Which of the following doses of dopamine (Intropin) results in ...

[jerry coleman]

Which of the following doses of dopamine (Intropin) results in stimulation of beta1 receptors and increased myocardial contractility?
 
  a. 1 mcg/kg/min
  b. 5 mcg/kg/min
  c. 15 mcg/kg/min
  d. 20 mcg/kg/min

Question 2

A characteristic event in junctional dysrhythmias is
 
  a. irregular rhythm.
  b. rapid depolarization to the ventricles.
  c. the spread of the impulse in two directions at once.
  d. a widened QRS.

[katkat_flores]

Answer to Question 1

B
At low dosages of 1 to 2 mcg/kg/min, dopamine stimulates dopaminergic receptors, causing renal and mesenteric vasodilation. Moderate dosages result in stimulation of beta1 receptors to increase myocardial contractility and improve cardiac output. At dosages greater than 10 mg/kg/min, dopamine predominantly stimulates alpha receptors, resulting in vasoconstriction that often negates both the beta-adrenergic and dopaminergic effects.

Answer to Question 2

C
After an ectopic impulse arises in the junction, it spreads in two directions at once. One wave of depolarization spreads upward into the atria and depolarizes them, causing the recording of a P wave on the electrocardiogram. At the same time, another wave of depolarization spreads downward into the ventricles through the normal conduction pathway, producing a normal QRS complex.