What statement describes an embolus?

Choice A rationale

Stroke volume is the volume of blood pumped from the left ventricle per beat. It is calculated as the difference between end-diastolic volume and end-systolic volume. While it is a critical measure of cardiac function, it represents the output of the heart rather than the resistance the heart must work against. Stroke volume is influenced by contractility, preload, and afterload, but it is not the term for the resistance itself encountered during the ejection phase of the cardiac cycle.

Choice B rationale

Cardiac reserve refers to the difference between the rate at which the heart pumps blood at any given time and its maximum capacity for pumping blood. it is a measure of the heart's ability to increase its output during physical exertion or stress. It indicates the health and functional flexibility of the cardiovascular system. It does not describe the specific physical resistance or pressure that the ventricles must overcome to move blood into the aorta or pulmonary artery.

Choice C rationale

Afterload is the technical term for the resistance or pressure that the ventricles must pump against to eject blood during systole. It is primarily determined by systemic vascular resistance and the pressure within the large arteries. Scientifically, if the afterload increases, such as in hypertension or aortic stenosis, the heart must work harder to open the semilunar valves and push blood out, which can eventually lead to ventricular hypertrophy and heart failure due to the chronic workload.

Choice D rationale

Preload is the initial stretching of the cardiac myocytes prior to contraction. It is related to ventricular filling and is determined by the end-diastolic volume. According to the Frank-Starling law, an increase in preload leads to a stronger contraction, up to a certain point. Preload represents the volume of blood entering the heart and the resulting "stretch" on the muscle fibers, whereas afterload represents the "squeeze" or force needed to push that blood out.

Choice A rationale

The kidneys are the primary organs responsible for the excretion of potassium, maintaining a normal serum range of 3.5 to 5.0 mEq/L. In renal failure, the glomerular filtration rate decreases, and the tubular secretion of potassium is impaired. This leads to the retention of potassium in the extracellular fluid, resulting in hyperkalemia. Since about 90 percent of daily potassium intake is excreted via the urine, any significant decline in renal function poses a high risk.

Choice B rationale

Polyuria refers to the production of abnormally large volumes of dilute urine, which is frequently seen in conditions like diabetes insipidus or the early stages of chronic kidney disease recovery. Increased urine output typically leads to an increased loss of electrolytes, including potassium, through the renal tubules. Therefore, polyuria is more commonly associated with the development of hypokalemia, rather than hyperkalemia, as the body is losing more potassium than it is retaining or taking in.

Choice C rationale

Aldosterone is a mineralocorticoid hormone that acts on the distal tubules and collecting ducts of the kidneys to promote the reabsorption of sodium and the excretion of potassium. When aldosterone levels are increased, such as in primary hyperaldosteronism, the kidneys excessively secrete potassium into the urine. This physiological process results in a decrease in serum potassium levels, or hypokalemia, rather than the elevated levels seen in hyperkalemia, which occurs when aldosterone is deficient.

Choice D rationale

Diarrhea involves the rapid transit of intestinal contents, which are naturally rich in potassium and bicarbonate. The excessive loss of fluid and electrolytes from the gastrointestinal tract during diarrheal episodes typically leads to a significant depletion of total body potassium. Consequently, the serum potassium concentration falls below the normal range, causing hypokalemia. Hyperkalemia would only occur in this context if it triggered acute renal failure due to severe dehydration and subsequent lack of excretion.