Final answer:
Low serum calcium increases nerve excitability by enhancing sodium ion permeability, leading to a lower threshold for action potentials and resulting in spontaneous muscle contractions.
Step-by-step explanation:
Spontaneous muscle contractions (fasciculations) caused by low serum calcium concentration result from a lowered threshold for nerve action potentials. This is due to increased permeability of nerve membranes to sodium ions when serum calcium is low which makes neurons more likely to fire. This increased excitability can lead to spontaneous depolarization and muscle contractions. Essential elements such as excitation-contraction coupling, the role of calcium ions, and the sliding filament model of muscle contraction illustrate how muscle fibers contract and how altering calcium levels can affect this process.
Spontaneous muscle contractions (fasciculations) caused by low serum calcium concentration result from a lowered threshold for nerve action. When there is low serum calcium, it increases the permeability of the muscle cell membrane to sodium ions, resulting in an increased excitability of the nerve fibers and a lowered threshold for nerve action. This leads to spontaneous muscle contractions or fasciculations.