eli5: Why does your hand/body part go numb when you lay on it for too long?

Question

As the title says. From what I understand, it has to do with cutting off circulation, but why does that affect your sense of feeling in your hand?

In: Biology

Answer 1

The blood carries nutrients all the cells in that limb, which includes nerve cells. When you cut off circulation for a bit of time, the nerve cells begin to shut down and eventually die. During this shutdown phase, they are unable to send and receive signals, which is why you lose your sense of touch, temperature, and the area goes numb. When you reintroduce blood to the area, the nerves can then send the “something’s wrong” signal, which is the pins and needles sensation you get.