Question

Autorhythmicity is a special property of the muscles of the
(a) Liver
(b) Intestine
(c) Heart
(d) Kidney

Answer 1

Hint: The muscles of this organ are involuntary and they work on the excitation-contraction coupling mechanism in which the calcium ions that are released from the internal calcium store of the muscle cells play a crucial role.

Complete answer:
Autorhythmicity is the quality of generating its rhythm and is the property of the muscles of the heart that are called cardiac muscles. These are involuntary muscles with striated structure and found in the walls of the heart. These are also known as myocardium that constitutes the middle layer of the heart wall. Electrical stimulation in these muscles occurs in the form of an action potential that is induced by the pacemaker cells acting as a functional unit for the contraction of cardiac muscles. Due to the generation of an action potential, calcium ions are released from the sarcoplasmic reticulum which acts as the internal calcium store of these muscles. When there is a rise in the calcium level, myofilaments contract, and the mechanism is known as excitation-contraction coupling or calcium-induced calcium release. This mechanism is responsible for the auto-contraction and relaxation of cardiac muscles.
So, the correct answer is ‘Heart’.

Note: The main types of cells that provide the autorhythmic property to the heart are cells of SA node, AV node, and Purkinje fibers. A node sets the pace for the rest of the heart muscles and in this regard, it is known as the pacemaker of the heart while the excitatory cells constituting the fibers are responsible for the Autorhythmicity of heart.