18. Which is CORRECT about the heart? A The left side of the heart is part of th

Question

18. Which is CORRECT about the heart? A The left side of the heart is part of the pulmonary circuit of ciroulation B. The pulmonary trunk is a vein C. T he coronary circulation supplies blood to the heart D. The puimonary veins take blood to the lungs E. All of the above. 19. Which best descibes the function of the absolute refractory period in the cardiac action potential? A It is a period when the heart if stimulated may produce a stronger contraction. B. It is a period when tension develops in the myocardium but the muscle does not contract C. It is a period when the heart if stimulated will not produce another action potential. D. It is a period when calcium entering is balanced with potassium leaving producing the plateau phase. E. None of the above. 20. Which is CORRECT about the heart? A The bicuspid valve separates the right atrium from the right ventricle. B. Contraction of the papillary muscles closes the atrioventricular valves. C. The pulmonary artery contains oxygenated blood. D. The left ventricle is thicker than the right ventricle E. All of the above. 2Which is a difference between cardiac and skeletal muscle? B. Cardiac muscle cells are branched. A. Cardiac muscle has sarcomeres C. The ventricular cardiac action potential is completed before tension develops. E. None of the above. D Cardiac muscle cells have a sarcolemma. Which is CORRECT about the ventricular cardiac action potential? A. Repolarization is due to the efflux of potassium ions. B. The plateau phase is due to both calcium and potassium ions C. Depolarization is due to the influx of sodium ions. D. All of the above. E. None of the above. 23. Which is CORRECT about the pacemaker of the heart? A. There is no resting membrane potential of the sinoatrial node cells. B. Automaticity occurs due to the opening of sodium channels that open at hyperpolarizing potentials. C. Sinoatrial action potentials are due to voltage gated calcium channels D. Repolarization is due to opening of voltage gated potassium channels. E. All of the above.

Explanation / Answer

18. The right side of the heart is a part of the pulmonary circulation. The pulmonary trunk is not a vein rather an artery. The two main coronary blood vessels branch off into smaller arteries which supply oxygen rich blood to the heart muscles. The pulmonary veins carry oxygen rich blood from the lungs back to the left atrium of the heart. Hence, option C is the correct answer.

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