Radio sucks. Ergo, it got stuck on Tammy Bruce during my iced tea run. She was going on about how the guy who woke up from the coma changes everything about the Schiavo situation. I was going on about how she’s a stupid [censored]. Apparently the conservative world needs a quick lesson in neurobiology. So here we go.

This is a nerve cell (neuron):

(from http://faculty.washington.edu/chudler/color/pic1.html)

Notice that there’s a big fat part at the top. That’s the cell body. That’s where all the machinery that makes the cell do its thing is. That’s where the DNA, the mitochondria, the ribosomes, all of that are. These provide the instruction set, energy, and proteins, respectively.

Now the long part is called the axon. It’s basically a biological combination of an electrical conduit and a subway tunnel. It’s essentially a passive structure. Nothing starts in the axon, merely passes through it.

At the end are the synaptic terminals. This is how the nerve cell sends a message to the next nerve cell in the chain.

Looking back to the top of our picture, the yellow branch-looking thingies are what receive the signals sent by the synaptic terminals.

Ok, now that we know all about that we can discuss how nerves respond to injury. Nerve cells, along with muscle cells, don’t keep proliferating and dividing in adulthood. They’re done. This is why after a heart attack you have reduced heart function. Once those cells die from lack of oxygen, nothing can grow back to replace them. This is also why in stroke patients, even after they recover function, it’s rarely as good or as natural-feeling as it used to be. The injured area doesn’t regenerate, other cells just learn to pick up the load.

But while we can’t make new nerve cells, injured nerve cells can regenerate. This is why finger re-attachments work. They can even take the relatively useless sensory nerves that pass over your collar bone and put them into your face to replace damaged or congenitally absent nerves there.

It’s important to note that a neuron can only regenerate if its body is intact. As I mentioned, all the machinery is in that body. Without that machinery, there’s no way to repair the damage. If it’s the axon though, the nerve cell’s body can repair it, although it may take years.

The difference between a coma and a persistent vegetative state is that in a coma, generally the cells are all there (well most of them anyway), it’s just that the axons are all screwed up. Generally as a result of blunt force trauma. In a PVS on the other hand, the cells themselves are dead. Hence the term braindead (the old non-PC term for PVS).

In a coma there is generally brain activity because the cells themselves are still alive. It’s just scattered and disorganized since the wires are tangled and snapped off. Axon growth is inhibited by several chemicals in the brain (that you don’t see in the peripheral nervous system) which is why regrowth can take months, years, even decades…but at least it can potentially actually happen. In a PVS there is nothing. There are no cells to fire. There are no cells to regenerate themselves. There is no chance of recovery.

Terry Schiavo’s brain was gone. This guy’s wasn’t. I don’t want to get overly philosophical here, but if the brain is the seat of the soul and the brain itself is no longer functioning, I really can’t consider it taking her life. Terry was a vacant body, this guy was not.