Hypoglycemia (Low blood sugar) is said to be among the potential causes of human-faintings. I was wondering by which mechanism does this happen. Google search results are abundant, there are lists of various causes and solutions, but I couldn't find a direct answer to my question.
Is it a controlled reduction of heart function to save energy? Is it an uncontrolled shock reaction (malfunction)? I'm looking for an answer along those lines.