A 55-Year-Old Man Comes to the Office for Follow-Up of Hypertension

question 114

Multiple Choice

A 55-year-old man comes to the office for follow-up of hypertension and coronary heart disease.  He has been on several medications in the past with suboptimal blood pressure control.  The physician considers adding verapamil to the patient's current regimen, as its vasodilatory properties make it useful for controlling systemic hypertension.  Verapamil also affects cardiac contractility but has a minimal effect on skeletal muscle.  Which of the following properties of skeletal muscle is responsible for its resistance to the medication?

• A)Calmodulin-independent excitation-contraction coupling
• B)Decreased troponin affinity to intracellular calcium
• C)Elaborate T-tubular system
• D)Lack of internal automaticity
• E)Little dependence on extracellular calcium influx