Mechanical events

Ishijima A, Kojima H, Funatsu T, Tokunaga M, Higuchi H, Tanaka H and Yanagida T 1998 Simultaneous observation of individual ATPase and mechanical events by a single myosin molcule during interaction with actin Ce//92 161-71... 

Excitation-contraction coupling (EC coupling) is the mechanism underlying transformation of the electrical event (action potential) in the sarcolemma into the mechanical event (muscle contraction) which happens all over the muscle. In other words, it is the mechanism governing the way in which the action potential induces the increase in the cytoplasmic Ca2+ which enables the activation of myofibrils. 

Hibberd, M.G. Trentham, D.R. (1986). Relationships between chemical and mechanical events during muscular contraction. Ann. Rev. Biophys. Chem. 15, 119-136. 

Describe the mechanical events, status of the valves, and pressure changes that take place during each phase of the cardiac cycle... 

The role of calcium in this function is not fully understood. Some researchers have proposed that calcium is the link bciwccn the electrical and mechanical events in contraction. It has been shown b vitro that when calcium ions are applied locally, muscle fibers can be triggered to contract. It has further been postulated that relaxation of muscle libels is brought about by an intracellular mechanism for reducing the coneentraliun of calcium ions availahle lo ihe muscle h lamenls. Others postulate thai contraction occurs because calcium inactivates a relaxing substance, which is released front the sarcoplasmic reticulum in the presence of ATP (adenosine iriphosphate). 

The fourth actin-bound, top-of-powerstroke state is ephemeral. In the original Lymn—Taylor model it is not clear if this fourth state is strongly or weakly bound to actin, but P release, ADP release, and force generation all occur during the transition 4 to 1. Thus, in the following discussion, we attempt to break this transition down into a series of elementary events and to explore if it is possible to order the biochemical and mechanical events and to correlate them with structural changes. 

External forces applied to tissues lead to stretching of collagen, elastic fibers, and smooth muscle in the associated ECMs as well as proteoglycan deformation and fluid flow from within the matrix. The application of these forces ultimately leads to matrix remodeling and energy storage. The question arises as to how external mechanical events trigger cellular synthesis. 

Table 5.1. Summary of the principle mechanisms of cerebral ischemic damage Mechanisms Events...

He discovered and measured heat production associated with nerve impulses and analyzed physical and chemical changes associated with nerve excitation, among other studies. In 1922 he won the Nobel Prize in physiology or medicine (with otto meyerhof) for work on chemical and mechanical events in muscle contraction, such as the production of heat in muscles. This research helped establish the origin of muscular force in the breakdown of carbohydrates while forming lactic acid in the muscle. 

Secretion occurs throughout the body from nerve ends of the brain and periphery and from endocrine and exocrine glands. Thus secretory processes influence many essential body functions and the biochemistry of secretion and its susceptibility to drug action need to be clearly understood. Mechanical events in secretion are well established but biochemical mechanisms are poorly defined. 

The answer to the energization puzzle turns out to involve a simple mechanism. Events proceed as follows ... 

Computer-Aided Engineering (CAE) Supports the analysis of design solutions by simulating the artifact under working circumstances. Typical methods are based on Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), and Mechanical Event Simulations (MES). In some cases, optimization tasks are also supported. 

The prolongation of the heart action event results from the activity of slow calcium channels in the cell membranes. These act in conceit with the fast sodium channels to maintain a longer depolarization phase of the heart. This prolongation is important in the physiological function of the heart since it defines the timing and duration of the mechanical events required for a contraction. 

A recording of the heart s bioelectrical activity is called an electrocardiogram (ECG). It is one of the most frequently measured biopotentials. The study of the heart s bioelectricity is a way of understanding its physiological performance and function. Dysfunction of the heart as a pump often shows up as a characteristic signature in the ECG because its mechanical events are preceded and initiated by electrical events. 

Equation 1 assumes that the shear stress at the interface is constant as a result of complete interfacial debonding. With good adhesion, only partial debonding or other micro-mechanical events such as transverse matrix cracking are observed, which invalidate the assumption of a constant interfacial shear stress. As a result, alternative data reduction techniques have been developed. For example, Tripathi and Jones developed the cumulative stress-transfer function, which deals with the limitations given above. This has been further refined by Lopattananon et al into the stress-transfer efficiency from which an ineffective length of that fibre in that resin can be determined. In this model, the matrix properties and frictional adhesion at debonds can be included in the analysis. It is also possible to use the three-phase stress-transfer model of Wu et al to include the properties of an interphase. 

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