Muscle mass

The Cardiac Cycle. The heart (Eig. lb) performs its function as a pump as a result of a rhythmical spread of a wave of excitation (depolarization) that excites the atrial and ventricular muscle masses to contract sequentially. Maximum pump efficiency occurs when the atrial or ventricular muscle masses contract synchronously (see Eig. 1). The wave of excitation begins with the generation of electrical impulses within the SA node and spreads through the atria. The SA node is referred to as the pacemaker of the heart and exhibits automaticity, ie, it depolarizes and repolarizes spontaneously. The wave then excites sequentially the AV node the bundle of His, ie, the penetrating portion of the AV node the bundle branches, ie, the branching portions of the AV node the terminal Purkinje fibers and finally the ventricular myocardium. After the wave of excitation depolarizes these various stmetures of the heart, repolarization occurs so that each of the stmetures is ready for the next wave of excitation. Until repolarization occurs the stmetures are said to be refractory to excitation. During repolarization of the atria and ventricles, the muscles relax, allowing the chambers of the heart to fill with blood that is to be expelled with the next wave of excitation and resultant contraction. This process repeats itself 60—100 times or beats per minute... 

The heart, a four-chambered muscular pump has as its primary purpose the propelling of blood throughout the cardiovascular system. The left ventricle is the principal pumping chamber and is therefore the largest of the four chambers in terms of muscle mass. The efficiency of the heart as a pump can be assessed by measuring cardiac output, left ventricular pressure, and the amount of work requHed to accomplish any requHed amount of pumping. 

Anabolic steroids increase muscle mass and strength. They are used by some athletes to enhance performance. 

After die test dose , the prescribed dosage of iron is administered IM. The drug is given into the muscle mass... 

Muscle weakness, loss of muscle mass, tendon rupture, osteoporosis, aseptic necrosis of femoral and humoral heads, spontaneous fractures... 

The corticosteroids are administered with caution in older adults because they are more likely to have preexisting conditions such as congestive heart failure, hypertension, osteo-poros s and arthritis which may be worsened by the use of such agents The nurse monitors older adults for exacerbation of existing conditionsduring corticosteroid therapy. In addition, lower dosages may be needed because of the effects of aging, such as decreased muscle mass renal function, and plasma volume. 

The use of anabolic steroids to promote an increase in muscle mass and strength has become a serious problem. Anabolic Steroids are not intended for this use. Unfortunately, deathsin young, healthy individuals have been directly attributed to the use of these drugs Nurses should discourage the illegal use of anabolic steroids to increase muscle mass... 

John, a friend of your brother, has started to use anabolic steroids to increase his strength and muscle mass... 

Older adults are at increased risk for adverse reactions from the antineoplastic drugs because of the increased incidence of chronic disease, particularly renal impairment or cardiovascular disease. When renal impairment is present, a lower dosage of the antineoplastic may be indicated. Creatinine clearance isused to monitor renal function in the older adult. Blood creatinine levels are likely to be inaccurate because of a decreased muscle mass in the older adult. 

Liver weight 1800 g. Muscle mass 35 kg. Total volume 10L. 

Creatinine is formed in muscle from creatine phosphate by irreversible, nonenzymatic dehydration and loss of phosphate (Figure 31-6). The 24-hour urinary excretion of creatinine is proportionate to muscle mass. Glycine, arginine, and methionine all participate in creatine biosynthesis. Synthesis of creatine is completed by methylation of guanidoacetate by S-adenosylmethio-nine (Figure 31-6). 

In humans, skeletal muscle protein is the major nonfat source of stored energy. This explains the very large losses of muscle mass, particularly in adults, resulting from prolonged caloric undernutrition. 

Nitrogen compounds commonly determined are creatinine, urea, and uric acid. Creatinine is an end product of the energy process occurring within the muscles, and is thus related to muscle mass. Creatinine in urine is commonly used as an indicator and correction factor of dilution in urine. Creatinine in serum is an indicator of the filtration capacity of the kidney. Urea is the end product of the nitrogen luea cycle, starting with carbon dioxide and ammonia, and is the bulk compoimd of urine. The production of uric acid is associated with the disease gout. In some cases, it appears that the excess of uric acid is a consequence of impaired renal excretion of this substance. 

Whey proteins are known to increase immune response and maintain muscle mass (Phillips et ah, 2009). In one instance, when an immunosti-mulatory vitamin and mineral mixture developed at Tufts University Human Nutrition Research Center on Aging was blended with texturized WPI (TWPI) in an extruded snack bar, immunostimulatory effects were enhanced in young (< 5 months) and old (> 22 months) mice fed ad libitum for 5 weeks. The mineral mixture and TWPI improved T cell proliferation and reduced upregulated production of proinflammatory mediators in... 

Pulmonary hypertension develops late in the course of COPD, usually after the development of severe hypoxemia. It is the most common cardiovascular complication of COPD and can result in cor pulmonale, or right-sided heart failure. Hypoxemia plays the primary role in the development of pulmonary hypertension by causing vasoconstriction of the pulmonary arteries and by promoting vessel wall remodeling. Destruction of the pulmonary capillary bed by emphysema further contributes by increasing the pressure required to perfuse the pulmonary vascular bed. Cor pulmonale is associated with venous stasis and thrombosis that may result in pulmonary embolism. Another important systemic effect is the progressive loss of skeletal muscle mass, which contributes to exercise limitations and declining health status. 

Impotence is unresponsive to treatment and is associated with reduced muscle mass, loss of pubic hair, and osteoporosis. 

Physical examination of the musculoskeletal system (e.g., biceps, triceps, quadriceps, temporalis, deltoid, and interosseus muscles) for loss of muscle mass, and examination of the skin and mucous membranes for abnormalities (e.g., noting dry or flaky skin, bruising, edema, ascites, poorly healing wounds) and loss of subcutaneous fat... 

Cardiac cachexia Physical wasting with loss of weight and muscle mass caused by cardiac disease a wasting syndrome that causes weakness and a loss of weight, fat, and muscle. 

Although determination of creatinine clearance rate is a standard clinical procedure, it is difficult to carry out mainly because accurate collection of total urine output over a 24-hour period is required. It can never be certain that this requirement has been met. Since creatinine is produced continuously in muscle and is cleared by the kidney, renal failure is characterized by elevated serum creatinine levels. The degree of elevation is directly related to the degree of renal failure—if it is assumed that the production of creatinine in the muscle mass is constant and that renal function is stable. When these assumptions are valid, there is a direct relationship between serum creatinine level and kanamycin half-life, as shown in Fig. 9. The equation of the line in Fig. 9 is... 

Intramuscularly administered products typically form a depot in the muscle mass from which the drug is slowly absorbed. The peak drug concentration is usually seen within 1-2 hours. Factors affecting the drug-release rate from an IM depot include the compactness of the depot (the less compact and more diffuse, the faster the release), the rheology of the product, concentration and particle size of drug in the vehicle, nature of the solvent or vehicle, volume of the injection, tonicity of the product, and physical form of the product. 

Second, the area under the curve of the P wave is small compared to that of the QRS complex. This is related to the muscle mass of the chambers. The ventricles have significantly more muscle than the atria and therefore generate more electrical activity. Furthermore, although it may not appear to be the case given the spike-like nature of the QRS complex, areas under the QRS complex and the T wave are approximately the same. This is because these recordings represent electrical activity of the ventricles even though one is caused by depolarization and the other by repolarization. Either way, the muscle mass involved is the same. 

The Body Mass Index (BMI) is used to determine whether a person is at a healthy weight, overweight or obese. BMI has some limitations, in that it can overestimate body fat in people who are very muscular and it can underestimate body fat in people who have lost muscle mass, such as many elderly. 

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