SCIENCE 101: Introduction to the Cranial Nerves

I've been waiting for a while to take on another multi-part project (ok, I needed to recover from EB first), and now I think it is TIME. Time for a series SO LARGE that it's going to take me probably more than three weeks, or even four to finish (with breaks for Friday Weird Science, hey, I know what you're really here for). This is going to be INTENSE.

Today I would like to introduce you to the CRANIAL NERVES. When many people think of nerves, they tend to think of white, ropey kind of things which go down your hand. You know, like this:

The nerves that we tend to think of are bundles of neurons which extend from the central nervous system to provide impulses to, and receives sensory information from, various areas of our body. Most people think that these nerves extend exclusively from the spinal cord, and that all the impulses that you need travel up and down via the spinal cord. And these nerves certainly exist and you couldn't do a whole lot without them. But what a lot of people don't know is that a large portion of your body is innervated DIRECT from your brain, with nerves that we call the cranial nerves (because they emerge from, you know, the cranium). There are twelve of these cranial nerves, and over the next several weeks, you all will be getting a crash course in neuroanatomy as I go through them in detail, where they come from, where they go, what they are generally responsible for, and what happens when they are not working properly.

You can see the twelve cranial nerves listed in the photo above. Numbered 1-12, grad students in neuroscience and medical students in anatomy have to remember them all, as well as their characteristics (luckily for you, there will be no quiz at the end of this lesson!). To help in these we've contrived various mnemonics over the years. My favorites (the ones that aren't horribly dirty) are below.

Oh, Oh, Oh, to touch and feel Virginia's Gucci vest, ah, heaven.

That silly sounding one (ok, there are versions that are dirtier and not politically correct, so we'll stick with this one for now). The first letter of each word corresponds with the name of a cranial nerve in ascending order:

Oh: Olfactory
Oh: Optic
Oh: Oculomotor
To: Trochlear
Touch: Trigeminal
And: Abducens
Feel: Facial
Virginia's: Vestibulocochlear
Gucci: Glossopharyngeal
Vest: Vagus
Heaven: Hypoglossal

Over the next few weeks I'll go over each of these. I've been an enthusiastic teacher of neuroanatomy for a few years now, and I cannot wait to tell you all which are my favorites (I have ALWAYS had a soft spot for the Trochlear nerve, isn't it SO CUTE, all hangin up in there all tiny!). But to give you a quick idea of function now, I'm going to start with another mnemonic that we use. This one is specifically for the type of innervation for each nerve.

Some Say Marry Money But My Brother Says Big Brains Matter Most.

In this case, the first letter of each word (they are all S, M, or B), corresponds with the functional role, where S is sensory, M is motor, and B is both. I'll be going into what that means and what happens to that information in the next few posts. I only wish I had some easily dissectable sheep brain around here for you all to follow along and get your hands dirty (nothing quite like dissecting a sheep brain to get you the feel for your cranial nerves, and you'll always get a good memory of anatomy jogged with the nasty smell of preservative!).


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