Fall 2014

The Cercal System
Tom Crew, Rana Ozdeslik, Tom Ricci
Have you ever tried to catch a grasshopper with your bare hands?  Hard, right?!  Have you ever wondered why?  Well, you might be slow, but it is mostly because of an extraordinary biological sensory system called the Cercal System.  The cercal antennae (also known as cerci) are located at the rear of the abdomen of the insect (grasshopper?)  This essential defense system can be found in many insects like: grasshopper, groundhopper, katydid, locust, sand treader, weta, lubber, acrida, walking-stick, leafinsect, praying mantis, silverfish, cockroach and cricket. Just to name a few. The cerci are the primary line of defense to an outside threat.  It has evolved over millions of years and has proven to be a valuable asset and an important key to many insect species’ survival.  So how exactly does the Cercal System work?  When you attempt to catch a grasshopper with your hands, the movement of your hands pushes the air in front of it. That air current arrives at grasshopper much sooner than your hands..  When an air current reaches a grasshopper, the cerci sense and inform the insect to react to an incoming threat. It does this by sensing subtle changes in the air currents around it.  Each cerci contain approximately 500 to 750 delicate hairs and 1,000 to 1,500 hair receptor neurons. Each hair is capable of sending a neurological signal to the brain.  When the air current bends the cercal hairs, the hair receptor neurons send a signal to brain through the nervous system. Depending on the pattern of the air current, the brain determines whether or not the grasshopper is in danger.  If so, it sends a signal back to the legs telling the insect to jump and escape.  This system has ensured the survival of many species of insects. So next time you try to catch one, remember that you are up against a defense system that has evolved over millions of years to perfection, and well, you might just be too slow.

Synaptic Pruning
Elisabeth Evans, Denali Schmidt, Alexandra Urban
You look at a coffee cup, you see a coffee cup. But what if when you looked at the cup, your eyes sent signals to the auditory center of the brain? Not only would you see the coffee cup, you would start hearing things too…  How distracting! Now imagine how confusing an entire city would be with all this overlapping sensory information. Well, this might actually happen if we didn’t have synaptic pruning.  What is synaptic pruning?  Inside your brain, there are interconnected groups of neurons called neural networks. The neurons communicate through synapses to make up these functional networks.  Let’s look under a microscope. Scientists are able to isolate brain cells in a dish and observe them over time moving and communicating with one another. The synapse is where this communication happens.  When you are a baby, you have a lot of these synapses. In fact, you have too many. As you develop into adulthood, your brain has to prune away the weaker synapses in order to function efficiently. This is what we call synaptic pruning.  Let’s imagine your brain as a densely populated city with billions of buildings, each one connected to every other with its own separate road. This city looks like your brain when you were a baby – too many connections! In fact, this is what scientists call “hyperconnectivity” – and it is one chaotic place. This city needs some pruning!  But how do we know which synapses to get rid of and which to keep?  Imagine you’re driving to school, trying to navigate these tiny separate streets. It would be difficult at first but eventually you’d find the fastest route, and take that path each day. Your friends see how fast you get to school and decide to follow you.  Soon, all the kids in the neighborhood are taking the same road and there is a lot of traffic. The city needs to widen and strengthen this road to move all the traffic along efficiently.  The brain does the same thing with synapses between neurons that are sending lots of messages back and forth: the more the pathway is used, the stronger the connection!  And what happens to all those tiny streets you no longer use to get to school? We don’t need them anymore, so let’s remove that asphalt!  This is when synaptic pruning comes into play. Your brain adapts, removing the connections it isn’t using anymore.  So back to our coffee cup example: as the cells in your eyes send more and more messages to the visual processing center of your brain, those connections are strengthened. Meanwhile, the connections from your eyes to the auditory center of the brain are pruned away, so information from your eyes is processed only visually.  A big part of efficient synaptic pruning is keeping the proper balance. If not enough pruning occurs, the brain stays hyperconnected, as it was when you were a baby. This hyperconnectivity has been observed in some cases of autism, which could be related to the feeling of being overwhelmed when processing chaotic environments.
On the other hand, with too much pruning, communication within and between neural networks is disrupted. This results in impaired cognitive function - such as memory loss, often observed in Alzheimer’s Disease.  In a city with too much pruning, roadblocks pop up on your route to school, causing you to be late or making it impossible to get there. As it happens in the brain, this loss of synapses makes it hard to access memories and blocks certain paths of communication.
While the largest period of synaptic pruning is early in life, this process continues through adulthood.  So keep learning, and happy pruning!  Did you know each of our brains contain more than a quadrillion synapses?  That’s over a hundred thousand times the number of people on Earth!  And just think: you have all these connections to thank for your brain’s efficient processing!

Gabriel Anaya, Anthony Galante, Christine Han, Celine Schmidt
"Here is the beginning, and here is the end. But what happens in the middle? Our bodies took everything it could from this, and what was left was this...and a lot of it is fiber! Fiber is a general term for the carbohydrates within your food that your body can’t break down or absorb. Fiber can be found in many of the foods around us, including fruits, vegetables, and whole grains. Let’s take a look at the journey fiber takes through Billy’s digestive system and see why it is beneficial in our diets. Once Billy’s chewed sandwich makes its way down his esophagus and splashes into his stomach, the pool of acid there starts breaking down some of its components. The insoluble fibers soak up water and become bulky, while the soluble fibers begin to dissolve with water and become gel-like, or “viscous.” With all this extra volume, the fiber slows down the speed with which the food contents pass out of the stomach and into the small intestine, letting you feel fuller for longer. While traveling through all 23 feet of Billy’s small intestine, the fiber grows a little bulkier because of all the water it has attracted and absorbed along the way. This extra volume and viscosity of the fiber can help slow the breaking down and absorption of some nutrients into the body. But the fiber itself remains undigested and chemically unchanged! In the large intestine, the fiber finally meets its match. But it’s not you—the only things that stand a chance of digesting these strong fibers are the bacteria that live inside of you! Over 500 species of bacteria get to work digesting and fermenting the fiber that they meet in the large intestine. They can’t quite get to all of it, because some fibers are easier for them to digest than others. The water bulk in the fiber along with the extra volume from dead bacteria helps lubricate and speed along the movement of your colonic contents, making your bowel movements regular and easy: up, across, down, and out."

The Selfish Gene
Evan Fredriksen, Raffaele Gans-Pfister
Rickard: Hey Davithum! How’s it going, cousin?
Davithum: Rickard, Rickard! Good to see you! What brings you around my branch today?
Rickard: Well, I spoke to your mother, who told me that you might have some bananas to share with your ol cousin.
Davithum: Oh yeah? My mom said that? Yeah ummmm, I think I have some banana for you.  Here you go!
Rickard: Uhhh, what is this?
Davithum: That’s your share.
Rickard: Oh. Well your mother told me that I would be getting half a banana, and that’s what I have been expecting. Can I have half a banana?
Davithum: Let me explain something to you cuz; you mean a lot to me, ok? You’re my fur and blood! Me and you, we’ve got a lot in common! In fact, we’ve got 12.5% of our gene pool in common! But I’ve got children now. Fast but clear pan and zoom to wide shot towards children If I had enough bananas, I’d give each of you one of your own! But it just ain’t so, Rickard. And so I have to parcel them out according to how many of my genes you’re carrying. Davithum passes bananas to children.
Rickard: Well gee, Davithum. I thought we share a lot of really great memories together. Doesn’t that count for something?
Davithum: Of course it does! But it just doesn’t count for bananas. See, memories don’t cost me anything. We can sit around all day sharing memories. But when it comes to food, the welfare of my genes… I mean children! is at stake. When it comes to helping family, it’s all about the benefit x relatedness being greater than the cost. If this banana were less valuable to me, I would share more, but food is scarce! Likewise, if you were my brother, I would share more banana with you.
Rickard: So what about, your brother, Bandy-Legs?
Davithum: Bandy-Legs would say the same thing that I’m telling you! And our mom typically gives us one banana each, since we’re both carrying 50% of her genes. She gives my kids half a banana each, since they’ve got 25% of her genes, and since you’re her nephew, she would probably give you the same.
Rickard: But Bandy-Legs always gives me a lot of bananas!
Davithum: Well, Bandy-Legs is just trying to convince himself that he’s needed. He has loads of bananas to spare, so giving bananas away poses no risk to him and it helps him compensate for the fact that he doesn’t have any kids.  But it is what it is, Rickard. So, just take this banana with a smile, okay?
Rickard: Well, Davithum, I have to thank you for being straightforward with me. I guess when you ask me for bananas next, I’ll keep that principle in mind.
Davithum: I expect that you would, Rickard! 

Pan-zoom to plaque of family motto in needlepoint; “The Benefit times Relatedness must be Greater than the Cost.