Muscles contraction, definitions

Some sarco(endo)plasmic reticulum (SR) Ca +-ATPases (SERCA) are P-type ATPases that play a major role in muscle contraction-relaxation cycles and are responsible for transporting calcium into the lumen of the sarcoplasmic reticulum. Some definitions are useful in the discussion of Ca +-ATPases ... 

Muscle strength implies the force or torque production capacity of muscles. However, to measure strength, the term must be operationally defined. One definition modified from Clarkson [2000] states that muscular strength is the maximal amount of torque or force that a muscle or muscle groups can voluntarily exert in one maximal effort, when type of muscle contraction, limb velocity, and joint angle(s) are specified. 

Let us now consider in more detail the definitions of free energy related to enzyme reactions. Under steady state conditions, functioning enzyme complexes undergo cyclic transitions between a number of different states. These states can differ in the composition of a complex (enzyme molecule with ligands, substrates, products, low-molecular aflfectors, etc.), as well as in the conformations of an enzyme molecule. The complex s transitions are coupled with the chemical transformations of substrate molecules, the processes of association-dissociation of substrates and products, active transport of various substances, muscle contraction, etc. Most of these processes are of course associated with the energy transduction from one form to another. 

CDC Case Definition Acute onset of hypertonia and/or painful muscular contractions (usually of the muscles of the jaw and neck) and generalized muscle spasms without other apparent medical cause. 

Definitive evidence for the role of NO In Inducing relaxation of smooth muscle came from a set of experiments In which acetylcholine was added to experimental preparations of the smooth muscle cells that surround blood vessels. Direct application of acetylcholine to these cells caused them to contract, the expected effect of acetylcholine on these muscle cells. But addition of acetylcholine to the lumen of small Isolated blood vessels caused the underlying smooth muscles to relax, not contract. Subsequent studies showed that in response to acetylcholine the endothelial cells that line the lumen of blood vessels were releasing some substance that in turn triggered muscle cell relaxation. That substance turned out to be NO. 

Proteins are important in a wider variety of ways than other kinds of biomolecules. As enzymes they serve as catalysts in biological synthesis and degradation reactions. As hormones they serve a regulatory role, and as antibodies they protect us against disease. They make up the muscle fibers that contract so that we can move. And proteins are the major constituents of cellular and intracellular membranes, skin, hair, muscle, and tendons. Each individual protein has its own group of amino acids arranged in a definite molecular structure that is specific to the function of that protein. 

In certain organs the onset of transamination is definitely coincident with critical stages of functional differentiation, e.g., in muscle — with the time of appearance and accumulation of phosphocreatine and establishment of rapid contraction (Koshtoyants and Ryabinovskaya, 103), in heart — with acquisition of definitive heart rate, in kidney — with the beginning of active excretory function. In the early period of postnatal life transamination values gradually increase, and only at the age of one month do they approach the levels characteristic of adult rabbits. 

One of the possible causes of the receptor reserve is demonstrated by the all or none response, e.g. in smooth-muscle cells. A single effector unit. Le. a single smooth-muscle cell, either contracts maximally or does not contract at all. This reaction of a single unit is evoked at a certain drug concentration, and thus at a certain RA concentration and at a definite stimulus value. Even if the stimulus is increased no further enhancement of the reaction of the single unit is possible. 

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