Beginning of ventricular systole 7. ventricular relaxation D. 3, 5, 6, 1, 8, 4,

Question

Beginning of ventricular systole 7. ventricular relaxation D. 3, 5, 6, 1, 8, 4, 2,7 E. 3, 2, 6, 4, 5, 8,7,1 1 8. ventricular ejection 22. Lobsters have_ hearts. A. myogenic B. neurogenic C. hemogenic D. plyogenic E. noninnervated . Each cardiac cycle of a mammalian heart is initiated by: A. depolarization of the AV node myocytes. B. depolari zation of AV node sympathetic nerve cells. C. depolarization of SA node sympathetic nerve cells. D. depolarization of the SA node myocytes. E. the medullary cardiovascular control center of the brain. ?. At an intercalated disc of a vertebrate heart: A. two cardiac muscle cells are connected by gap junctions. B. the cell membranes of two cardiac muscle fibers are completely separated by a synapse. C. the myofibrils are loosely attached to the membrane of the disc. D. t-tubules unite the membranes of the adjoining cells. E. All of the answers are correct.

Explanation / Answer

D. Depolarisation of SA node.

SA node is called pacemaker of the heart. it initiates carfiac impulse at rate of 72 times per minutes that causes contraction of cardiac muscle.

A two caridac muscles are linked at gap junctions. These gap junctions are source of communication between two cardiac muscles for synchronised cardiac contraction.

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