Muscle electrolyte concentrations

The concentrations and distribution of electrolytes are not fixed, because cell membranes are permeant to ions and to water. Movement of ions and water in and out of cells is determined by the balance of thermodynamic forces, which are normally close to equilibrium. Selective changes of ion concentrations cause movement of water in or out of cells to compensate for these alterations. The kidneys are a major site where changes in salt or water are sensed. The loss of fluids due to illness or disease may alter intracellular and extracellular electrolyte concentrations, with attendant changes in fluid movement in or out of cells. Changes of extracellular or intracellular ion concentrations, particularly for potassium, sodium, and calcium, can have profound effects on neuronal excitability and contractility of the heart and other muscles. 

The measurement of electrolytes in blood cells is under investigation, but on the whole the results are not too promising. There is evidence that the serum concentration of some electrolytes poorly reflects the electrolyte concentration in the tissues. Therefore, devices are that enable the measurement of electrolytes in vivo in muscle or bone are required. 

Figiue 4b, b show the calibration lines (muscle potential and consumed energy, respectively) for muscles sensing the working electrolyte concentration after three different times of current flow. Figiue 4c, c show the calibration lines for the muscle thermal sensor and Fig. 4d, d for the muscle current sensor from similar results to those shown by Fig. 4a attained now at different temperatures or under flow of different constant currents. Theoretical and experimental results as thermal, mechanical, chemical and electrical sensors for different conducting polymers and electrolytes have been reviewed recently (Otero and Martinez 2015). 

Fig. 4 Anodic experimental (full lines) and theoretical (dotted lines) chronopotentiograms (evolution of the muscle potential) obtained by flow of 0.75 mA through a polypyrrole/tape bilayer muscles including 1.6 mg of active pPy describing every time a movement of iz/2 radians in a different concentration of LiC104 aqueous solution, (b) Experimental and theoretical (Eqs. 8 and 9) muscle potentials after flow of three (always the same) intermediate charges when the muscles go through the same intermediate angles, in different electrolyte concentrations, (c) at different temperatures, and (d) imder different driving currents (b ) evolution of the experimental and theoretical consumed electrical energies after the same times of current flow as a function of the electrolyte concentration (c ) at different temperatures and (d ) under different apphed currents (Reproduced from Otero et al. (2012), Martinez and Otero (2012) with permission of the ACS)...

The posterior pituitary is innervated by direct nervous stimulation from the hypothalamus, resulting in the release of specific hormones. The hypothalamus synthesizes two hormones, oxytocin and vasopressin. These hormones are stored in and released from the posterior pituitary lobe. Oxytocin exerts two actions (1) it promotes uterine contractions during labor, and (2) it contracts the smooth muscles in the breast to stimulate the release of milk from the mammary gland during lactation. Vasopressin is an antidiuretic hormone (ADH) essential for proper fluid and electrolyte balance in the body. Specifically, vasopressin increases the permeability of the distal convoluted tubules and collecting ducts of the nephrons to water. This causes the kidney to excrete less water in the urine. Consequently, the urine becomes more concentrated as water is conserved. 

In contrast to other analytical methods, ion-selective electrodes respond to an ion activity, not concentration, which makes them especially attractive for clinical applications as health disorders are usually correlated to ion activity. While most ISEs are used in vitro, the possibility to perform measurements in vivo and continuously with implanted sensors could arm a physician with a valuable diagnostic tool. In-vivo detection is still a challenge, as sensors must meet two strict requirements first, minimally perturb the in-vivo environment, which could be problematic due to injuries and inflammation often created by an implanted sensor and also due to leaching of sensing materials second, the sensor must not be susceptible to this environment, and effects of protein adsorption, cell adhesion, and extraction of lipophilic species on a sensor response must be diminished [13], Nevertheless, direct electrolyte measurements in situ in rabbit muscles and in a porcine beating heart were successfully performed with microfabricated sensor arrays [18],... 

Electrolyte imbalances alter the voltage sensitivity of muscle ion channels. While the effect of changing ionic concentrations across cellular membranes on membrane... 

The concentrations of sodium, potassium (and chloride) ions in the body are high and make the largest contribution to the electrical charge of cells hence they are known as electrolytes. They have two important roles maintenance of the total solute concentration in the cell which prevents excessive movement of water into or out of cells through osmosis and the controlled movement of these ions across cell membranes acts as a signalling mechanism (e.g. the action potential in neurones and muscle. Chapter 14). Severe disruption of sodium or potassium levels in the body interferes with this signalling mechanism and with osmotic balance in cells. 

In polyelectrolyte gels the variation of pH or salt concentration (cs) causes a swelling or shrinkage. Therefore, in this case chemical energy is transformed to mechanical work (artificial muscles). An increase of cs (or a decrease of temperature) makes the gel shrink. Usually, the shrinking process occurs smoothly, but under certain conditions a tiny addition of salt leads to the collapse of the gel [iii, iv]. Hydration of macroions also plays an important role, e.g., in the case of proton-conductive polymers, such as -> Nafion, which are applied in -rfuel cells, -> chlor-alkali electrolysis, effluent treatment, etc. [v]. Polyelectrolytes have to be distinguished from the solid polymer electrolytes [vi] (- polymer electrolytes) inasmuch as the latter usually contain an undissociable polymer and dissolved small electrolytes. 

Most doctors use the plasma concentrations of creatinine, urea and electrolytes to determine renal function. These measures are adequate to determine whether a patient is suffering from kidney disease. Protein and amino acid catabolism results in the production of ammonia, which in turn is converted via the urea cycle into urea, which is then excreted via the kidneys. Creatinine is a breakdown product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body (depending on muscle mass). Creatinine is mainly filtered by the kidney, though a small amount is actively secreted. There is little to no tubular reabsorption of creatinine. If the filtering of the kidney is deficient, blood levels rise. 

Acute renal tubular damage occurs in association with the liver damage, together with muscle necrosis and hyperkalemia. The muscle necrosis, as demonstrated at autopsy in fatal cases (82), can itself exacerbate the severe electrolyte derangement, particularly marked hyperkalemia, that occurs in liver failure. The measurement of serum concentrations of coagulation factors V (below 10%) and VIII (VIII/V ratio over 30) can have predictive value and can thus be helpful in selecting patients who require hver transplantation (SEDA-17, 99). 

The treatment of acute episodes of exertional rhabdomyolysis is aimed at alleviating pain and muscle contracture, correcting electrolyte and/or body fluid deficiencies and addressing renal dysfunction, if present. Horses with chronic problems typically benefit more from preventative management strategies, such as the combination of a diet low in carbohydrates (concentrates) with increased daily exercise (compared with stall confinement). Supplementation of horses with fats, in the form of corn oil or rice bran, has shown considerable promise. 

Maintenance of water homeostasis is paramount to life for all organisms. In mammals, the maintenance of osmotic pressure and water distribution in the various body fluid compartments is primarily a function of the four major electrolytes, Na", K , Cl", and HCOi". In addition to water homeostasis, these electrolytes play an important role in the maintenance of pH, proper heart and muscle function, oxidation-reduction reactions, and as cofactors for enzymes. Indeed, there are almost no metabolic processes that are not dependent on or affected by electrolytes. Abnormal concentrations of electrolytes may be either the cause or the consequence of a variety of disorders. Thus determination of electrolytes is one of the most important functions of the clinical laboratory. Interpretation of abnormal osmolality and acid-base values requires specific knowledge of the electrolytes. Because of their physiological and clinical interrelationship, this chapter discusses determination. of electrolytes, osmolality, acid-base status, and blood oxygenation. 

The concentration of serum electrolytes may also be altered secondary to the development of respiratory alkalosis. The serum chloride concentration is usually slightly increased, and serum potassium concentration may be slightly decreased. Clinically significant hypokalemia can be a consequence of extreme respiratory alkalosis, although the effect is usually very small or negligible. Serum phosphorus concentration may decrease by as much as 1.5 to 2.0 mg/dL because of the shift of inorganic phosphate into cells. Reductions in the blood ionized calcium concentration may be partially responsible for symptoms such as muscle cramps and tetany. Approximately 50% of calcium is bound to albumin, and an increase in pH results in an increase in binding." ... 

Fluids move through the body continuously. The heart pumps the blood, pressure is exerted on the vessels from outside the body, and muscles relax and contract to help the heart move the fluid through the vascular system. Fluid moves into and out of the cells and the extracellular spaces by osmotic pressure. This is the pressure exerted by the flow of water through a semipermeable membrane separating two solutions with different concentrations of solute. Osmotic pressure is determined by the concentration of the electrolytes and other solutes in water and is expressed as osmolarity or osmolality. However, the terms are used interchangeably. 

In order for a muscle to contract, the concentration of potassium inside the cell moves out and is replaced by sodium, which is the prevalent electrolyte outside the cell (see Sodium). These electrol5des reverse position when the muscle repolarizes. The concentration of potassium and sodium is maintained by the sodium-potassium pump found in cell membranes. The sodium-potassium pump uses adenosine triphosphate (ATP) to pump potassium back into the cell and sodium out of the cell. 

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