Which organ is important as a large reservoir of erythrocytes?

If the heart of a mammal is injected with a $2\%$ $CaCl_2$ solution,then:

Which organ is supplied with blood by the coronary artery?

The correct pathway of the impulse of heartbeat through the heart is ...........

What is the cardiac output produced by a normal heart?

In the heart, as the action potential reaches the $AV$ node from the $SA$ node, there is a delay of the action potential. This delay is important because: