Which of the following would cause the amount of oxygen released from oxyhemoglobin to be increased?

A. Endocardium: The endocardium is the inner endothelial lining of the heart chambers (endothelium + connective tissue), not cardiac muscle, so it does not contain intercalated discs.
B. Parietal pericardium: The parietal pericardium is the outer layer of the serous/fibrous sac surrounding the heart (protective membrane), not muscle tissue, so it lacks intercalated discs.
C. Epicardium: The epicardium (visceral layer of serous pericardium) covers the heart surface and contains connective tissue and fat; it overlies the myocardium but is not the muscle layer itself, so it does not have intercalated discs.
D. Myocardium: The myocardium is the heart’s muscular wall composed of cardiac muscle cells that are connected by intercalated discs (for electrical and mechanical coupling).

A. QRS complex: The QRS represents the rapid depolarization of the right and left ventricles (electrical activity that triggers ventricular contraction).
B. T wave: The T wave represents ventricular repolarization (the ventricles recovering electrically), not depolarization.
C. P wave: The P wave represents atrial depolarization, the electrical activation of the atria.
D. PQ segment: The PQ (PR) segment is the brief isoelectric period while the impulse travels through the AV node/AV bundle (a conduction delay), not ventricular depolarization.