Why hypocalcemia increases neuromuscular excitability and causes muscle tetany?

Hypocalcemia increases neuromuscular excitability because calcium ions play a crucial role in stabilizing the threshold potential of excitable membranes, including neurons and muscle cells. Low calcium levels decrease this stabilization, making it easier for action potentials to occur, which can lead to increased nerve and muscle activity. This heightened excitability can cause spontaneous muscle contractions and spasms, resulting in muscle tetany. Essentially, the lack of calcium disrupts the normal inhibitory effects on neuromuscular transmission, leading to excessive stimulation.