Muscle contractile

In the presence of calcium, the primary contractile protein, myosin, is phosphorylated by the myosin light-chain kinase initiating the subsequent actin-activation of the myosin adenosine triphosphate activity and resulting in muscle contraction. Removal of calcium inactivates the kinase and allows the myosin light chain to dephosphorylate myosin which results in muscle relaxation. Therefore the general biochemical mechanism for the muscle contractile process is dependent on the avaUabUity of a sufficient intraceUular calcium concentration. 

Physiologically muscle-derived NO regulates skeletal muscle contractility and exercise-induced glucose uptake. nNOS is located at the plasma membrane of skeletal muscle and facilitates diffusion of NO to the vasculature to regulate muscle perfusion. 

Somatostatin acts on various organs, tissues and cells as neurotransmitter, paracrine/autocrine and endocrine regulator on cell secretion, smooth muscle contractility, nutrient absorption, cell growth and neurotransmission [1]. Some of its mainly inhibitory effects are listed in Table 1. Somatostatin mediates its function via a family of heptahelical G-protein-coupled receptors termed... 

Heart Blood vessels Increase in heart rate, heart muscle contractility, increase in speed of atrioventricular conduction P Decrease in heart rate, decrease in heart muscle contractility... 

Asthma is a complex respiratory disorder that involves mast cell degranulation, mucous secretions, and smooth muscle hypertrophy and hyperresponsiveness. Smooth muscle hyperresponsiveness has suggested some defect in the regulation of smooth muscle contractility. Therefore, a number of studies concerning asthma have centered on whether alterations in the regulation of smooth muscle contraction (Figure 4) are responsible for hyperactivity in asthmatic airway smooth muscle. 

Bigland-Ritchie, B. Woods, J.J. (1984). Changes in muscle contractile properties and neural control during human muscular fatigue. Muscle Nerve 7. 691-699. 

Methylxanthines, especially caffeine, affect skeletal muscle contractility-... 

List the factors that may alter smooth muscle contractile activity... 

All of these factors (ANS stimulation, blood-borne and locally produced substances) alter smooth muscle contractile activity by altering the intracellular concentration of calcium. An increase in cytosolic calcium leads to an increase in crossbridge cycling and therefore an increase in tension... 

Mast cell-dependent alterations in smooth muscle contractility and intestinal permeability may also be important in expulsion of H. polygyms and T. spiralis. Increases in smooth muscle contractility (with associated... 

Vallance, B.A., Blennerhasset, P.A. and Collins, S.M. (1997) Increased intestinal muscle contractility and worm expulsion in nematode-infected mice. American Journal of Physiology 272, G321-G327. 

Herrera MD, Zarzuelo A, Jimenez J, Marhuenda E, Duarte J. 1996. Effects of flavonoids on rat aortic smooth muscle contractility structure-activity relationships. Gen Pharmacol 27 273-277. 

A 75-year-old female in congestive heart failure (CHF) is unable to climb a flight of stairs without experiencing shortness of breath. Digoxin is administered to improve cardiac muscle contractility. Within two weeks, she has a marked improvement in her symptoms. What cellular action of digoxin accounts for this ... 

Na+] and, secondarily, increase cytosolic [Ca2+], which then increases heart muscle contractility. This is the presumed cardiotonic mechanism of digitalis and related cardiosteroids. 

Obviously, the effects of tamoxifen and derivatives and of raloxifene on L-type calcium channels from aortic and other blood vessels would reduce vascular smooth muscle contractility. This action, in synergy with the aforementioned effect on BK channels, would reduce blood peripheral resistance and blood pressure, which may partially account for the reduction in cardiovascular risk (Da Costa et al. 2004 Trump et al. 1992) (Fig. 4.1). 

Taggart MJ, Wray S 1998 Contribution of sarcoplasmic reticular calcium to smooth muscle contractile activation gestational dependence in isolated rat uterus. J Physiol 511 133—144... 

Holton My understanding is that the vena cava is a tonic smooth muscle, and therefore it is right at one end of a spectrum of smooth muscle contractile types. This means that, it generates tension slowly, it maintains tension when it is activated and it doesn t show action potentials. Its organization may be very different from a phasic smooth muscle that normally operates by action potentials and cannot maintain tension. 

Nicholls and Skidmore (65) demonstrated that dust collected from mills with a higher prevalence of byssinosis caused greater smooth muscle contractile activity than dust from mills with a lower prevalence. Recently, Russell e al. (66) used an isolated tissue bath to measure canine trachealis muscle contraction caused by cotton bract extracts (CBE). Morey et al. (67) showed that cotton bract represents 20-43% of the cotton dust total thus, the findings of Paton and Davenport using cotton dust agree in principle with Russell e al., who used cotton bract. Davenport and Paton (62) found a percentage of the activity of CDE represented by a 5HT-like component, but they also found at least one more active substance in the CDE than Russell et al. (66). 

Hernandez R, Vuelvas A, Garcia A, Fragoso M, Pereda R, Ibarra C, Rojas A (2008) Calcium-Dependent Effect of Tricolorin A on Intestinal and Arterial Smooth Muscle Contractility. 7th Joint Meeting of AFERP, ASP, GA, PSE and SIE. Planta Med 74 973... 

In the area perfused by the affected vessel, inadequate supply of oxygen and glucose impairs the function of heart muscle contractile force declines. In the great majority of cases, the left ventricle (anterior or posterior wall) is involved. 

Available evidence suggests that a single unifying mechanism does not exist but rather that various vasodilators may act at different places in the series of processes that couple excitation of vascular smooth muscle cells with contraction. For example, the vasodilators known as calcium channel antagonists block or limit the entry of calcium through voltage-dependent channels in the membrane of vascular smooth muscle cells. In this way, the calcium channel blockers limit the amount of free intracellular calcium available to interact with smooth muscle contractile proteins (see Chapter 14). 

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