Physiology Fridays: Why you seem to pee more when you go to the movies

It's movie season right now, so today's post is both topical and fairly practical. On a very related note, go see "The Avengers", it is amazing. Seriously, stop reading right now, and go see it if you haven't already. It really is that good.

Also, buckle up your seat belts, this is gonna be a long one. But it's totally worth it. Probably.

Anyway, back on topic. When I go to the movies, I get my coke and my salty popcorn, settle into my cushy seat, and prepare to be entertained. Then about 5 minutes into the movie, I feel like I haven't peed in weeks. So I sneak off to the restroom, take care of business and come back. I get all situated and prepare to enjoy the rest of the movie. A half hour later, it hits again. I have to pee so badly I'm considering urinating in my now empty soda cup because I'm not sure I can make it to the bathroom in time. Once again, I creep past everyone else, empty my bladder, and then stumble around blindly trying to find my seat, where I remain for the rest of the movie. When the credits finally role around, I jump out of my chair and bolt for the restroom one last time. And this happens every movie! But why? Let's take a look at the physiology.

There are two major players here in this crazy game of "Don't Wet Your Pants", the first is water. Most of that 32 oz soda I'm guzzling down is water. When water comes in the body, it also must leave. This part is straight forward.

The other player in this dangerous game of "try to leave the movie seat as dry as when I sat down", is sodium. Sodium makes up half of what we call salt. Salt's chemical compound is NaCl, which means that it is made up of equal parts sodium (Na) and chlorine (Cl). And if you are like me, you dump salt all over your popcorn. But sodium isn't just found in salt, there is also a very significant amount in coke (and in most soft drinks).

So we have two ways of sodium getting into our bodies right now, salty popcorn and our soft drink. Why is this important? Sodium loves water. Or maybe water loves sodium. I don't know which it is. All I know is that if you see sodium go to the park, water follows right along and goes to the park too. Or maybe it's that sodium goes to the park and loves water so much that he brings water along with him. And they go to the bank together, and the gym, and to the movies, and grocery shopping, and they go down slides together, and they have nerf gun fights. They really, really like each other, whatever the relationship is.

Anyway, sodium is readily absorbed into the body by the small intestine (specifically in the jejunum). So as sodium is leaving the small intestine, it says to its buddy water, "Come with me, it'll be fun!". So water, being the great molecule it is, follows its pal sodium into the body. (There are plenty of other molecules that bring water into the body with them, like glucose, but today our big focus is on sodium)

Now we just talked about how much sodium we take in at the movies - a lot! All of that sodium pulls in all the water from your intestine into your blood along with it. Now you have an influx of fluid into your blood stream. And this is no turn on the faucet, and fill up a water balloon flow, this is open up the fire hydrant and fill up that same water balloon flow. The good news is that your body knows how to deal with this sort of conundrum. Your body knows that exploding from too much water coming in is a bad thing. And while there are a couple of different response systems, since I just got done with cardiology, we will talk about how the heart response affects things.

The heart has stretch receptors inside of it in a portion called the atrium. These stretch receptors do exactly what they sound like, they alert the body when they are stretched. And the only normal way they get stretched is when excess fluid comes in the heart and pushes up against them. When these receptors get activated, they send out a signal called ANP (Atrial Natriuretic Peptide - atrial = atrium, natriuretic = sodium, peptide = signaling protein). ANP travels by blood to the kidneys where it tells the kidneys to get rid of sodium. The kidneys send sodium into the urine. And like we talked about earlier, wherever sodium goes, water likes to follow. So we send out a ton of water into our urine. The bladder fills up rapidly and then you feel like you have to pee. This will continue to happen as long as the heart feels stretched enough to send out ANP. Or basically until you stop cramming your face with salty popcorn and sodium-filled soft drinks.

So how can we prevent this, or at least lessen the effects of this? The obvious way is to not eat salty popcorn or drink soda. Bam! Problem solved.

But if you are like me, and you love your movie treats, then there are other ways. The first is to limit the salt on your popcorn and drink a soda with less sodium in it (a good rule of thumb is clear sodas have less sodium, colas have more, and diet sodas have more). Or you could try eating a fatty meal right before you went into the theatre. This would slow down the whole digestion process and possibly delay the water absorption for long enough that you could finish your movie in peace. Of course you would suffer for it later, but we aren't dealing with that here. We just want short-term results. Another option is to have a folley catheter inserted, then you could just have your bladder drained while you watch. You could drink 3 or even 4 sodas and have like 20 bags of popcorn and not have to run to the bathroom once.There is the possible complication of a urinary tract infection or other worse things (much, much worse) but it's an option to keep on the table.

The last option is Depends. A pair of adult diapers is both practical and beneficial. I don't know about you, but I usually end up freezing in the movies and it wouldn't be a bad thing to have some extra warmth mid-way through.

However you solve the problem, at least now you know the physiology behind it.

(Also, sorry for the boring stock photo at the beginning. I just couldn't find anything funny that fit and wasn't too inappropriate. So here is a funny pic that is somewhat inappropriate and has nothing to do with the post)

Physiology Friday: How to tell if your are getting a viral infection

It's Physiology Friday again. I had to take a test this morning and it threw the whole day off for blogging. Sorry.

Anyway, on to the physiology. I was talking to a friend the other day and mentioned that I knew I was getting sick because all of a sudden my skin got really dry and flaky. This friend looked at me like I was crazy. Not that I'm not crazy. No. That's a very accurate diagnosis. But that particular statement was actually based on, you guessed it, physiology.

Let's back up a little. First, you need to know something about your body. Your body is made up of cells. Bam! You just survived BIO 101. Some of these cells grow and reproduce quickly and some grow and reproduce slowly. Bam! Bam! BIO 102. This is the easiest class ever. Now if you are keeping up, this next point shouldn't be too much a stretch. The cells that grow and reproduce quickly need more energy. They are like teenage boys, always eating whatever they can get their grubby little hands on. Some of these cells can be found in your hair, in your GI system, in your respiratory system, and in your skin. They all need lots of energy to function properly.

When you get sick with a virus, the virus stages a hostile takeover. It comes inside the cell and says, "Stop what you're doing! You must make 5 gazillion copies of this beautiful me that you see before you." And since the cell is used to blindly following orders, it stops everything and goes into full on production of viruses. This takes a lot of energy. A lot. Of. Energy. Do you see where the problem comes in?

When only one cell is doing this, it's no big deal, your body has extra energy to spare normally. When there are a bunch of cells doing this, your body begins to run out of energy. And so the cells that need a lot of energy to function normally begin to suffer. This explains why your hair feels more brittle when you are sick. This explains why you might even notice your hair falling out more when you are sick. This also explain why your skin is dry and flaky when you are sick. Your body is sending crucial nutrients to cells making viruses and not enough to cells responsible for replenishing your skin. And there you have it, dry skin will often precede a viral infection.

It's physiology baby. I might have a little crazy, but I got me some science too.

*if you are really good at connecting the dots, you will see that this is why pregnant women often have clumps of hair fall out while pregnant and why they complain of dry skin - they have a baby sucking up all their energy.

Becoming Rainman

So the other day, I was seeing a patient with my doctor. We were calculating the due date for our pregnant patient's baby and it came out to be October 31st. My doc absentmindedly said, "I wonder what day of the week that is?" To which I promptly responded, "It's a Wednesday." She gave me a quizzical look. I wasn't looking at my phone or a calendar. I could see it in her eyes, she made the call - I was no longer an idiot. I had been upgraded to idiot savant.

Now what I actually did was cheat. You see there's a system of knowing days of the week by knowing the date - you just need to know a single anchor day. Every year but leap year, that day is January 3rd. Since this year is a leap year, the day is the January 4th instead, which is a Wednesday this year. Now we need some other easy to remember reference points - 4/4, 6/6, 8/8, 10/10, 12/12, 7/11 and 11/7, 9/5 and 5/9. These dates all share the same day of the week as our anchor day. When my doc asked about October 31st, I just took 10/10, which I knew to be a Wednesday, and then moved forward 3 weeks, and voila! What if she had asked about August 10th? I take my reference point of 8/8 and move forward two days, and I know August 10th is a Friday.

Look, this doesn't come in handy all that often, but it sure is a fun way to convince people you are really smart. Or you can use it to convince people that Tom Cruise is your long lost brother and you should go to the casinos and play some blackjack.