I think pretty much everyone has experienced the pins and needles feeling, but what is actually happening to cause this feeling? And what determines how long it will take for the “effects” to subside?
In: Biology
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It’s nerves getting squished, which confuses the message to the brain. That’s why we get the pins and needles; that’s literally your brain being confused and sending the wrong signals to your nerves.
Once the pressure on the nerve is released it goes back to normal.
If you think about it, it’s pretty clever. If we had no way of knowing when we’re doing damage to our nerves and no motivation to rectify the issue, we’d be pretty screwed.
What is happening when a body part falls asleep is for a period of time it has been robbed of oxygen in the form of blood. So the blood has been restricted, and the nerves are robbed of oxygen as a result.
The nerves don’t hurt while we’re sitting on the body part because there’s no oxygen/blood being sent to the nerves. Then when we stand up or move around, the oxygen/blood starts to go back to the nerves and “wakes” the nerves up. The feeling we perceive is the nerves waking back up because they have oxygen again.
You are experiencing a low grade neuropathy and the beginning of cell injury. Without blood flow and oxygen, tissues begin to die very quickly. When you restrict blood to your extremities, your nerves are some of the most delicate structures that begin to die first. Diabetes destroys your tiny blood vessels. This is why diabetics develop neuropathy in their feet (first) because it is the most dependent position furthest from your heart. Sitting on your foot or laying on your arm starves those issues of blood and oxygen, causes low grade damage. When you begin to move, the blood is quickly restored and no serious harm done. If you were to remain in that position long enough, or you weren’t able to move, such as large boulder on top of you, then you would likely have permanent cell death in that extremity.
Edit: This is also why we naturally toss and turn at night.
Your nerves are getting pinched and send random signals, kinda like static on a radio, that why it feels like a tingling
Blood has left the building (area that has pins and needles) and it took all the oxygen with it too. Now your nerves feel weird cos they really like oxygen.
Loss of blood flow- nerves in muscles deprived of oxygen cause pain as the muscle itself spasms
Anaesthetist here. One of our jobs is to look after the nerves of your body. If you are having a 4, 6 or 8 hour operation, you are going to be lying in one position for that whole time. If you happen to put pressure on a nerve for that time, you may compromise the blood supply to that nerve and cause permanent damage. We call this a neuropraxia.
The most common nerve for this to happen to is the ulnar nerve. It runs in a groove on the inside of your elbow. That’s the spot that really hurts when you hit your “funny bone”. If you are lying flat on your back and your palms are down (“pronated”), you will put pressure on your ulnar nerve at the elbow. So we make sure that when you are lying on your back, your palms are facing up (“supinated”). This position means your elbow is resting on the bone at the back (the “olecranon”) and not on your ulnar nerve. Try it for yourself.
This is just one of the many ways we look after the whole person during an anaesthetic.
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