Topic: Pins and needles. Why do limbs fall asleep? Because they are tired. No. It basically happens because of nerves. Through nerves, our brain communicates with our limbs. Wow. Nerves are so amazing. Yes. However, when we cross our legs or sleep on an arm for very long, we apply pressure causing the nerve pathways and its surrounding arteries to squeeze. Hence, the nerves do not work properly and the arteries cannot supply required nutrients to the nerves. As a result, the signals sent by our brain
do not reach the limb. Thus, we cannot move it. So, we say that our limb has fallen asleep. Also, in some situations, some of these squeezed nerves stop sending signals while some fire hyperactively. This gives us the sensation of pins and needles.