Body Fluids And Circulation

Question

The rhythmic heartbeat originates without external stimulation from a specialised mass of tissue in the right atrial wall; which structure functions as the natural pacemaker?

RankGuru · Accepted Answer

The human heart is myogenic, meaning the impulse for contraction arises within the cardiac muscle itself. NCERT Class 11, Chapter 18 (Body Fluids and Circulation) explains that a specialised mass of neuromuscular tissue, the sinoatrial node (SAN), is located in the upper right corner of the right atrium and generates the fastest spontaneous impulses, setting the heart rhythm. Because it discharges most frequently, the SAN is called the pacemaker. The atrioventricular node sits near the atrioventricular septum and relays the impulse from atria to ventricles, but its intrinsic rate is slower, so it does not normally set the pace. The bundle of His conducts the impulse from the AV node into the ventricular septum and is purely a conducting pathway. Purkinje fibres distribute the impulse through the ventricular walls, triggering coordinated ventricular contraction, again without initiating the beat. Thus the sinoatrial node is correct. A functional plausibility check confirms it: the pacemaker must be the tissue with the highest intrinsic firing frequency, and among the listed components only the SAN holds that role in a healthy heart.

Body Fluids And Circulation

Select the correct option:

🔒 Solution Hidden from View

More human physiology Practice Questions

In a standard electrocardiogram recorded from a healthy individual, the QRS complex of the tracing p...

Given that a heart ejects a stroke volume of 70 mL with each beat while beating 72 times every minut...

Following a carbohydrate-rich meal, blood glucose rises sharply; the pancreatic hormone secreted to ...

Inside red blood cells carbon dioxide is converted to bicarbonate, and chloride ions move inward to ...

According to the sliding filament theory of muscle contraction, the observable shortening of a sarco...

The resting neuronal membrane maintains a particular distribution of ions, being relatively impermea...

During the cross-bridge cycle in skeletal muscle, the regulatory protein that blocks myosin-binding ...

A fall in blood pressure within the afferent arteriole stimulates a specialised cellular complex of ...

A patient suffers from a progressive autoimmune disorder in which fatigue and weakness of skeletal m...

Considering that both kidneys together form filtrate at roughly 125 mL per minute, approximately wha...

At a chemical synapse between two neurons, transmission of the nerve impulse from one cell to the ne...

A deficiency in the secretion of a particular posterior pituitary hormone leads to the production of...

About This Question

Solution