The relative refractory period occurs when the cardiac muscle cell has fully returned to its resting membrane potential.
True
False
The Correct Answer is B
Correct answer: False
The relative refractory period occurs during the latter part of the cardiac action potential, specifically during phase 3 (repolarization) of ventricular muscle cells. During this period, the myocardial cell has partially repolarized but has not yet fully returned to its resting membrane potential. While the cell can respond to a stronger-than-normal stimulus, normal stimuli will not trigger a contraction. Anatomically, this period applies to cardiac myocytes throughout the atria and ventricles, ensuring coordinated contractions while preventing premature or tetanic contractions, which could compromise effective cardiac output.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Correct answer: True
The endocardium is a thin, smooth membrane that lines the internal chambers of the heart, including the atria, ventricles, and heart valves. It is composed of endothelial cells and connective tissue, providing a non-thrombogenic surface that minimizes friction as blood flows through the heart. The endocardium plays a critical role in maintaining efficient circulation, regulating myocardial function, and forming the inner lining of the heart valves to ensure unidirectional blood flow. Its anatomical location within the heart chambers allows it to serve as a protective barrier between the blood and the myocardium, supporting both structural integrity and optimal cardiac performance.
Correct Answer is D
Explanation
A. The sodium ion channels open, allowing Na+ to enter the cell: Opening of sodium channels occurs during the depolarization phase of cardiac action potentials, not repolarization. The influx of Na+ rapidly raises the membrane potential, initiating the action potential and triggering subsequent calcium influx for contraction.
B. The calcium ion channels open, allowing Ca2+ to enter the cell: Calcium channels open primarily during the plateau phase (phase 2) of the cardiac action potential, allowing Ca2+ entry to sustain contraction. This occurs before repolarization and contributes to excitation-contraction coupling rather than the return to resting membrane potential.
C. Sodium ion channels close, preventing Na+ from entering: Sodium channel closure occurs immediately after depolarization and contributes to the refractory period, but it does not itself drive repolarization. The cell requires potassium efflux to restore the resting membrane potential.
D. Potassium ion channels open, allowing K+ to leave the cell: During repolarization (phase 3) of cardiac conducting cells, voltage-gated potassium channels open, permitting K+ to exit the cytoplasm. The outward movement of positively charged K+ restores the negative resting membrane potential, terminating the action potential and preparing the cell for the next depolarization.
Whether you are a student looking to ace your exams or a practicing nurse seeking to enhance your expertise , our nursing education contents will empower you with the confidence and competence to make a difference in the lives of patients and become a respected leader in the healthcare field.
Visit Naxlex, invest in your future and unlock endless possibilities with our unparalleled nursing education contents today
Report Wrong Answer on the Current Question
Do you disagree with the answer? If yes, what is your expected answer? Explain.
Kindly be descriptive with the issue you are facing.