i. Results from activity of membrane wa+ - x+ ATPase.

ii. Automaticity of pacemaker cells increases after these cells are excited at a
higher frequency.

11. When an ectopic focus in atria with higher rate than SAN stops firing suddenly
SAN will remain quiscent for some time due to overdrive supression.

iv. Results from activity of ca2+ ATPase pump.

A:-Only i and iii
B:-Only i and ii
C:-Only iii and iv
D:-Only i, ii and iii
Correct Answer:- Option-A
Question47:-Which of the following statement is/are true about second heart sound

?

i. ls composed of higher frequency vibrations is of short duration and lower
intensity than first heart sound.

ii. Portion of second heart sound caused by pulmonic valve closure is heard best at
second thoracic interspace just to the left of sternum.

iii. The aortic valve sound is generally louder than pulmonic.

iv. The nature of second heart sound changes with respiration

A:-Only i and iv
B:-Only i, iii, iv

D:-All the above i, ii, iii, iv
Correct Answer:- Option-D

Question48:-Which of the following statement is/are true about atrial systole ?

i. Contribution of atrial systole to ventricular filling is governed to a greater extent
by heart rate and position of AV valve.

ii. Onset of atrial systole occurs with beginning of 'P' wave of ECG.

iii. Atrial systole is responsible for small increase in atrial, ventricular and venous
pressures.

iv. Transfer of blood from atria to ventricle by atrial contraction completes the
period of ventricular filling.

A:-Only i, ii and iii
B:-Only i, ii and iv
C:-Only i, iii and iv

Correct Answer:- Option-C
Question49:-Which of the following statement is/are true about cardiac innervation
?
i. Administration of atropine can increase heart rate from normal resting rate to
150-180 beats/mt.
ii. Increase in force of contraction of heart on sympathetic stimulation is inotropic
effect.
iii. In humans in whom both nor adrenergic and cholinergic systems are blocked,