Question

The nodal tissue located in the lower left corner of the right atrium is
A. SA node
B. AV node
C. AV bundle
D. Purkinje fibres

Answer 1

Hint: A heart node is a specialised form of tissue that functions as both nervous and muscle tissue. It induces nerve impulses, like nervous tissue that migrate across the heart wall as nodal tissue contracts, like muscle tissue.

Complete answer:
> In cardiac conduction, which is the electrical mechanism that drives the cardiac cycle, the heart has two nodes that are instrumental. These two nodes are the atrioventricular (AV) and the sinoatrial ( SA) node.
> AV node- The atrioventricular node is situated near the bottom of the right atrium, on the right side of the partition that separates the atrium. They are delayed for about a tenth of a second when the impulses produced by the SA node hit the AV node. This delay makes it possible to contract the atria, thereby emptying blood before ventricular contraction into the ventricles. The AV node then sends the impulses towards the ventricles down the atrioventricular bundle.
> SA node- The sinoatrial node coordinates heart contractions, also referred to as the heart's pacemaker. It causes nerve impulses that migrate across the heart wall, causing both atria to contract, located in the upper wall of the right atrium. The autonomic nerves of the peripheral nervous system control the SA node. Parasympathetic and sympathetic autonomic nerves transmit signals to the SA node, according to need, to either speed up or slow down the heart rate.
> AV bundle- Impulses are passed along to atrioventricular bundle fibres from the AV node. The atrioventricular bundle, also called the His bundle, is a bundle of fibres of the cardiac muscle found within the heart septum. This bundle of fibre stretches from the node of the AV and passes down the septum, separating the left and right ventricles.
> Purkinje fibres- Specialized fibre branches located just under the endocardium of the ventricle walls are Purkinje fibres. Such fibres stretch from the branches of the atrioventricular bundle to the left and right ventricles. Purkinje fibres easily transmit cardiac impulses to the ventricular myocardium, causing the two ventricles to contract.

Hence, the correct answer is (B).

Note: Normally, a specialised area of cells situated in the inferior-posterior region of the interatrial septum is the only direction available for the potential for action to enter the ventricles. The AV node is a highly specialised conducting tissue that considerably slows down the conduction of the impulse, providing enough time before ventricular depolarization and contraction for complete atrial depolarization and contraction.