Extracellular calcium is the primary regulator of PTH secretion from the parathyroid gland. The fusion of secretory vesicles with the presynaptic plasma membrane.
<h3>What is meant by extracellular calcium?</h3>
Extracellular calcium is the primary regulator of PTH secretion from the parathyroid gland. In mammals and birds, the circulating levels of PTH are greatly altered by minute changes in the blood calcium concentration.
Even before calcium was identified as the trigger for exocytosis, reductions in extracellular calcium were known to increase the likelihood of action potential initiation (Frankenhaeuser and Hodgkin, 1957) by altering the properties of the neuronal ion channels.
Calcium from extracellular sources is necessary to maintain many cell types' metabolic processes. The calcium-sensing receptor (CaSR), which is located on the plasma membrane, allows cells to respond to these changes.
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