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 Fridays: Warm Milk

Okeedokee, today is a big one and it may look a little daunting, but it will be totally worth it in the end. I pinky swear.*

Also, I finished this up last night around midnight, so if there are more mistakes than usual, sorry. I'm just too lazy to go through it all right now and proofread (but not too lazy to type this explanation apparently). Anyway, on to the good stuff.

My son was having some troubles going down for naps a while back, so drawing on my own childhood, I turned to a little medicine my folks used to give me to help me sleep: milk (some of you were probably thinking: vodka! Shame on you. Straight vodka is not good for kids. White Russians on the other hand...).** And low and behold it worked. So now before naps and every night before bed, we give our 16 month old a glass of warm milk to help him fall asleep. Could there be some physiology behind it?

People have been using warm milk as a sleep aid for millions of years. If I had to guess, I'd say it correlates with the invention of the microwave. So, probably for the last 2 million years. Before that, they used to just give each other a little smack on the head with a club to help each other sleep (Note: I do not in any way condone domestic violence). But why warm milk? Is warm milk just like a little kid needs his teddy bear to sleep? Is it more psychological than anything else?

There are two theories currently in play right now. The first has to do with proteins, neurotransmitters, the pineal gland, and biochemistry. Big words. But it's not too complicated. So let's break it down.

Remember the pineal gland from back in high school? Probably not. I can barely remember what it does and I'm gonna be a doctor one day. The pineal gland is in charge of keeping time in the body. It does this through a hormone called melatonin (not to be confused with melanin which is in charge of skin color). Melatonin levels are high at night and low during the day. High levels tell your body it's time to sleep and low levels tell your body it's okay to be awake. So if we could artificially increase melatonin levels, we could trick the body into thinking it is sleepy time.

Now for some biochemistry. Melatonin is made from serotonin, which is really a cool hormone and will probably be a topic in the future, but for now, nobody cares about it. Except, that serotonin is made from a protein called tryptophan. So to summarize, tryptophan leads to serotonin which leads to melatonin which is how your body tells time.

When you warm up milk, it releases more tryptophan. So the theory goes that taking in excess tryptophan leads to increased melatonin. High melatonin then makes the person sleepy. While this works on the surface, and may play a small role, it does have some physiology issues. Tryptophan needs high amounts of insulin to cross into the brain. Insulin comes about when the body sees lots of sugar. Drinking milk shouldn't normally cause the high levels of insulin needed for a huge influx of tryptophan into the brain. So for milk to work, a bunch of carbs should be taken with the glass to help stimulate insulin and thus help melatonin cross into the brain. People don't usually load up on sugar right before going to bed though. So this probably isn't the major contributing factor to the sleepiness.

The second theory gets away from the big words for the most part and is the one I currently subscribe to.

Here's what is probably happening. Whole milk has a lot of fat in it. We give our son whole milk, the Romans gave their kids whole goat milk, ancient cave men used to give their kids milk straight from the stegosaurus. Whole milk is probably best for this to work. It sits in the stomach for a little while because of the fat and convinces the body that a good full meal was just eaten and so your body goes into "rest and digest" mode. When the body goes into the "rest and digest" mode, it shunts blood to the GI system and away from the periphery, which includes the brain. When the brain doesn't have blood, it doesn't have oxygen. Lack of oxygen tells the brain to go into sleep mode. And voila! Sleepy time.***

This is a temporary situation though. The body won't be fooled by the milk for long and will eventually return things to normal. So if you are going to drink milk, do it right before bed.

For those of you looking for a nice neat summary, we probably have a combination of the two at play - tryptophan increases the melatonin a little bit and contributes to sleepiness, but the large glass of milk telling hour body to send blood away from the brain is probably the main factor. Either way, milk is good for sleep and now you have some science to back it up.

*Legal note: pinky swears over the internet are non-binding and should not be considered as a real contract unless actual pinky-to-pinky contact was made in the physical world

**Please do not give your children alcohol ever, even if it sounded like a good idea when you read it on a blog.

***side bar - this explains why you feel sleepy right after lunch when you head back into work. Most people grab a McDonalds or some other fast food high in fat. Your body thinks it needs to supply your digestive system with blood and it borrows from the brain's supply. If you were to eat a small meal at lunch and another snack a couple of hours later, you would probably find you are less sleepy and have more energy to make it through the afternoon.

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.

Physiology Friday: HCG

So the goal of Physiology Fridays is to explain things we see in our every days lives a little less hocus pocus and a little more sciencey. Today we are gonna talk about HCG injections and their role in weight loss.

For the longest time, I thought injecting yourself with HCG was complete and utter nonsense. While I still feel that way, at least now I can see that there is science behind it. So get prepared, the physiology is gonna come fast and furious today.

First we are going to get crazy and split up HCG into two parts. We will call them alpha-HCG and beta-HCG. Hopefully you are still with me so far.

A lot of people have heard of beta-HCG - the "pregnancy hormone". This is the hormone that we are looking for on a pregnancy test when a woman pees on that little sticks you buy at Walgreens. Fun fact: they all look for the same hormone, so buying the $40 stick doesn't work any better than the one bought at the dollar store. But I digress.

Alpha-HCG is kinda like a jack-of-all-trades. He looks a lot like a number of other hormones the all human bodies produce and can do their jobs too (for those of you keeping track - FSH, LH, and TSH). This is why we don't measure alpha-HCG for pregnancy tests. Dudes would be testing positive for being pregnant. And that's not right. So since alpha-HCG can do the jobs of these other hormones, scientists decided to take advantage of that and put alpha-HCG to work.

One of the hormones alpha-HCG can mimic is TSH (thyroid stimulating hormone). TSH tells your thyroid to secrete more thyroglobulin. Right now, you're probably asking yourself, "Who cares?!!" But let me tell you, thyroglobulin is important. One of the things it does is produce T3 and T4 which raise your BMR (basal metabolic rate). This means that it tells your cells to burn energy faster. A faster energy burn, means you go through more energy in a given time. If you can control the amount of calories you take in, your body will have to search for other places to get energy - and voila! You break down fat.

So that's the theory. Does it work? It seems the answer is a resounding "We don't really know." None of the studies I found were very good. Some didn't take into account long-term effects, and some were just downright wrong. Which leaves us with the question, "Should I use HCG as part of my weight loss program?" If you have a few extra bucks and are willing to live life on the wild side where you inject your body with foreign substances, then that's up to you. Just don't come complaining to me when your pregnancy comes back with a false positive...

*A couple of web sites claim that HCG is responsible for decreasing mom's use of sugar during pregnancy so that there is plenty for the growing baby. They claim that it works the same way in this weight loss program. While this is partially true, HCG may have a small effect on lowering sugar use, this is a very small benefit at best. The hormone they are really talking about (whether they know it or not) is HPL(human placental lactogen). HPL directly antagonizes the effects of insulin so the cells in your body (except for BRICKLE) cannot take in sugar. This leaves more sugar for the growing baby to use. HCG's primary weight loss effect is due to its ability to raise the BMR as a result of its mimicry of TSH.

Physiology Friday

It has been a busy morning already. Looks like we are gonna have a lot of Good Friday babies. How exciting.

With that in mind, today's cool physio is brought to you by my wife, who recently said, "I don't really know that much about menopause." Hopefully she still has a couple of years before it hits, but it's never too early to learn.

Before you completely zone out with a sigh and a "menopause is so boring," don't worry, we are gonna start off slow. This morning we are going to only hit the very cool subject of hot flashes. Oh yeah. We're gonna go there.

Some background first: menopause is when a woman's ovaries begin to fail. They no longer send out eggs and, more importantly, they don't send out their usual supply of hormones to the rest of the body. The main hormone that the ovaries are crucial for is estrogen. And today it's all about the estrogen.

You see estrogen, among the many things it does, is a muscle relaxant. It's one of the reasons women have a typically lower blood pressure than men - their blood vessels are more relaxed. It's one of the reasons women are typically more flexible. Estrogen makes those muscles a little more relaxed. Take away point: estrogen=muscle relaxant.

*(I'll explore estrogen a little more at the end, but it will be a bit more technical, so feel free to skip that part and just move on to the next paragraph)

So when a woman experience a hot flash, it is her ovaries playing the hero. They are giving a last ditch, dying effort to squeeze out whatever estrogen they can. That burst of estrogen then hits the blood vessels and causes them to dilate. When the blood vessels near the skin dilate, warm blood, right around 98 degrees, rushes to fill the empty space. Her skin turns red and she feels warm and sweaty.

And there you have it, hot flashes explained. Making the estrogen connection.

*For those of you still reading, let's take this a little further. This explains why an S3 is considered normal in an adolescent female. She has high levels of estrogen causing her heart to be more relaxed. As her estrogen levels begin to approach a more stable level, the S3 should disappear. The estrogen connection also helps explain why a pregnant woman, who has elevated levels of HCG leading to elevated estrogen, is at a greater risk for DVTs - the high estrogen relaxes veins and allows for pooling of blood and subsequently clot formation (Estrogen also causes increased production of liver proteins leading to increased clotting factors, except for XI, and so between the two factors, we see a higher incidence of DVTs in pregnant women).