Question

The given figure illustrates a section through the human heart. Which labelled part represents the site for the generation of action potential in the human heart?
a. A
b. B
c. C
d. D

Answer 1

The human heart is responsible for maintaining a number of different functions such as pumping of blood to different parts of the body in a rhythmic manner. The blood contains and transports gases, nutrients and hormones which are sent to reach every tissue due to the action of the heart.

Complete answer:
The heart is a muscular structure. In humans, the heart is divided into four chambers which are upper left and right atria and lower left and right ventricles. The atrium and ventricle of the right side are known as the right heart and the left atrium and ventricle is known as left ventricle.

The pumping action of the heart takes place in a rhythmic manner. The process of the rhythm is determined by the group of cells present in the upper right atrium corner as the sinoatrial node or SA node. This generates a current which is known as the action potential and it causes contraction of the heart.

Action potential can be described as a rapid change in the membrane potential which is produced by the movement of the charged ions. When there is no stimulation, the non-pacemaker cells which are the ventricular and atrial cells are maintained at a constant membrane potential. This constant potential is known as resting potential.

The sinoatrial node (SA node) is a group of cells that are responsible for generation of current in the form of action potential. These cells produce an electrical stimulus which travels through the heart via the electrical conduction system and results in the contraction of the heart. The SA node continuously works to generate action potential and helps to set the rhythmic condition of the heart. Due to this reason, the SA node is also referred to as the pacemaker of the heart.

Hence, the correct answer is option (B).

Additional information:
- B represents a tricuspid valve which is made up of three flaps which allows the blood to flow from right atrium to the right ventricle and prevents backflow of blood.
- C denotes the right ventricle which receives deoxygenated blood from the right atrium and pumps it to the pulmonary circulation.
- D is the atrioventricular or mitral valve which separates the atrium and ventricle of the left side.

Note: The pumping of the blood to different parts of the body is an important function of the heart. The rhythmic contraction of the heart is brought about by generation of electrical stimulation which is known as the action potential by the sinoatrial node or SA node. It is also known as the natural pacemaker of the heart.