroblastoma, and ganglioneuroma are members of the family of neurobiastic tumors of the adrenal gland and sympathetic nervous system, which are derived from migrating neuroectodermal tumors... 

Schwab M, Shimada H, Joshi V, Brodeur GM. Neuroblastic tumors of adrenal gland and sympathetic nervous system. In Kleihues P, Cavenee WK, eds. World Health Organization Classification of Tumours. Tumours of the Nervous System. Lyon, Prance lARC Press 2000. 

NPY is predominandy located within neurons of the central and sympathetic nervous systems (Lundberg et al., 1984 Miyachi et al., 1986), with widespread distribution throughout the CNS. NPY has been identified in the hypothalamus (Chronwall et al., 1985 de Quidt and Emson, 1986). The concentrations of NPY in this region are compared with other central sites in Table 2. 

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