What causes body parts to fall asleep?

Question

Throughout my life, I've had body parts fall asleep (mostly my feet). I get a weird sensation called Paresthesia, or "pins and needles". Though it goes away after a some time, I hate the several minutes that I do have because it is very uncomfortable. I always thought they were caused by just inactivity, but I realized that I've had lots of times when my feet have been inactive for hours (mostly when I'm sleeping, but a lot of times when I'm working too) but I never get pins and needles.

So my question is, What causes body parts to fall asleep?

Answer 1

Paresthesia can be caused by inactivity, sustained pressure on the nerve, neurological disorder, or nerve damage.

If the causes is from pressure, the user V_ix on Biology gave the following answer here which I have quoted:

Underneath the superficial layers of your skin there are receptors which sense pressure, temperature and pain. These receptors are part of the peripheral nervous system which senses stimuli and they take the message conveying details about the stimulus to the somatosensory cortex of the brain. Here is where the perception of pain, burning, pressure etc is ultimately made. To take the simplest example, if you stop blood flow for a short amount of time in a limb, these receptors are activated, and will send signals to the brain that are interpreted as tingling or numbness. With more severe pain, different receptors are activated which , again, project to the same brain area but a different message is read out. If the pressure from one limb is removed, the receptors will go back to normal function as blood flow is restored.

If what you experience is chronic, you may need to see your healthcare provider in order to rule out a neurological disorder or nerve damage. You can find more information on paresthesia from the National Institute of Neurological Disorders and Stroke as well as clinical trials if you are really concerned about this on their site:

• http://www.ninds.nih.gov/disorders/paresthesia/paresthesia.htm

Answer 2

While dustin has explained it in a modern way, I'll have my two cents talking about this problem in Ayurveda, the traditional Indian medicine.

Ayurveda describes that there is a poor blood circulation and vitiation of vata dosha. The body cells require oxygen constantly, and in certain quantity. For some or the other reason, if they don't get sufficient 'food' (i.e. oxygen), they start behaving abnormally and one of their characteristic of being abnormal is causing weakness, tingling or emptiness. Modern science considers 'neuropathy' as one of the causes and in most of the cases, the patients are prescribed with vitamin pills especially containing methylcobalamin.

But in Ayurveda, improving blood circulation (and so taking oxygen to every peripheral tissue) comes with good massage. The therapy can be augmented with medicated oil that has anti-vata properties. Some physiotherapy, massage, yoga etc. can help you get rid of this problem. Take a note that alternative medicines are never considered as a first line treatment. That's why they are alternative. So, what I suggested is beneficial in reducing/preventing it but it's not the primary treatment.