Question

A patient is prescribed a calcium channel blocker to prevent angina (chest pain) by decreasing the demand for oxygen. What is the explanation for this pharmacological effect?

A. A drug that inhibits the entry of calcium ions into the cytoplasm of cardiac cells decreases the membrane potential, thereby making the heart beat slower, relieving the chest pain.
B. A drug that blocks the calcium channels prevents the cardiac cells from contracting, thereby relieving the chest pain.
C. A drug that inhibits the entry of calcium ions into the cytoplasm of cardiac cells decreases the force of myocardial contractility, thereby decreasing the oxygen demand, relieving the chest pain.
D. A drug that enhances the entry of calcium ions into the cytoplasm of cardiac cells decreases the force of myocardial contractility, thereby decreasing the oxygen demand, relieving the chest pain.
E. A drug that enhances the entry of calcium ions into the cytoplasm of cardiac cells increases the membrane potential, thereby making the heart beat slower, relieving the chest pain.

Answer 1

A calcium channel blocker inhibits the entry of calcium ions into the cytoplasm of cardiac cells, reducing the force of myocardial contractility and thus decreasing the oxygen demand of the heart, relieving angina.

Step-by-step explanation:

The explanation for the pharmacological effect of a calcium channel blocker in preventing angina (chest pain) is that it inhibits the entry of calcium ions into the cytoplasm of cardiac cells, resulting in a decrease in the force of myocardial contractility. This decrease in contractility leads to a decrease in the oxygen demand of the heart, relieving the chest pain. Therefore, option C is the correct answer.