Why the cardiac impulse does not generate if SA node becomes defective?

Why do cardiac muscles never get fatigued?

Function of SA node is

A : The cardiac impulse which originates from SA node in mammalian heart cannot spread directly from atria to ventricles R : In mammalian heart there is no continuity between cardiac muscle fibres of atria and those of ventricles except AV bundles.

How is a cardiac impulse, conducted in heart?

Why is friction generated?

Where does cardiac impulse originate. How is it conducted to the rest of the chambers.

The impulse which generated in SA node suddenly fails to be transmitted in both ventricles than –

Assertion : Though AV node generates impulses, it is still not called as the pacemaker of heart. Reason : The rythmicity of impulse production is not highest in AV node in the neuromuscular conduction pathway.

Go through the following statements (i) Vagus nerve decreases the rate of impulse formation from the SA node and its conduction (ii) As the human heart is myogenic in nature, the rate of formation and conduction of cariac impulse cannot be changed by the action of nerves (iii) The end of T-wave in ECG marks the end of systole. (iv) If the P-wave in ECG is inverted , it indicates that SA node fails to initiate impulse and the atrial muscle depolarises by the impulse originating in A.V. node. Whic of these are correct ?

Assertion : The cardiac impulse is said to be myogenic. Reasoning : The rate of formation and conduction of cardiac impulse can be changed by the action of nerves.