Sudden decrease in serum calcium is associated with:: (A) Increased thyroxine and PTH secretion, (B) Increased phosphate, (C) Increased excitability of muscle and nerve, (D) Cardiac conduction abnormalities
Answer is C. C i.e. Increased excitability of muscle and nerve.A decrease in extracellular Ca2+ concentration increases the excitability of nerve and muscle cellsQ by decreasing the amount of depolarization necessary to initiate the changes in Nat K+ conductance that produces the action potential. An increase in Ca2+ concentration stabilizes the membrane by decreasing the excitability.Decreasing the external Na+ concentration decreases the size of action potentialQ but has little effect on RMP.Increasing the external K+ concentration decreases the RMPQ.