Subject Experts Solutions for Exercise 4: ASSERTION & REASON CORNER

Assertion: There is no mixing of oxygenated and deoxygenated blood in the human heart.

Reason: Valves are present in the heart which allows the movement of blood in one direction only.

Assertion: Left atrium has the thickest muscles.
Reason: Right atrium receives blood from the lungs.

Assertion: Sino-atrial node (SAN) is called the pacemaker.

Reason: SAN generates the maximum number of action potentials and is responsible for initiating and maintaining the rhythmic contractions of the heart.

Assertion: Atria act as primer pumps that increase the ventricular pumping.

Reason: About 80 percent of the blood flows directly through the atria into ventricles.

Assertion: There are $72-75$ heart beats per minute on an average when a person is performing normal work.

Reason: One heartbeat is completed in 0.8 second.

Assertion: The cardiac output of an ordinary man and of an athlete is the same.

Reason: It is impossible to alter the stroke volume as well as heart rate.

Assertion: The enlarged Q and R waves indicate myocardial infarction.

Reason: Any deviation in the normal recording of ECG indicates possible abnormality or disease.

Assertion: Neural signals through sympathetic nerves can increase the strength of ventricular contraction.
Reason: Parasympathetic neural signals synergistically act with sympathetic neural signal to increase the cardiac output.