Exocytosis and increased intracellular Na

Exocytosis, which occurs when intracellular vesicles fuse with the plasma membrane, provides a route by which membrane-impermeable molecules synthesized by cells, such as proteins, can be released into the extracellular fluid.  Moreover, it provides a way to replace portions of the plasma membrane that have been removed by endocytosis, and in the process, to add new membrane components.  The secretion of substances by exocytosis can often be triggered by stimuli to the cell that lead to an increase in cytosolic calcium concentration, a processes known as regulatory secretion.  This enables a cell to respond rapidly after the arrival of the stimulus.

Hello bioman,

I am well aware of this concept. But what exactly is the answer here? Depolarization or regulatory secretion? The mechanism that leads to a rise in an intracellular Na+ concentration is depolarization, but this also leads to the influx of Ca2+ from the extracellular milieu and consequently neurotransmitter or hormone release. When they ask for the mechanism, is what I wrote right? Or are they asking for a specific title of this mechanism? =/

Hi Ehd123, I thought the last part of the paragraph I provided answered the question, this part:

The secretion of substances by exocytosis can often be triggered by stimuli to the cell that lead to an increase in cytosolic calcium concentration, a processes known as regulatory secretion.  This enables a cell to respond rapidly after the arrival of the stimulus.