Read the following and choose the option with all incorrect statements.
(i) Heart is protected by a double walled membranous bag, pericardium enclosing the pericardial fluid.
(ii) The atrium and the ventricle of same side of heart are separated by thin fibrous tissue called atrio-ventricular septum.
(iii) The opening between the right atrium and the right ventricle is guarded by a valve formed by 3 muscular flaps or cups, the tricuspid valve.
(iv) Bicuspid valve also called mitral valve guard the opening between the left atrium and left ventricle of heart.
(v) The openings of the right and left ventricles into the pulmonary artery and the aorta respectively are provided with semicircular valves.
(vi) A specialized cardiac musculature called nodal tissue is distributed in the heart. A patch of this tissue present in right lower corner of right atrium is called SAN and that present in upper left corner of right atrium is called AVN.
(vii) The SAN can generate the maximum number of action potential, i.c., 70-75 min, and is responsible for initiating and maintaining the rhythmic contractile activity of heart. Therefore it is called the pacemaker.
(viii) The average heart beat per minute is 72.
(ix) The action potential generated by SAN which stimulate atrial diastole, increase the flow of blood into ventricles by about 30%.
(x) During ventricular diastole, the ventricular pressure falls causing the closure of semilunar valves which prevents the backflow of blood into the atria.
(xi) The sequential event in the heart which is cyclically repeated is called cardiac cycle.