Which of the following statements is/are TRUE? During a normal cardiac cycle, th

Question

Which of the following statements is/are TRUE? During a normal cardiac cycle, the ventricles contract before the atria SA nodes cells have prominent plateau phases in their action potentials Inhibition of HCN channels will normally result in slowing of the heart rate Heart beats are initiated by action potentials in the atrioventricular (AV) node All of the above are true. Which of the following will would be expected to increase heart rate? Activation of beta-adrenergic receptors in heart Inhibition of muscarinic receptors in SA node of heart Binding of CAMP to HCN channels in SA node cells - Increased demand for cardiac output, such as exercise - All of the above Which of the following features of the EKG is a consequence of repolarization of ventricular cells (the falling phase of their action potentials). P-wave The size of the QRS complex The interval between P and Q The T-wave None of the above Which of the following mechanical events occur during systole Isovolumetric relaxation of ventricles Rapid filling of atrium Atrial contraction Isovolumetric contraction of ventricles None of the above Which of the following would tend to lead to an increase in cardiac stroke volume? Increased contraction of smooth muscle in aorta and in the systemic arterioles Increase in blood return to the right atrium from the vena cava Activation of K^+ channels in ventricle muscle Decrease in end-diastolic volume in left ventricle All of the above should lead to increased stroke volume

Explanation / Answer

29.
a. False: The Cardiac cycle begins with contraction of the atria and ends with ventricular relaxation.

b. False: The cardiac action potential originates in specialized cells at the right atrium called the sinoatrial (SA) node, the natural pacemaker of the heart. There is no plateau phase present in pacemaker action potentials.

c. True: HCL channel blockers are used as Heart rate reducing agents. HCN channels allow the passage of a depolarizing mixed Na and K current. HCN channels plays key role in controlling the rhythmic activity (the pacemaker current). Inhibition of HCL channel will decrease depolarization and hence heart rate.

d. False: Heart beat of the cardiac cycle are initiated by the sinoatrial node (SAN).

30. e. All of the above

31. d. In ECG, the T wave represent the recovery or the repolarization of the ventricles.

32. c, d. In Atrial systole, the atrial muscle contracts to propel blood into ventricals. Isovolumetric contraction occur during ventricle systole.

33. e. All of the above.

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.