Neuroanatomy | Neurotic Physiology

Archive for the 'Neuroanatomy' category

When you throb with pain...are you feeling the beat?

Jul 11 2012 Published by scicurious under Behavioral Neuro, Neuroanatomy, Physiology/Pharmacology

I think we've all had that kind of pain. A headache, maybe, or an injury. The kind of pain...that THROBS. You know what I mean. When I get one of those throbbing headaches, it's like every beat of my heart is pushing the blood up through my brain, and with the blood comes another throb of pain. I feel like my head throbs in time with my heartbeat, and will even try to relax and slow my heart beat down to at least slow the throbbing a little. It never works.

And it turns out there's a reason that it doesn't work. Because it turns out that pulsatile pain has nothing to do with heartrate. And for this study, all the authors needed was a heart rate monitor...and some very long-suffering dental patients.

Mirza et al. "Is There a Relationship between Throbbing Pain and Arterial Pulsations?" J Neuroscience, 2012.

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8 responses so far

SCIENCE 101: Cranial Nerve IX, The Glossopharyngeal Nerve

Jul 11 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Physiology/Pharmacology

After somewhat of a hiatus, the cranial nerves RETURN! After all, we can't quit now! Only four more to go. And here's where we're at:

Oh: Olfactory
Oh: Optic and Optic 2
Oh: Oculomotor
To: Trochlear
Touch: Trigeminal
And: Abducens
Feel: Facial
Virginia's: Vestibulocochlear and Vestibulocochlear 2
Gucci: Glossopharyngeal
Vest: Vagus
Ah:Accessory
Heaven: Hypoglossal

So we're up to cranial nerve IX, the Glossopharyngeal.

And for function:

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

Where 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. So you can see that the glossopharyndeal is going to have both sensory and motor fibers, which is going to make it that much more complicated.

But that's ok. Repeat after me: Glossopharyngeal. Glossopharyngeal. Doesn't it just SOUND nice? Like an onomatopoeia of what happens when a sip of delicious Coca-Cola Slurpee slips over the tongue and fizzes a little at the back.

And speaking of Slurpees...well what did you THINK the glossopharyngeal did?

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SCIENCE 101: The Vestibulo part of Cranial Nerve VIII, the Vestibulocochlear Nerve

Jun 20 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Uncategorized

Sci loves Portal. I think it's a magnificently clever game, and Portal 2 is the in the same vein. I love the songs, I love the humor, and I love the concept (puzzle solving with a giant gun! That makes portals!), and I DESPERATELY want to play.

I can't.

Sci, not unlike many people on this planet, is a sufferer of motion sickness. I've never been able to read in the car, and sitting in the back seat is often too much. Heck, sitting in the FRONT seat is sometimes bad! And Portal. Whooooo, Portal. Just WATCHING Portal makes me green in about 2 minutes, and attempting to play myself...well I only lasted about 30 seconds.

Motion sickness is caused by a mismatch between the perception of movement (say, moving in a car), and what your sense of balance perceives (that you're sitting still). Finally the difference in perception causes dizziness and nausea. It's stronger in some than in others, and for those of us who are really weak of stomach, well, we can thank an overactive vestibular system.

Last week we covered the basics of the auditory system, controlled by cranial nerve VIII, the vestibulocochlear nerve. But the "vestibulo" part of the vestibulocochlear nerve is, though in the same general location, something else entirely. Because cranial nerve VIII not only controls your hearing (the -cochlear part), it also controls your BALANCE and sense of how you're moving through space. While this may seem to most people like it's merely a matter of avoiding sharp objects and not embarrassing yourself on the dance floor, knowing your orientation in space is a universal issue for all living creatures. It's something we don't really think about, but are you facing up or down? Where is your head relative to your feet? When you're moving forward, how do you know how FAST you're going? These are all questions for your vestibular system.

And the vestibular system is OLD. All jawed vertebrates, you and the fish you just ate, and the chicken you had for dinner, pretty much have the same vestibular system setup.

(Click to embiggen)

You can the the cochlea sitting there, like a cute little snail, right where we covered it last time. Now, look just above it and slightly to the left. You see those two arches? Those are part of your semicircular canals. And those loops detect position and acceleration...and determine whether you're feeling motion sick.

If you'll excuse me, I'm feelin' a bit queasy talking about all that acceleration...

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SCIENCE 101: Cranial Nerve VIII, part one, can you hear me now?

Jun 15 2011 Published by scicurious under Behavioral Neuro, Neuroanatomy, Uncategorized

Today we move on in our tour of the cranial nerves to another nerve that is basically responsible for an entire system. In fact, it's an overachiever...and does TWO. We've had the olfactory and the optic, and now, we welcome the vestibulocochlear, which does both auditory AND your sense of balance.

The auditory system is one of my favorites (I've always had a soft spot for the trochlear nerve, I don't know why, but this is the other favorite), because the interior of the ear is just so PRETTY. It's full of caverns and arches, delicate hairs and membranes. It really is very pretty.

(See?)

I have to warn you, this is a really large and complicated system, right up there with the eye. So we're going to start with just the auditory portion of the vestibulocochlear nerve, and we'll cover the vestibular portion next time.

5 responses so far

SCIENCE 101: Cranial Nerve VII, The Facial Nerve

Jun 06 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Neuroscience, Uncategorized

Ok, I had a lot of fun writing about the Trigeminal. Making it all about a Bollywood movie makes EVERYTHING better. Unfortunately, Bollywood movies do not apply to everything (but they DO apply to most things).

So now, we move on to Cranial Nerve VII, the Facial nerve. Why, you say, WHERE was Cranial Nerve VI? I covered it with cranial nerve IV, actually, the trochlear and abducens together, since both innervate very similar muscles in the eye.

And so now we move onward to cranial nerve VII, the facial nerve. This is another mixed nerve, one that does BOTH sensory and motor functions. And being the facial nerve, it's ALL about the FACE.

The question becomes: can I illustrate this ENTIRE post using nothing but pictures of different facial expressions?

(This is an example of an internet meme known as rage comics. They are user made and thus only sometimes funny, but i discovered them via this, which is both funny and horribly, horribly true. Basically, you have a limited number of faces, male or female, and you make comics out of them, and they all look a little like this guy. And I hope whoever invented them (I think it's Reddit) doesn't hurt me, cause I love Reddit. If you think these are funny, you can build them yourself, using the memebuilder, which is what I used for all of these).

12 responses so far

SCIENCE 101: Cranial Nerve V, the Trigeminal

Jun 01 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Uncategorized

You know, doing a series on the Cranial Nerves can get you down sometimes. I know this thing is going to be MAD useful for everyone (and may already be useful to many of you!) when it's done. But right now, it's "blah de blah nerve goes to the herp derp nucleus located in the blort de blort and innervates the doodads...". It's all a little formulaic and can get kind of...old. And Sci don't DO old.

So I was reading all about the Trigeminal, and trying to think of a way to spice it up a little. And then it occurred to me. The trigeminal nerve and what it innervates can be ENTIRELY explained with the major plot points of a Bollywood movie.

If you don't know what Bollywood is, well you're missing out.

(Completely random time periods? Check. Highly suggestive moves without ANY KISSING EVAR? Check. Entirely random plot points? Check. Folks, we have BOLLYWOOD!)

Bollywood refers to a very specific kind of movie in the Hindi language, produced in India, and specific (often) to Mumbai. It's got some very specific themes: Wildly incongruous, high energy song and dance numbers (Bollywood movies are ALWAYS musicals), highly melodramatic plot points (an evil villain tying a girl up on the train tracks is par for the course here), and the "almost kiss" which is about the sexiest thing you can get away with when making movies in India. And Bollywood...is wildly entertaining. Seriously. If you ever want to sit back with some popcorn and some seriously entertaining movies, I totally recommend Bollywood.

But melodrama. Let's talk about melodrama. Because if there's any nerve that does drama, it's the trigeminal. Here we go.

9 responses so far

SCIENCE 101: Cranial Nerves IV and VI, the Trochlear Nerve and Abducens Nerve

May 30 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Neuroscience, Uncategorized

Today we continue ONWARD with the series on the Cranial Nerves. But we're doing something a little different. Because last time we covered the Oculomotor Nerve, which innervates FOUR of the SIX muscles which control the eye, today we're going to round out the eye (heh, round, eye, heh) and do the other TWO. But we're going to have to go out of order. The order of the Cranial Nerves (with convenient mnemonic!) goes like this:

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

We've been through the Oh, Oh, Oh (cranial nerves I, II, and III), but the two cranial nerves that control motor movements of the rest of the eye are NOT IV and V. Instead, they are IV and VI, the Trochlear Nerve and the Abducens. And we're going to cover them together, because each one is a motor nerve that moves exactly one muscle, and each one sends signals out from exactly one nucleus. Nice and relatively simple.

So here we go. And we'll start out seeing where they peek out from the brain:

You can see the trochlear nerve poking out, all thin, just to either side of the top of that rounded trapezoid that is the basal pons, while the abducens comes out of the bottom of the basal pons.

3 responses so far

SCIENCE 101: Cranial Nerve III, the Oculomotor Nerve

May 23 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Neuroscience

In the last few posts we've covered the first two cranial nerves, the Olfactory and the Optic nerves (remember our mnemonic: Oh, Oh, Oh, To Touch And Feel Virginia's Gucci Vest, Ah Heaven). Both of these cranial nerves carry sensory information IN to the brain for processing, and don't really control motion. For nerves like the olfactory, you wouldn't expect much motion (can't really move our nose around very well), but for the visual system, eye movements are extremely important, allowing you to focus the eye on the things that are most important in the visual field. Being able to do this accurately and at speed is extremely for complete processing of our visual field.

So today is for the third "Oh", the oculomotor nerve. Move those eyeballs!

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5 responses so far

SCIENCE 101: Cranial Nerve II: The Optic Nerve, Part 2.

May 18 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Neuroscience

Last time we talked about the very basic anatomy of the eye. It was a lot of material. It's too much. For you, I will sum up.

Light and images come through the cornea and hit the lens. The lens flips the image backward. The light continues to the back of the eye, often to your area of best focus called the fovea, where it filters through the layers of cells to hit your rods and cones. The rods and cones send signals to bipolar cells, which send signals to ganglion cells. The axons of the ganglion cells mass up at the back of eye and head off as your OPTIC NERVE!

Got it? Good. If you want more, please head over to Monday's post!

So, an image comes in. It will get flipped BACKWARD. It will hit the first cells LAST (the rods and cones are actually buried beneath several other layers). From here, we will go along to the back of the brain, and on the way the information will get flipped upside down. And then our brain processes it, and everything's all right.

So, the image has come through. We're past the lens, and everything is backward.

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SCIENCE 101: Cranial Nerve II: The Optic Nerve, part 1, aka, the EYE

May 16 2011 Published by scicurious under Basic Science Posts, Neuroanatomy, Neuroscience, Uncategorized

...or rather, the visual system. Cause you can't really talk about the optic nerve unless you talk about the rest of the eye along with it.

We humans rely pretty heavily on vision as a species. At least, being able to see is a lot more important to our daily lives than, say, being able to smell. But the visual system is, in many ways, surprisingly simple. In many OTHER ways, it's confusing as all get out. I will do my best.

So, I'm going to start with this: an image is going to come in. It will get flipped BACKWARD. It will hit the first cells LAST. It will then go along to the back of the brain, and on the way it will get flipped upside down. And then our brain processes it, and everything's all right. It's opposite day, my friends!!!

Got it? Good.