A physician has ordered the measurement of a cardiac patient's ...

[mia]

A physician has ordered the measurement of a cardiac patient's electrolyte levels as part of the client's morning blood work.
 
  Which of the following statements best captures the importance of potassium in the normal electrical function of the patient's heart?
  A)
  Potassium catalyzes the metabolism of ATP, producing the gradient that results in electrical stimulation.
  B)
  Potassium is central to establishing and maintaining the resting membrane potential of cardiac muscle cells.
  C)
  The impermeability of cardiac cell membranes to potassium allows for action potentials achieved by the flow of sodium ions.
  D)
  The reciprocal movement of one potassium ion for one sodium ion across the cell membrane results in the production of an action potential.

Question 2

A nurse who works on a pediatric cardiology unit of a hospital is providing care for an infant with a diagnosis of tetralogy of Fallot.
 
  Which of the following pathophysiologic results should the nurse anticipate?
  A)
  There is a break in the normal wall between the right and left atria that results in compromised oxygenation.
  B)
  The aortic valve is stenotic, resulting in increased afterload.
  C)
  Blood outflow into the pulmonary circulation is restricted by pulmonic valve stenosis.
  D)
  The right ventricle is atrophic as a consequence of impaired myocardial blood supply.

[Chou]

Answer to Question 1

Ans:
B

Feedback:

The selective permeability of cell membranes to potassium, and its near-impermeability to sodium ions, produces the resting membrane potential of cardiac cells. Potassium does not catalyze the metabolism of ATP, and sodium and potassium ions do not move across the cell membrane in a 1:1 ratio.

Answer to Question 2

Ans:
C

Feedback:

Tetralogy of Fallot is marked by obstruction or narrowing of the pulmonary outflow channel, including pulmonic valve stenosis, a decrease in the size of the pulmonary trunk, or both. The characteristic septal defect is ventricular, not atrial. Aortic valve stenosis and right ventricular atrophy are not associated with the diagnosis.

[mia]

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