Correct Answer: A

Rationale: Diffusion is the process by which small ions such as glucose, oxygen, and carbon dioxide redistribute themselves through semipermeable membranes from areas of higher concentration to areas of lower concentration. This is how these molecules move across the cell membrane and the capillary wall. Osmosis is the process by which water moves through semipermeable membranes from areas of lower solute concentration to areas of higher solute concentration. This is how water balance is maintained across the cell membrane and the capillary wall. Blood pressure is the force exerted by the blood on the walls of the blood vessels. It is not a process by which small ions redistribute themselves through semipermeable membranes, but rather a factor that influences the movement of fluids and solutes across the capillary wall. Rehydration is the process of restoring the fluid balance in the body by drinking fluids or receiving intravenous fluids. It is not a process by which small ions redistribute themselves through semipermeable membranes, but rather a treatment for dehydration.

Correct Answer: B

Rationale: Moist skin is not a sign of dehydration, but rather a sign of adequate hydration or sweating. Dehydration can cause dry skin, mucous membranes, and lips. Dark-colored urine is a sign of dehydration, as it indicates a high concentration of waste products and a low volume of water in the urine. Dehydration can cause the kidneys to conserve water and produce less urine. High blood pressure is not a sign of dehydration, but rather a sign of fluid overload or other factors such as stress, pain, or medication. Dehydration can cause low blood pressure, as it reduces the blood volume and the cardiac output. Distended neck veins are not a sign of dehydration, but rather a sign of fluid overload or right-sided heart failure. Dehydration can cause flat neck veins, as it reduces the venous return and the central venous pressure.

Correct Answer: B

Rationale: This is incorrect because 120 to 140 mEq/L is a low range for serum sodium, which indicates hyponatremia. Hyponatremia can cause confusion, lethargy, seizures, and coma. This is correct because 135 to 145 mEq/L is the normal range of serum sodium in adults. Sodium is essential for fluid balance, nerve transmission, and muscle contraction. This is incorrect because 150 to 160 mEq/L is a high range for serum sodium, which indicates hypernatremia. Hypernatremia can cause thirst, dry mouth, agitation, and convulsions. This is incorrect because 165 to 175 mEq/L is a very high range for serum sodium, which indicates severe hypernatremia. Severe hypernatremia can cause irreversible brain damage and death.

Correct Answer: A

Rationale: Narrow, peaked T waves are a sign of hyperkalemia, which is a high level of potassium in the blood. Potassium is an electrolyte that affects the electrical activity of the heart. Hyperkalemia can cause the T waves, which represent the repolarization of the ventricles, to become narrow and peaked, indicating a rapid and excessive repolarization. ST elevation is a sign of myocardial infarction, which is a heart attack. It indicates that the myocardium, or the heart muscle, is damaged and deprived of oxygen. ST elevation is not related to the potassium level, but rather to the coronary artery blood flow. Peaked P waves are a sign of atrial hypertrophy, which is an enlargement of the atria, the upper chambers of the heart. It indicates that the atria are under increased pressure or workload. Peaked P waves are not related to the potassium level, but rather to the atrial function. Prominent U waves are a sign of hypokalemia, which is a low level of potassium in the blood. Potassium is an electrolyte that affects the electrical activity of the heart. Hypokalemia can cause the U waves, which represent the repolarization of the Purkinje fibers, to become prominent and visible, indicating a delayed and prolonged repolarization.

Correct Answer: D

Rationale: Stroke is not a cause of hyponatremia, but rather a possible complication of it. Hyponatremia is a condition where the sodium level in the blood is too low, which can affect the brain function and cause symptoms such as confusion, seizures, or coma. Stroke is a condition where the blood supply to a part of the brain is interrupted, which can cause brain damage and neurological deficits. Dehydration is not a cause of hyponatremia, but rather a cause of hypernatremia. Dehydration is a condition where the body loses more fluids than it takes in, which can affect the blood volume and the electrolyte balance. Dehydration can cause hypernatremia, which is a condition where the sodium level in the blood is too high, which can also affect the brain function and cause symptoms such as thirst, dry mouth, or lethargy. Increased secretion of aldosterone is not a cause of hyponatremia, but rather a cause of hypokalemia. Aldosterone is a hormone that regulates the sodium and potassium levels in the body by increasing the reabsorption of sodium and the excretion of potassium in the kidneys. Increased secretion of aldosterone can cause hypokalemia, which is a condition where the potassium level in the blood is too low, which can affect the muscle and nerve function and cause symptoms such as weakness, cramps, or arrhythmias. Congestive heart failure (CHF) is a cause of hyponatremia, as it is a condition where the heart is unable to pump enough blood to meet the body's needs. This can lead to fluid retention and edema, which can dilute the sodium level in the blood and cause hyponatremia. CHF can also stimulate the release of antidiuretic hormone (ADH), which increases the reabsorption of water in the kidneys and further lowers the sodium level in the blood.