Eli5 What happens during Hypo and hyperglycemia.

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Pretty simple quesrion, but undoubtably has a pretty conplex answer…
What actually happens to the body when we go into hypo or hyperglycemic shock?
I understand that diabetics have to watch their food consumption, and more accurately, their sugar consumption, because too much or too little causes us to go into hypo/hyperglycemic shock, but what happens?

In: Biology

The difference is actually simple: HYPOglycemia is too little blood sugar, HYPERglycemia is too much sugar. Sugar is where your cells get energy to function, so with too little, you just start powering down. With too much sugar, it can actually start bonding to random things in your blood stream, causing them to not function

Hyperglycaemia actually won’t cause too many problems immediately, it’s more of a long-term damage sort of thing–mainly, excess blood sugar damages blood vessels through mechanisms we still don’t fully understand, so you’re very prone to internal bleeding and strokes (this is actually what killed my sister). Hypoglycaemia, on the other hand, is highly dangerous because your cells need the sugar in the blood to function, and if blood sugar drops too low you can lose consciousness and die. This is why insulin-dependent diabetics generally carry some sort of sugary snack around with them that they can eat if they feel early symptoms of low blood sugar due to having taken too much insulin.

Insulin in the body works differently than in the brain. Insulin can become saturated while crossing the blood brain barrier (bbb) meaning the cells can’t transfer it from the body’s blood through the bbb and into the brain fast enough and it sits there.

Endocitosis saturation is like if you went to a shuttle bus to go to a concert and there were too many people for the bus and you had to wait longer for another bus. The insulin saturates these cells and over time, your brain begins to down regulate or make less of these busses because too many people (or insulin) is getting into the brain. So, over time the brain begins to stop making as many busses for the insulin because if it doesn’t make less, the bus drivers (endocytosis) will just keep making trip after trip as long as insulin er uh, people go to the bust stop.

Now after a long time the insulin has trouble getting into the brain when you eat a normal amount of sugar because you got rid of all the busses OR their eating habits are still bad and there’s still too much generally because sugar doesn’t need to take the bus. It has a vip pass and can directly cross the bbb, it never has to take the bus. This means the sugar/insulin balance in the brain is off balance

What does insulin do in the brain!? I’m glad you asked.

It regulates smells and tastes in the olfactory bulb and mouth.

It can indirectly stimulate the cranial nerves like the vagus or the trigeminal

It regulates feeding reward behaviors in the basal ganglia.

It regulates memories and plasticity in the hippocampus by changing the energy needed for brain cells to fire.

It does something different in almost every brain region and there’s only one or two regions in the brain that can make small amounts of insulin and it isn’t enough to properly regulate the entire brain.

Moral of the story, don’t eat 6 servings of grain a day.

Insulin acts kind of like a key that opens up the cell walls so that the glucose in your blood can get into the cells that they need to be in.

When there’s too much insulin in your body, your cells suck up every last bit of it and then there’s nothing left for the rest of your body (especially your brain) and you start getting weak and disoriented. That’s hypoglycaemia

When there’s not enough insulin in your body, then there aren’t enough keys to go around so the glucose stays in your blood and doesn’t get where it needs to be. As your blood flows through your body with all the extra sugar, it causes damage to areas with really tiny capillaries. When the blood gets to your kidneys, the kidneys see all the extra stuff and try to filter it out, which causes stress on the kidneys. That’s hyperglycaemia.

If you stay in hyperglycaemia too long, your cells still aren’t getting enough energy despite the excessive sugar. Then your body starts decomposing fat cells, which makes your blood acidic, and that’s called diabetic ketoacidosis

Hyperglycaemia is why diabetes tend to have lots of sugar in the urine. Before modern chemistry diabetes was diagnosed by “sweet urine”, for which the test was seeing if ants would be attracted to it.