In $\text{ECG}$,the $\text{QRS}$ complex represents:

Which wave is produced when the action potential is conducted from the $AV$ node to the Purkinje fibers?

In all the leads of $ECG$,all following are positive waves except

Complete the missing words in the statements given below:
$(a)$ Plasma without clotting factors is called serum.
$(b)$ $.........$ and monocytes are phagocytic cells.
$(c)$ Eosinophils are associated with $.........$ reactions.
$(d)$ $.........$ ions play a significant role in clotting.
$(e)$ One can determine the heart beat rate by counting the number of $.........$ in an $ECG$.

Systolic pressure is higher than diastolic pressure because

Describe in detail: $ECG$.