Tag: cardiac cycle

The bundle of His is a collection of heart muscle cells, specialized for electrical conduction, that transmits the electrical impulses from the AV node (located between the atria and the ventricles) to the Purkinje fibers, which provide electrical conduction to the ventricles.

The Purkinje fibres are located in the inner ventricular walls of the heart, just beneath the endocardium in a space, called as the subendocardium. These fibres consist of specialized cardiomyocytes, that are able to conduct cardiac action potentials.

• The SA node is the heart's natural pacemaker. 
• The SA node is a muscular tissue where electrical impulses are generated for the rhythmic contractions of the heart.
  
  Hence, option D is correct.

Pulmonary circulation carries blood to and from the lungs. They include the pulmonary artery (aorta) and its branches to the capillaries in the lungs, as well as the veins, that drain those capillaries. The pulmonary arteries carry blood low in oxygen from the right ventricle, while the pulmonary veins carry blood high in oxygen from the lungs into the left atrium. This circuit functions to eliminate carbon dioxide from the blood and replenish its supply of oxygen.

Myogenic contraction refers to a contraction initiated by the myocyte cell itself.

The sinoatrial node (SAN) can generate the maximum number of action potentials, i.e., 70 - 75 beats/min, and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called as the pacemaker of the heart.

The Purkinje fibers are specialised conducting fibres present in the inner ventricular walls of the heart. They help in the contraction of the ventricles and thus maintain the rhythmicity of the heart.