MEDizzy - A 75-year-old-wom an, hospitalized for breast cancer, was

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Adrenergic drugs

A 75-year-old-wom an, hospitalized for breast cancer, was found unconscious in her bed by a nurse. A diagnosis of cardiac arrest was made, and cardiopulmonary resuscitation was started without success. The electrocardiogram showed that the patient was in asystole. An intracardiac injection of epinephrine was given. Which of the following post receptor mechanisms most likely mediated the effect of epinephrine on cardiac contractility in this patient?

ExplanationD Epinephrine effects on the heart are due to the activation of β1 and β2 receptors. The post receptor mechanism com m on to all β receptor activation is the stimulation of adenylyl cyclase ,which in turn increases the amount of cyclic adenosine monophosphate (cAMP) in target tissues.