Answer: Greater cardiac filling → greater stretch of ventricle → greater force of contraction.
- A Heart rate rises proportionally with sympathetic stimulation during physical exercise
- B Greater cardiac filling → greater stretch of ventricle → greater force of contraction
- C The heart ejects a fixed stroke volume regardless of venous return changes
- D Arterial blood pressure directly sets the intrinsic rate of SA node firing each beat
Correct answer: B. Greater cardiac filling → greater stretch of ventricle → greater force of contraction
Explanation: Frank-Starling law: the more ventricular muscle is stretched by filling (preload), the greater the subsequent contraction force and stroke volume.
A single ECG cycle: the P wave marks atrial depolarisation (contraction signal), the large QRS complex marks ventricular depolarisation, and the T wave marks ventricular repolarisation (recovery) before the next cycle begins.
Concept context
Blood, lymph, the heart, the cardiac cycle, blood pressure, and ECG. High NEET weightage.