November | 2013 | Forgotten Physiology

Is that the same devil you had in mind? Twins!!

There’s public radio telethon week, toll roads, vending machines that give you Diet Pepsi when you clearly pushed the “Coke” button, and near the top of the list are hiccups. These are a few of my least favorite things. Oh, you know this guy loves the human body. There are few marvels in this world more elegant, more profoundly complex than the body and it’s nuts and bolts, but son of a [CENSORED], hiccups are the devil! I seriously doubt that a successful pick up line has ever been delivered while battling with the hiccups. Hiccups lie in wait like mean-spirited hecklers waiting to kill the mood of your acceptance speech or interrupt the punch line of your best dirty joke. So in this episode of Forgotten physiology we’ll pose the question; Hiccups, what’s your deal?

Yes, I prefer to think of my hiccups as the old men from the muppet show
http://www.youtube.com/watch?v=PGfx3QAV64M

Synchronous Diaphragmatic Flutter (or Miss Jackson if you’re nasty)

Mechanically speaking, hiccups are nothing more than spasms of the diaphragm; short, involuntary contractions forcing air through the windpipe that is then immediately closed off by the tough, elastic flap of the epiglottis. This closes off the vocal chords like a trap door that says “No more air for you! No!” and produces that signature, sexy frog sound of a classic hiccup.

The phrenic nerves begin in the cervical vertebrate (C3-C5) and zip line down between the heart and lungs to connect with the diaphragm.

You have a left and right phrenic nerve that connect to the diaphragm to control its contractions and receive sensory input in return. “Sensory input?” Well sure, you don’t just blindly send out messages. You look for a response. Your nervous system is all touchy feely and needs to be able to sense where everything is…no organ left behind. Those nerves are the only electrical wiring operating the movement of the diaphragm. So any significant disruption or irritation of the phrenic nerves can cause spasms and ultimately hiccups. For example, if you just had a bad breakup and decided to go Tazmanian Devil on 2 large orders of pork fried rice from Wong’s Wok, a full or distended stomach can press on the phrenic nerves and trigger hiccups.

But who is really in control?

We may not think about it but the diaphragm is made of “skeletal” muscle. If you remember our chat from muscle mania, skeletal muscle is under the control of the somatic nervous system. This typically means that it is under our control. We can, for example, contract our diaphragm muscles ourselves and draw in a deep breath. However, we don’t exactly tell our diaphragms to spasm do we? Ahh…here’s where it gets interesting.

A thought experiment..

You and your body are one and the same right? I mean you don’t feel separate from your body do you? If I ask you to pass the mashed potatoes you don’t ask your hand to grab the bowl. Your brain and your hand flow together, without interruption.
Now think about a hiccup. Does that ever feel like something YOU did? No way, the hiccups happen as reflex and your brain gets the feedback. These are controlled by a “reflex arc,” neural pathways (composed networks of neuron cells) that connect to the spinal chord BEFORE reaching the brain. Some neural pathways have a long way to go to reach the brain, your central command center. The spinal chord works like an intermediary traffic control center, managing the local stuff and all the sensory input from the extremities. This allows motor reflexes to occur instantaneously without checking in at the office (brain) first. Your brain isn’t left out of the loop. The motor neurons of the spinal chord are simply the first to respond.

But why me? Why?!!!

Typically when we get the hiccups we were eating too much or eating too fast, drinking too fast, or hitting the sauce a little heavy (either alcohol or carbonated beverages). Episodes can also be brought on by excitement. I’ve always said that too much happiness is dangerous. These hiccups don’t last long and typically resolve on their own without tongue pulling or drinking water upside down.

There are of course persistent hiccups that are linked to an encyclopedia worth of clinical problems ranging from stress to heart issues to neurologic and metabolic disorders. So if 48 hours have gone by and you’ve still got the chirps then it’s probably a good time to see your doctor my friend.

Stay curious, stay classy, and never stop learning my friends 🙂

you know that hat is very slimming

Here’s the truth of it. Mother Earth, the blue planet, our very own 3rd rock from the sun is perfect for us. By that I mean this planet has more than enough places (from Bangkok to New Jersey) that are both warm and cool enough for us to survive and thrive as a species. Our solar system is a rough neighborhood. Even on the surface of the moon there is at least a 450° F difference between standing in the light and the shade. So believe me brothers and sisters when I say that it is truly remarkable that we get to hitch a ride on this cosmic trolley called Earth.

Asashoryu is not impressed by your skinny jeans.

The human body has special needs. Our metabolism functions optimally within a narrow, warm fuzzy range between 36.5° C and 37.5° C (98-100° F). Most of us don’t climb much further than 98.6° F (hyperthermia) unless we’ve caught a nasty flu virus or overslept on a tanning bed. Now that is one tight range for homeostasis to be maintained. I’m talking tighter than a sumo wrestler in skinny jeans. This is the range where our enzymes can function optimally, where our cells can use energy stored in glucose, where blood can adequately deliver oxygen in exchange for carbon dioxide, and an [EXPLETIVE] load of other vital, biochemical gymnastics.

“Hypothermia” – is not an 80’s Hair Band

Medically speaking, hypothermia is the state at which your core body temperature drops below 35° C (95.0° F) but I’m willing to bet that for your core temperature to slide down even 3 degrees you’re already feeling pretty cold and have been for some time. If you put the lid on a warm cup of coffee and set it in the freezer you’d be lucky to find iced coffee waiting for you even a half hour later. The human body has water tight skin, fat tissue, body cavities, and many times the volume of a 16 oz cup of Joe. So when we get cold it’s the real thing and our body fights for us right up to the very end.

A word or two about Vasoconstriction

Consider that the blood flowing through our veins carries heat. So when we start to lose heat the blood becomes a kind of heat currency that the body gets mighty stingy with. So when the air gets frosty the blood will begin to move away from the small, surface vessels in the skin and concentrate its energy on the brain and other vital organs. The skin is also what is exposed to the cold air and where 90% of body’s heat is lost.

The Shiver

When it comes to survival by any means necessary my team captain will always be the hypothalamus. We actually have a shivering center of the brain located in the posterior hypothalamus, which is normally kept in check by the anterior portion of the hypothalamus. However, when the body’s core temperature drops just below it’s warm fuzzy range your posterior hypothalamus kicks in and says “everybody dance!” This leads to the short, rhythmic muscle contractions in an effort to generate heat.

So what happens when the big chill hits?

Stage 1 (mild – “Time to put the snow balls down and come inside”)

This occurs after a 1-2° drop in normal body temperature. Shivering, hypertension, tachycardia (heart rate over 100 rate/minute), and vasoconstriction (contriction of blood flow through vessels). Clinical cases vary in which hyperglycemia or hypoglycemia (high and low blood sugar) have occurred. The chances are roughly 50/50. As metabolism staggers the cells decrease their uptake of glucose and the tissue’s sensitivity to insulin becomes impaired allowing glucose to spill into the blood. This is a hyperglycemic state. However, having a low blood sugar to begin with (especially if you’ve been wandering around for hours in the cold) can accelerate the onset the onset of hypothermia.

Stage 2 (moderate – “Dude, you don’t look so good”)

Loved that movie 🙂

This is seen after a 2-4° drop from normal. Ok we say moderate but by this point you’re pretty gosh dang cold and have been for some time. The surface vessels of the skin constrict, drawing blood to the vital organs, shivering, coordination, and mental state all worsen. Portions of the body rich in capillaries like fingers, toes, lips, ears (basically all the delicate parts most exposed to the air) all get pale and blue, and not in that sexy, Avatar kind of way.

Stage 3 (severe – “Somebody call an ambulance!”)

At this point the core temperature has dropped below 32° C and your body is pissed. The heart rate drops down to the 30s (normal resting heart rate for adults is at least 60 beats per minute), the respiratory rate decreases, the blood pressure drops. It’s like the temperature just turns your volume down. The vital organs are beginning to fail as metabolic functions stagger. Your muscle coordination and mental function are terrible by this point and you’d be lucky if you can unscrew the loose lid on a peanut butter jar or remember the words to “Happy Birthday.” Then something really, really strange tends to happen…

The Deadly Strip Tease

It’s a phenomenon referred to as paradoxical undressing. People at the edge of their sanity, in the most severe stages of hypothermia will begin taking off their clothes. They reach a state where they become hellah-confused, disoriented, and even violently aggressive where they just start shedding layers as if they were burning up. One theory is that by this point the body has been so beaten up that the signaling pathways of your hypothalamus are sending all the wrong messages like an evil cell phone that sends “let’s get back together” texts to all your ex’s. This is also associated with a “hide and die” syndrome (terminal burrowing). Victims are sometimes found curled up in small, hidden spaces. I don’t know physiology fans, perhaps in moments of extreme circumstance human beings simply switch back to our most primal selves.

So because I care here’s an ounce of prevention…

If you’re out in freezing temperatures stay dry (wet skin is a death sentence), wear multiple layers especially synthetic, poly blends that retain heat better then cotton, stay hydrated but avoid cold liquids that will just further lower your core temp, cover your head, and NO no no alcohol! It’s a vasodilator (increases blood flow in the vessels) drawing blood/heat to the extremities and thus away from your core. That rum n coke just isn’t worth it.

As always stay curious, stay classy, and never stop learning my friends 🙂