Dear Jocelyn,

If you’ve ever had a leg or an arm “fall asleep,” the nerves in your brain and body were sending you an important message.

That’s what I found out from my friend Darrell Jackson, a researcher at Washington State University who studies how drugs affect the nervous system.

The nervous system is made up of bundles of nerve fibers that help humans think, feel and navigate the world. These nerves also help people sense things like temperature, vibrations, pressure and pain.

Darrell Jackson, a researcher and professor at WSU.

Jackson said you may feel pins and needles when your nerves get too compressed or squished down. We call this experience paresthesia (pear-ES-theesha).

It takes something called mechanical energy to compress the nerves. This energy might be the pressure from your head resting against your hand during a nap or the pressure on your legs while sitting crisscross applesauce.

When the nerves feel this pressure, they activate a kind of electrical energy. That’s right, you are full of electricity. The body and brain use electrochemical signals to send information to each other.

The nerves in your tingling leg, arm, foot or hand, can send information along your spinal cord which stretches from the lower back to the brainstem.

“From there, you are relaying the message from the spinal cord to an area of the brain called the diencephalon,” Jackson said.

The message continues on to a section of your brain called the somatosensory cortex. It’s here that you actually become aware, or perceive, that your leg is tingling or that your hand feels like it’s full of sand.

Darrell Jackson and students observe a brain.

“Once you get up and you start moving around, you’ll get information immediately,” Jackson said.

All of this information moves through the brain and body really fast—about 11,679 feet per second. That’s like running nine laps around a standard running track in a single second.

When the body senses this tingling pain, it activates another pathway in the body. The brainstem helps send information back down to the spinal cord to make the body less painful and less tingly.

If you compress your nerves for too long, it can damage your ability to sense the world. The pins-and-needles feeling can be a useful strategy to protect your nerves and keep you healthy.

ODr. Universe, a grey cat with a lab coat, in a hero poseur nerves are really important, and there are more than 7 trillion in the human body. Jackson reminded me our nerves not only help us sense pain but also play a big role in the reason why we have memories.

Jackson said one unsolved mystery about the brain is exactly how humans store their memories. Scientists are still really curious about it. But that’s a question for another time.

The next time you experience paresthesia, maybe you will remember something you learned from investigating this very question. Maybe you will take a moment to remember all the amazing things your body and brain do for you each day.

Dr. Universe




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