Muscle contraction description

Description of Method. Creatine is an organic acid found in muscle tissue that supplies energy for muscle contractions. One of its metabolic products is creatinine, which is excreted in urine. Because the concentration of creatinine in urine and serum is an important indication of renal function, rapid methods for its analysis are clinically important. In this method the rate of reaction between creatinine and picrate in an alkaline medium is used to determine the concentration of creatinine in urine. Under the conditions of the analysis, the reaction is first-order in picrate, creatinine, and hydroxide. 

Describe the generally accepted sliding filament model of muscle contraction. List some uncertainties in this description. 

Calcium performs a variety of cellular functions in muscle and nerve that ultimately result in muscular contraction. Excellent descriptions of calcium s function in muscle and nerve are to be found in the reviews by Hoyle (37), Cohen (38), and Robertson (39). At the neuromuscular junction, the excitable cells are very sensitive to changes in extracellular concentrations of calcium. Curtis (40) and Luttgau (41) described a fall in the resting action potential and electrical resistance when the extracellular calcium concentration fell below 10 M. The action potential and electrical resistance returned to normal following addition of calcium to this vitro preparation. The magnitude of the Initial muscle membrane action potential, that which regulates the propagation of further muscle contraction, is also mediated by the extracellular calcium concentration. While the inward flow of sodium ions from the extracellular space remains the dominant factor in the mechanism of muscle membrane depolarization, calcium ion flux appears to mediate the cell s permeability to sodium ions. This effect is particularly true in cardiac tissue (W). 

Description. Potassium is an essential mineral micronutrient in human nutrition it is the major cation inside animal cells, and it is thus important in maintaining fluid and electrolyte balance in the body. Potassium is also important in allowing muscle contraction and the sending of all nerve impulses in animals. 

Description of muscle contraction has essentially evolved into two separate approaches — lumped whole muscle models and specialized crossbridge models of the sarcomere. The former seek to interpret muscle s complex mechanical properties with a single set of model elements. Muscle experiments measure muscle force and length subjected to isometric (fixed length) conditions, isotonic (fixed load) conditions, and transient analysis where either length or load is rapidly changed. 

Structural Description of the Sliding Filament Model of Muscle Contraction... 

Stretch activation of muscle is a well-described phenomenon it was the subject of The Croonian Lecture (1977) given by Pringle,and it has been extensively researched and reported in the literature over the ensuing decades. For example, the basic description becomes When active insect flight muscle is stretched, its ATPase rate increases.. . This we take as yet another demonstration of a fundamental process whereby a phosphate present in a protein can be activated, energized, as the result of an increase in hydrophobicity. It is an example of the competition for hydration between apolar and polar species, that is, an example of the apolar-polar repulsive free energy of hydration active in muscle contraction. 

Despite the above noted correlation of phenomena, current descriptions of molecular structure and resulting function of hemoglobin and myoglobin (as well as of muscle contraction to be addressed at the molecular level in Chapter 8) proceed without consideration of the consilient mechanism. th the consilient mechanism in mind, however, a distinctive way of looking at protein structure and function materializes. The availability of so many protein crystal structures from The Protein Data Bank and, as employed in our case, the capacity to... 

As reviewed in Chapter 7 with a focus on the issue of insolubility, extensive phenomenological correlations exist between muscle contraction and contraction by model proteins capable of inverse temperature transitions of hydrophobic association. As we proceed to examination of muscle contraction at the molecular level, a brief restatement of those correlations follows with observations of rigor at the gross anatomical level and with related physiological phenomena at the myofibril level. Each of the phenomena, seen in the elastic-contractile model proteins as an integral part of the comprehensive hydrophobic effect, reappear in the properties and behavior of muscle. More complete descriptions with references are given in Chapter 7, sections 7.2.2, and 7.2.3. 

Fig. 9.4. Description of muscle contraction actin, myosin and elemental contraction...

Descriptions of a muscle contraction length-stress relationship and fila-configuration... 

Fig. 9.6. Description of a muscle contraction from single twitch to tetanus...

One can study the physiology and the mechanics of cardiac function on many levels. These include details of muscle contractions from the anatomical, physiological, and model based descriptions as well as the gross functioning of the various heart chambers such as the left ventricle. Study of the chamber performance can again be carried out at the anatomical, physiological, and model based levels. This paper deals with some model based descriptions of the functioning of the left ventricle and of necessity includes some model based descriptions of muscle contraction. 

The principle of thermal recycling is also used in reactors with a boiling layer, in which the heat from the hot region of the reactor is transported to the cold region by circulating solid particles suspended in the gas flow.15 Methods of the theory of chemical reactor regulation have been successfully used in other sciences as well. We note the model of Belousov-Zhabotinskii, proposed for the description of heart disease, of spasmatic contractions of the cardiac muscle. 

A structural dilemma lies in combining a phase concept of the molecular arrangement with the molecular description of the contraction process. It is known that the movements of different myosin heads on a particular myosin thread occur asynchronously, which is evident for example, from X-ray diffraction experiments. That means that a force is generated constantly with time. The coordination of movement between every muscle cell (down to the individual actin/myosin molecule) is controlled by the excitation via the tubuli system, which is a cubosome type of membrane system, described in the previous chapter. 

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