What is the major effect of calcium channel blockers on cardiac contractions
Increases the rate of cardiac contractions
Decreases the strength of cardiac contractions
Stabilizes the rhythm of cardiac contractions
Stabilizes the vasodilation during cardiac contractions
The Correct Answer is B
Calcium channel blockers (CCBs) are a class of medications that block the influx of calcium ions into cardiac and smooth muscle cells, leading to relaxation of these muscles and dilation of blood vessels.
In the heart, CCBs primarily affect the L-type calcium channels in the cardiac myocytes, which are responsible for the influx of calcium ions during the plateau phase of the cardiac action potential. By blocking these channels, CCBs decrease the amount of calcium that enters the cardiac myocytes, which in turn reduces the strength of cardiac contractions (i.e. contractility). 
This reduction in contractility can be beneficial in certain conditions where the heart is working too hard or experiencing insufficient blood flow, such as in hypertension, angina, or some forms of arrhythmia. By reducing the workload of the heart, CCBs can help to lower blood pressure, decrease oxygen demand, and improve blood flow to the heart.
While CCBs can also have effects on the rate and rhythm of cardiac contractions, these effects are generally less pronounced than the reduction in contractility. Some CCBs, such as verapamil and diltiazem, can slow the heart rate by blocking the L-type calcium channels in the sinoatrial (SA) and atrioventricular (AV) nodes, while others, such as nifedipine, have little effect on heart rate.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Hyperventilation refers to an increased rate and depth of breathing, which results in excessive elimination of carbon dioxide (CO2) from the body. Carbon dioxide is an acidic gas that helps regulate the pH of the blood. When too much CO2 is lost through hyperventilation, it causes a decrease in the partial pressure of carbon dioxide in the blood (PaCO2), leading to a condition called hypocapnia.
Hypocapnia can cause symptoms such as lightheadedness, dizziness, and tingling in the fingers and toes.
Correct Answer is C
Explanation
When the left ventricle is unable to pump blood effectively, blood backs up into the lungs, leading to pulmonary congestion and edema. This can cause symptoms such as shortness of breath, coughing, and wheezing. Decreased venous pressure and hyperoxygenation are not typically associated with left ventricular failure. Bradycardia may occur in some cases, but it is not a defining feature of left ventricular failure.
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