MEDICAL PHYSIOLOGY

Detailed explanation-1: -The sinus node continuously generates electrical impulses, thereby setting the normal rhythm and rate in a healthy heart. Hence, the SA node is referred to as the natural pacemaker of the heart.

Detailed explanation-2: -Final answer: The rhythmic contraction and relaxation of the heart muscles is initiated by a tissue called Sinoatrial node.

Detailed explanation-3: -The SA node comprises specialized cells that undergo spontaneous generation of action potentials at a rate of 100-110 action potentials ("beats") per minute. This intrinsic rhythm is strongly influenced by autonomic nerves, with the vagus nerve being dominant over sympathetic influences at rest.

Detailed explanation-4: -Sinus Rhythm originates from the SA Node (Sinoatrial Node) which initiates each heartbeat. The electrical impulse originating in the SA Node travels across the atria, causing atrial depolarization, and can be seen as a P wave on the ECG tracing.