Chapter 14, Problem 20RQ

Summary Introduction

To describe: The effect of calcium channels blockers and beta receptor blockers on the heart, and the mechanism by which these drugs reduce the cardiac output.

Introduction: Ca²⁺ enters the contractile cell through voltage-gated L-type Ca²⁺ channels present in the cell membrane. When Ca²⁺ enters into the contractile cell, it opens ryanodine receptors located on the sarcoplasmic reticulum. This leads to the release of Ca²⁺ into the cytosol. The Ca²⁺ released during this process is required for heart contraction. Beta receptors can bind to epinephrine and norepinephrine that flow into the blood. These receptors play a role in increasing heart rate and contraction, and therefore, help in the cardiac output.