Which of the following is false about the left ventricle?

A. the same number of: Myocardial conducting cells do not have the same density of myofibrils as contractile cells. While they contain some contractile proteins, their primary function is impulse conduction rather than force generation, so their myofibril content is significantly lower.

B. fewer: Myocardial conducting cells, including those in the sinoatrial node, atrioventricular node, and Bundle of His, have fewer myofibrils compared to contractile cardiomyocytes. This structural adaptation allows them to focus on rapid generation and conduction of electrical impulses rather than strong contraction.

C. no: Conducting cells are not completely devoid of myofibrils. They retain some actin and myosin filaments, enabling minor contractile activity, but this is minimal compared to contractile myocardial cells.

D. more: Conducting cells do not require additional myofibrils, as their primary role is impulse initiation and propagation, not forceful contraction. Excess filaments would impede their conduction efficiency and slow electrical signal transmission.

Correct answer: Tachycardia

Tachycardia refers to a heart rate that exceeds the normal resting rate, typically defined as over 100 beats per minute in adults. It can originate from the atria, ventricles, or the sinoatrial (SA) node and may result from physiological responses such as exercise, stress, or fever, as well as pathological conditions including heart failure, anemia, or arrhythmias. Anatomically, tachycardia involves the conduction system of the heart including the SA node, atria, AV node, and ventricles, leading to faster depolarization and contraction.