A Certain Scientific Railgun- Misaka Mikoto the walking stun gun
Misaka Mikoto level 5 electromaster, and the resident bug zapper of Academy City is the lead heroine of her own story in A Certain Scientific Railgun, a spinoff of A Certain Magical Index. As a master of electromagnetism, Misaka Mikoto has a wide range of powers, from clinging to metal structures using magnetism, to firing off lightning bolts, manipulating metals, hacking computers, to firing off her signature railgun. In episode 23 of the second season we see another novel use of her powers.
As amusing as the walking stun gun is, how does it work and how much real world science is involved? The result might just surprise you.
Before we begin to ponder how the walking stun gun works, let’s consider how Misaka Mikoto ended up in a situation where she had to consider a novel use for her abilities. During the course of the Silent Party arc Misaka Mikoto ends up injected with a drug that blocks the transmission of commands to the nervous system, or at least that is how Nunotaba Shinobu explains it.
Let me begin to explain to you how Shinobu’s explanation is wrong. First off, the drug could not have completely blocked all commands from the nervous system to the rest of the body, otherwise Misaka Mikoto would not have been able to breathe, let alone talk. Second, such a drug could not have been administered through an injection in the arm.
If you wanted to paralyze someone from the neck down, you would need to use a spinal block. A spinal block injects anesthesia into a part of the spinal column which blocks the sensation and muscle movement from the point of injection and below. This is sometimes used for women in labor instead of an epidural. While it is possible to perform a spinal block in the neck, blocking all sensation and motor control, it is more complicated due to the size and number of structures in the neck.
Thus, I am going to call the injection that incapacitates Misaka busted.
In a previous post I discussed how the nervous system runs on electrical impulses called action potentials. These action potentials are how neurons communicate with each other and other tissues of the body including muscles. When the nerve impulse reaches the muscle, it comes to a structure called the neuromuscular junction.
The electrical impulse causes the end of the nerve cell (terminal button) to release acetylcholine (a neurotransmitter), which travels across the small open space (synaptic cleft), causing a change on the surface of the muscle cell (sarcoplasm). The end result of this change is that another nerve impulse (action potential) travels across the muscle cell, causing it to contract.
External stimulation of muscle fibers
It has actually been known for some time that muscle fibers run on electrical impulses, dating all the way back to Luigi Aloisio Galvani (1737-1798), who did the famous frog leg experiment. Gentlemen, a word to the wise, I do not recommend reproducing the experiment as a prank, the ladies will not appreciate it.
But does it work on humans? The answer to that question is yes, and no. You can’t just hook up a bunch of random electrodes to your skin and expect them to work, but electrical muscle stimulation (EMS) is a thing, and it does have its uses, but these are not full contractions like what you would see when extending your leg.
First off, human skin has some resistance to electricity and the electrical current is not large in order to prevent injury. When done right, it will feel like the muscle is twitching a little, kind of like an eye twitch but in the targeted area. The main use of EMS is for physical therapy, weight loss, and strength training. I had EMS once or twice back in high school, but I don’t remember if it did much of anything at the time, but I know it is a valid tool in the therapist’s toolkit. It is mainly used to help prevent muscle atrophy in cases of disuse, like coma patients. In fact it is briefly mentioned in the SAO novels as one of the reasons Kirito and the other SAO survivors are able to move somewhat after essentially being in comas for three years. The electrical stimulation would have given their muscles some degree of activity, reducing the damage from being bedridden for so long. The next use is for weight loss, where the small muscle contractions caused by the EMS device is said to dramatically increase the number of calories you will burn in a single day. Now despite what all of the slick commercials will tell you, EMS devices have almost no effect in terms of increasing the number of calories you will burn in a single day. The last use is for various types of strength training, and while one or two studies might have shown a very small improvement, none of these studies have been reproduced, so again you are looking at modern day snake oil.
Wait, didn’t you just say that electrical impulses can cause muscle movements? I did and they can, you just need to provide a lot more power than EMS devices can. High levels of electricity can cause the muscles of the human body to completely contract in convulsions. A stun gun can cause this to happen and that uses 50,000 volts compared to the 70 millivolts found in an action potential. Not to mention that this is extremely painful and the voltage can be so high that it actually causes the muscles to cease functioning all together for a short period of time. As you can imagine, Misaka Mikoto is not having a good day when she first tries to use her own electrical powers to remote control her muscles.
Shinobu even points this out as Misaka Mikoto begins to sit up. When it comes to cells that interact with electricity, the cells need a chance to reset after each electrical impulse. This is due to the change in the ion concentrations both inside and outside of the cell after each impulse. These reset periods vary by cell type, but they are all very short. The problem with large amounts of electricity is that these cells then need a longer period of time to reset back to normal, which explains her sitting still for a few movements once she is up off the table. She overdid it on the first try and needs to let her muscle cells reset.
At this point I’ll chalk it up to Misaka Mikoto being a genius as to how she is able to walk out of there without having to stop after each step. She probably was able to figure out how to channel just the right amount of electricity to each muscle needed to move without causing the muscles to seize up or cause extreme amounts of pain. This more direct stimulation of the muscles would dramatically reduce the amount of electrical power needed and increase her ability to move in a coordinated manner. This of course would reduce the possibility of her stunning Kuruko when the crazy teleporter tried to hug her, but it makes for a funny scene, and Kuruko being shocked is always a good thing. This means that while she could use her powers to move again, she wouldn’t be a walking talking stun gun.
As crazy and fantastical as all of this sounds, modern medical technology is in the process of recreating what Misaka Mikoto did during the scene. The device is called a neural bridge and it reconnects severed nerves by acting as a bridge over the damaged segment.
The device is simple in theory, but complex in its actual execution. In the test case the individual damaged his spine at the C5 vertebrae, which impaired his ability to move his arms and legs. The patient’s brain still worked fine and could send commands to move the muscles in his limbs, but the messages couldn’t get around the damaged area. This is where the device comes in, by using a series of electrodes and electrical stimulation to retrain the brain to use undamaged areas of the spinal cord. This reroutes the messages through undamaged areas, allowing the patient to regain some function. While it did not restore full function to the patient’s limbs, it did restore enough ability for him to function normally in society.
Another new technology to bypass damaged nerves involves the use of brain implants. In this case a microchip is implanted into the motor cortex of the patient’s brain, which is the area of the brain that controls movement. The computer chip then sends signals to an EMS device that can precisely stimulate various muscles. By using complex computer programs the device allows the patient to regain control of their hand which was immobilized by a nerve injury.
It should come as no surprise that I am going to call all aspects of the walking stun gun scene busted.
That being said, of course I still think it is a cool scene and it fits in the science is magic setting of A Certain Scientific Railgun. I also find it very interesting that medicine is using new breakthroughs in technology to allow people to remote control their own muscles to bypass damaged nerves, much in the same way that Misaka Mikoto did, just without the ESPER powers.