Hypocalcemia is characterized by all EXCEPT:
Correct Answer: Shoening of Q-T interval in ECG
Description: Plasma Ca++ stabilizes membrane potentials. Hence, hypocalcemia may lead to various manifestations of increased membrane excitability. For nerve and muscles, their threshold comes closer to RMP. Spontaneous APs are fired in the nerves. The hyperirritability of the motor nerves and the innervated muscles leads to the symptoms of "tetany". Carpopedal spasm: may occur spontaneously or by inflation of BP cuff applied to arm - Trousseau's sign. Tapping of facial nerve over the angle of mandible causes unilateral spasm of facial muscles - Chvostek's sign. Laryngeal stridor or laryngeal spasm. Death may occur from asphyxia. Tendon reflexes - hyperactive. ECG changes: Prolongation of the ST segment and consequently QT interval. Reason: Low serum Ca++ decreases K+ permeability, lengthens phase 2 (plateau) of the AP, and slows the rate of repolarization, thereby prolonging the Q-T interval. Thus, option C is an incorrect statement, hence the answer. There is tingling and numbness of the extremities; in the circumoral region it may be a rare manifestation.
Category:
Physiology
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