Question

Which of the following statements is incorrect?

• A. SAN generates 70-75 action potentials per minute
• B. Cardiac cycle is 0.1 sec long
• C. Stroke volume is 70 mL
• D. Cardiac output is 5 L

Answer 1

The correct option is B Cardiac cycle is 0.1 sec long

Cardiac cycle consists of events that are cyclically repeated in a sequential manner. It consists of atrial and ventricular contractions and relaxations.The duration of the cardiac cycle is about 0.8 seconds.

SAN or the sino-atrial node is the natural pacemaker of the heart and it is capable of generating the action potentials. The rhythmic contractile activity of the heart is initiated by the SAN. SAN is able to generate about 70-75 action potentials per minute.

Stroke volume is the volume which is pumped out by each ventricle during a cardiac cycle. It is approximately equal to 70 mL of blood.

Cardiac output can be defined as the volume of blood which can be pumped out by each ventricle in a given time period (here, minute). Cardiac output is obtained when the stroke volume is multiplied by the number of heart beats per minute (heart rate). In a healthy individual, it is approximately equal to 5 litres of blood.