Good morning, John.

PAIN!

Today is inspired by a comment on John's video about me needing to be punished. I am going to talk about the science of pain, while experiencing pain.

Let's start out with pain that is detected by the systems designed to detect pain.
[SLAP]
This is called nociceptive pain. It's the kind of pain that we need, something bad is happening, and so our brain is like "THIS IS UNPLEASANT, RUN AWAY!"
There are three different kinds of nociceptive pain, first superficial somatic nociceptive pain. This is basically skin-based pain. We have TONS of pain receptors in our skin because it's our first line of defense, so we need to gather a lot of information.
When I get whipped, my skin can feel every single lash of the whip as a separate pain. 

Deep somatic pain, on the other hand, is what we feel when our muscles are burning and when we have to strain or a sprain or a broken bone. It's a less specific pain, but it can extremely intense.

This is a weird kind of pain test, right now my muscles are undergoing anaerobic glycolysis, which is increasing the acidity of my muscles. Neurons are detecting that increase in acidity and relaying that signal to my brain as pain. And, WOW, WOW, that's painful!

ARRRRGH!

The final type of nociceptive pain is visceral pain. This is usually pretty vague and distant, but can also be very intense. For women, think of cramps. For guys, think of testicular injuries. I'm not going to demonstrate this; it would be dangerous.

Now in addition to nociceptive pain, the other kind of common pain is neuropathic pain, when your nerves are damaged or malfunction and send pain signals when they shouldn't. One of the only big nerves that runs close to the surface of the skin is right here, your ulnar nerve, and if you whack it OOOOWWWWWW I did it aaaah I achieved - goal accomplished!

Funny bone... that's, that's your neuropathic pain. I didn't think I was going to do it so good.

Referred pain, on the other hand, is when the source of the pain gets mixed up by your nervous system. Yes there's a stimulus, but no it is not being received in the right place.

AAAAAAAAAAAAA OWWW!

My eyes were watering!

Oh good thank God I was recording; I thought I wasn't recording for a second.

And your nociceptive pain system can also be tricked and to understand this we kind of have to understand how the entire nervous system works. Cells that detect sensation, whether that's pain or light or smell, they all kind of work the same way. They spend almost all their time maintaining an ion gradient across the membrane of the cell, so there's a different charge inside the cell than outside. They also, on the surface of the cells, have these channels that when opened, equalize that ion gradient, so they become neutrons. And at the surface of those channels, there's a protein that's designed to open the channel when a specific thing happens. That circumstance can be the presence of salt or heat or sound or light. This is how we detect everything. All of our sensations. But sometimes, circumstances
that these surface proteins weren't designed to respond to nevertheless activate them. 

For example, there is a protein called TPRV1 that's designed to open a channel in response to heat, acidity, or abrasion. But it also, just by chance, opens in the presence of a molecule called 
capsaicin. Capsaicin is entirely harmless, it does no damage to your skin, but it does open that channel so it is detected by your brain as pain. And capsaicin is the chemical that makes chili peppers hot.

OOOH. AAAALALALA

The burning that I'm experiencing right now has nothing to do actual damage inside of my mouth. It is purely a biological accident, and my body does not believe it!

Now, pain is an important system. We live inside of our bodies; we would be nothing without them, so we have to protect them. People who are born without the ability to sense pain often die before adulthood.

But it's not like a super well designed system or anything. It's extremely old. It's a holdover from ages and ages of evolution ago. It leaves a lot of opportunities for things to go wrong, and so many people have to deal with chronic pain that is extremely difficult to manage. But for most of us, though inelegant and unpleasant, pain is, oddly enough, something we should be thankful for.

John, I'll see you on Tuesday.

Today is inspired by a comment on John's video about me needing to be punished. I am going to talpahbababalablahaha lalala. Me needing to be plalalalala. Me needing to be- me needing to be memeneeding beebee. Tahmah needibala la la LA la la. Oh my god it got so- first sentence of the video.

Doesn't hurt, that doesn't hurt, that hurt.

Lindsey: I don't know about this!

Hank: You can do it! AAAAAAH!!!

Lindsey: I'm so sorry!

Hank: No it wasn't that bad.

[singing] Denver the last dinosaur, he's my friend and a whole lot more.