Question

The impulse of heartbeat originates from (a) SAN (b) \(\mathrm{AVN}\) (c) Vagus nerve (d) Cardiac nerve

Short answer

The correct answer is (a) SAN. The impulse of the heartbeat originates from the Sinoatrial Node (SAN), which is often referred to as the heart's natural pacemaker.

Step-by-step solution

Identifying the correct term

Begin by identifying which among the given choices is responsible for initiating the impulse of a heartbeat. It's important to note that this task requires familiarity and understanding of the cardiovascular system.

Confirming the answer

Ensure the selected answer is correct. The Sinoatrial Node (SAN) is responsible for initiating the impulse of a heartbeat. It's also known as the heart's natural pacemaker.

Key concepts

Sinoatrial Node (SAN)

Understanding the Sinoatrial Node (SAN) is fundamental in grasping how the heart beats. The SAN is located in the right atrium of the heart. Its primary role is to generate electrical impulses naturally, without the need for external stimuli. This characteristic qualifies it as the heart's natural pacemaker.

These impulses travel through the walls of the atria, leading to their contraction and pushing blood into the ventricles. This is what sets the rhythm of the heart, hence initiating each heartbeat. The SAN does this regularly, maintaining a consistent heart rate which can vary depending on the body's oxygen requirements.
Its unique properties include automaticity and rhythmicity, allowing it to function reliably over a lifetime without conscious control from individuals.

Heartbeat Impulse Initiation

Heartbeat impulse initiation is a critical phase of cardiac physiology, where the Sinoatrial Node (SAN) comes into play.

An electrical impulse is created when the cells of the SAN change electrically charged ions with the surrounding cells. This process is known as depolarization. Once generated, this impulse travels first through the atria, causing them to contract, and then moves to the Atrioventricular Node (AVN). From there, it passes down to the ventricles, ensuring proper blood circulation with a coordinated heartbeat.

Factors such as physical activity, stress, and various hormones can influence the rate of impulse initiation, leading to an increase or decrease in heart rate. It is this mechanism that was being tested in the exercise problem, identifying the SAN as the origin of the heartbeat impulse.

Cardiac Physiology

Cardiac physiology revolves around the study of the heart's functions and its vital role in circulating blood throughout the body. It includes understanding the structures involved, such as the heart muscle (myocardium), the chambers (atria and ventricles), and the electrical system that includes the SAN, AVN, bundle of His, and Purkinje fibers.

The smooth coordination of these elements ensures the delivery of oxygen-rich blood to the body and returns oxygen-poor blood to the lungs. The synchronization of the heart's mechanical activity with electrical signals is central to cardiac physiology. It's a complex symphony that is initiated by the SAN and depends on a fine balance of electrolytes, muscle cell contraction, and nervous system regulation.

In essence, cardiac physiology explains how electrical impulses translate into the physical beating of the heart, underlining the importance of correct impulse initiation for maintaining a healthy heart rhythm.