How does sugar enter neurons if they don't use insulin?

Question

I heard somewhere that as opposed to other cells, neurons do not use insulin to get their sugar supply.Why is that? What is the alternative mechanism? I assume sugar can't just enter the cell without some kind of help from a protein, is that true?

Answer 1

Hi Camren! So, I can’t exactly answer this question because the premise is incorrect. Insulin does not provide sugar to be used by cells. Insulin is a hormone secreted by the pancreas to encourage absorption of sugar/carbohydrates into the liver, fat and skeletal muscle cells as needed, and to help excess sugar be expelled via the excretory system. I know that sounds like I just contradicted myself, but here’s the tricky part- this sugar is not yet usable; the molecules are way too big! Insulin is also not the only hormone that guides sugar to cells. But once it is there, the sugar/carbohydrates need to be broken down through a process called glycolysis, which forms ATP, which is a unit of cell energy.

So if we rephrase your question to, “How do neurons obtain energy?”, I can tell you that neurons also use ATP, although it is not created by glycolysis, but by a chemical process created when the neurons fire. A more in-depth, but very readable, explanation of this process can be found here: http://mentalfloss.com/article/92939/whats-source-energy-powers-human-brain