16. Short answer questions VI

1. Why is the Sinoatrial node called the pacemaker of heart?

 

a. The contraction of the heart is initiated by the .

 

b. SA node is a mass of  tissue, and is made up of thin fibres.

 

c. SA node acts as a  of the heart or 'Heart of heart' as it initiates impulses that stimulate the  of heart muscles.

 

2. Differentiate between systemic circulation and pulmonary circulation.

 

a. In  circulation, the flow of oxygenated blood from the  ventricle to the various parts of the body and the return of deoxygenated blood to the right atrium occurs.

 

b. Systemic circulation carries  to the tissues of the body and also removes \(CO_2\) from the tissues. The  carries oxygenated blood to all the organs of the body.

 

c. In  circulation, flow of deoxygenated blood from the right ventricle to the lungs and the return of oxygenated blood from the lungs to the left atrium occurs.

 

d. Pulmonary circulation starts in the  ventricle. The pulmonary artery emerges from the right ventricle and reaches the lungs with  blood.

 

e. Pulmonary veins collect  blood from the lungs and supply it to the left atrium of the heart.