Final answer:
Internodal delay in the heart's electrical conductance system allows for proper blood flow between atria and ventricles, represented by the PR interval on an ECG. Abnormal delays seen in this interval can indicate atrioventricular (AV) blocks of varying degrees.
Step-by-step explanation:
The purpose of internodal delay in the heart's electrical system is to allow time for the atria to contract and push blood into the ventricles before the ventricles themselves contract.
In an ECG trace, this delay is represented by the PR interval, which starts at the beginning of the P wave (atrial depolarization) and ends with the beginning of the QRS complex (ventricular depolarization).
Should there be a delay in the passage of electrical impulse from the SA node to the AV node, an abnormally long PR interval can be observed, which might indicate a first-degree AV block.
In more severe cases, where some or no impulses pass from the atria to the ventricles (second- and third-degree AV block, respectively), the ECG will show corresponding disruptions in the pattern of P waves and QRS complexes.