Sunday, December 15, 2002

How Do Chicken And Turkey Have Dark And White Meat?

Ever wonder why turkey legs at Thanksgiving have dark meat, while the breast meat is white? The simple answer is because dark meat has more blood vessels giving food and oxygen to those areas than white meat does. But there is much more to the story. Both white and dark meat are skeletal muscles--the kind of muscles that help you move. Muscles contract or shorten, and relax or get longer in order to help you move. The meats are different kinds of skeletal muscles, leading to their different colors. There are three main groups of skeletal muscles: fast twitch glycolytic (GLY-CO-LIT-IC), fast twitch oxidative (OX-A-DATE-IVE) and slow twitch.

What do these words really mean? Well, the muscle groups are named for how they work. The fast twitch glycolytic muscles are powerful muscles that contract or work quickly, but they tire out quickly too. Sprinters who run short distances have trained their legs to use many of these quick working muscles. Muscles that tire out quickly would not be much use to marathon runners who need lots of energy for longperiods of time. Marathon runners have more of the fast twitch oxidative muscles. These muscles also contract or work quickly, but tire out slowly. The reason they do not tire out as quickly as the fast twitch glycolytic muscles is that they have large numbers of factories producing energy especially for them. These energy factories are called mitochondria (MI-TO-CON-DRI-A) and they make energy for cells.

So we have muscles that contract quickly, but tire quickly and muscles that do not tire quickly but use up a lot of energy. What do we do when we need a muscle to contract or work all the time without using up all of our energy? We do not want to be walking around as if we just ran a marathon all the time! Imagine how tired we would be! This is why we have the slow twitch muscles. The slow twitch muscles are like the ones in our back. They are always contracted so we can sit up straight in our chairs. These muscles contain lots of blood vessels so that they can always get food and do not have to produce lots of their own energy with the help of mitochondria. Our body needs all three types of muscles to work properly.

But what does this have to do with chicken and turkey? What type of muscles do you think make up light and dark meat? Let's think about here the dark meat is on a bird. It is found in the thighs and drumsticks. Chickens and turkeys are always on their feet and they do not need to move quickly. Dark meat is therefore a slow twitch muscle. What about white meat? Birds fly rather then walk to get away from something. So it would make sense that they would have fast twitch muscles to help them fly. That is why you find white meat in the breast of a bird. Although chickens cannot fly like turkeys can, they are relatives of birds that can fly and that is why they still have white meat or fast twitch muscle that move their wings.

Little Lion Experiment:

Can you identify where all the different types of muscles in your body are found? Run a sprint down your block and see which muscles you use. Run a around your block a couple of times and try to figure out which muscles you use. Those are your fast twitch muscles. Think about what muscles would be your slow twitch muscles.

Next time your mom or dad has a whole chicken or turkey for dinner ask them if you can identify the different types of muscles while they cut it up. Let your parents handle the knife to cut up the poultry and always wash your hands after handling raw poultry.

Monday, July 15, 2002

What is a Nerve?

A nerve is a cell that is specialized for sending and receiving information. Nerves make up the part of your body that tells your brain what your body is doing, called the peripheral nervous system. Your muscles, your stomach, and even your heart would not function if a nerve didn't send it directions from your brain.

Nerves carry signals like wires carry electricity. The long nerves in your body are like wires and the current would be the signals carried in the nerved. Charged atoms called ions carry nerve signals. The ions move in an out of the nerve cells in a wave-like manner down the nerve. This causes a charge to move down the nerve, this is how a nerve signal is carried. The longest nerve is the body is called the sciatic (si-at-tik) nerve and it is in your leg.

The sciatic nerve is a single cell that begins in your lower back by your spine and runs to the heel of your foot! Some nerves only send instructions from your brain to body parts; other nerves are there to report back to the brain on what is happening to your body. A nerve can actually sense changes in temperature, pressure, pain, or light, if the nerve has the right molecules. That's one exciting area of neuroscience (the study of brain stuff): neuroscientists are trying to figure out what types of molecules are found in each different nerve in your body. If you know what molecules are there, then you have a pretty good idea of what each nerve does.

When nerves are in your brain or spinal cord, we call them neurons instead. These neurons are part of the central nervous system. Neurons are a bit more complicated because instead of just sending information from one place to another, like a nerve, each neuron makes thousands of connections to other neurons. This means that the information can be sent backwards, forwards, sideways, even back in circles inside your head. We think that thinking has a lot to do with the complex pattern of information flowing in your brain. And when you think that these patterns in your brain are a million times more complex than the circuitry of the fastest supercomputer, your brain might just fry trying to comprehend its own complexity.

Consider this. Look up at the sky tonight. Try to count all the stars you can see without counting the same one twice. Now, imagine that each of these stars has nine planets like our solar system, and that each planet has nine moons orbiting it. Now imagine if you could draw lines connecting every moon on every planet to every other moon, creating some sort of a web across the sky. This "web" would look a little like the connections between all the neurons inside your brain.

However, your brain is even more complex than that! Your brain actually contains 10,000,000,000 connections between all the neurons, which is a network so complex, you would have to connect all the stars in the galaxy, including all those you can't see when you look up at the sky, to paint a picture like the complex web inside your head.

Saturday, June 15, 2002

Why Are The Basic Colors Different In Paint And Televisions?

The reason why this phenomenon occurs is because rules in mixing paints, inks, and dyes are not the same as those in mixing light. When a painter looks at their palette they can create any color with the three primary pigments: magenta, cyan, and yellow. It is not the same for a projection television. Colors such red, blue and green (called primary colors) are used to create all of the colors.

When the three primary colors of light are mixed, the intensities of the colored light are added. An example of this is where primary color light overlaps. When red light is added to green light, yellow light is formed. All colors can be made by the addition of different lights of the three primary colors. For example, red is 100% of red light and red light only. Blended colors like orange are 1 part green and 2 parts red light. Some color mixing is very complicated, like for instances gray is 3 parts red, 3 parts green and 1 part blue. The equal mixture of all three primary colors forms white light.

Our eyes are like television, in that they mix the primary colors of light to form an image. The human eye consists of two types of light receptors, rods and cones. Rods are used for light at low levels, like when you are in the dark. Rods in your eyes tell your brain to see things in black and white, so they perceive how much dim or intense the image is. Cones are what we use to see color. There are three types of cones: cones sensitive to red, blue and green. Based on how much each type of cone is stimulated due to the specific light, we perceive the color of light. For example if both red and green cones are stimulated, then we perceive yellow light. If only green cones are stimulated, we perceive it as green light. These three types of cones generate color vision.

Whereas primary colors are mixed in an additive manner, primary pigments are mixed in a subtractive manner. The primary pigments for mixing dyes used in coloring, photography, and printing are: magenta (light purplish pink), cyan (light blue) and yellow. The dyes of inks absorb certain colors. Any color that is not absorbed (subtracted) is the hue that we see. These dyes act as filters that subtract one or more colors. By varying the proportion of the colors in a mixture, a full range of colors can be produced. For example, the color yellow absorbs blue and reflects red and green. Magenta absorbs green and reflects red and blue. So, the mixture of yellow and magenta equals red (white minus blue minus green equals red). The mixture of all primary pigments is black, all light being absorbed.

In printing, the primary pigments are layered. A white layer is laid down first, followed by a yellow, magenta and cyan layer. Each pigment layer is carefully laid out to create a final image with the desired colors

Wednesday, May 15, 2002

What is Octane?

Most have heard the word octane used in regards to the hydrocarbon fuel gasoline. Octane is actually the generic name for molecules having eight carbon atoms and the chemical formula C8H18. More commonly, octane is used in reference to grades of gasoline. In this case, the numbers seen at the pump, 87, 89, and 93, refer to the fuel's octane number. So what vehicle owners are actually interested in knowing is "What is octane number?" Before getting into what octane number is and what it means to gasoline consumers, it is useful to have a basic understanding of how an engine works.

Vehicles that use gasoline have a four-stroke spark ignition engine. The first stroke is the induction stroke. The piston travels down the cylinder. A valve is opened allowing a mixture of fuel and air to enter into the cylinder. Next is the compression stroke. In this stage of the cycle, the valves are closed, and the piston travels back up the cylinder causing the air and fuel mixture to compress. When the piston has traveled to the top of the cylinder, the spark plug fires, causing the air-fuel mixture to ignite. The flame propagates through the mixture causing the temperature and pressure inside the cylinder to increase. The mixture expands forcing the piston down in the power stroke. Finally, the exhaust valve is opened and the piston travels back up the cylinder expelling any remaining gases in the exhaust stroke.

Under the high temperature and pressure conditions of the compression stroke, it is possible for the fuel-air mixture to ignite without the spark plug. This phenomenon is known as engine knock. Engine knocking is bad for a vehicle. It reduces a car's gas mileage and acceleration, creates wear and tear on parts, and in severe cases can lead to engine failure. Octane number is a rating that refers to a fuel's resistance to auto-ignition under specific engine conditions. Specifically, the octane number is the percentage of "octane" (2,2,4-trimethylpentane) blended with another chemical called pentane, that is required to achieve the same knocking characteristics as the fuel being tested. Since octane is very resistant to knocking and pentane knocks very easily, the higher the fuel's octane number the less likely it will cause engine knocking.

So why are there three different octane numbers? The different grades of gasoline are needed to match the different types of engines available. The most important engine characteristic to consider is the compression ratio: the ratio of the volume of the cylinder at the piston's lowest point and the volume at the piston's highest point. A car with a high compression ratio will perform better in terms of acceleration and power but will also subject the fuel to more severe temperature and pressure conditions, and will therefore require gasoline with a higher octane number. For example a Porsche 911 has a compression ratio of 11.3:1 and requires 93 octane number gasoline, while a Mercury Tracer has a ratio of 8:1 and requires 87. Consult your vehicle's owner's manual to determine the best grade of gasoline for your vehicle. You may be spending extra money on premium gasoline when you don't really need to.

Monday, April 15, 2002

Why Does Ice Float?

Now that winter has finally arrived here in Happy Valley and the ice outside is enough to keep even you in bed, have you ever wondered why it is that ice floats on top of water? Why is it that your solid ice cubes float to the top of your glass of water? Nearly every solid, if placed in its liquid form, will sink to the bottom. Luckily for us, the properties of water are different.

The meaning behind this mystery lies in the different properties of solid and liquid water. Unlike most other substances on Earth, the solid form of water floats on the liquid form. This is caused by the change in density, the amount of mass in a volume. With the exception of water, most substances on Earth become denser as they become colder. The solid ice will float because its density is lower than that of water. It is about 9% less dense than water. The denser water sinks to the bottom forcing the less dense ice to the surface.

What makes water molecules different from other molecules is that they attract each other in an organized fashion. As the water cools, the molecules begin to bind to each other, forming a hexagonal pattern. Water is at its densest point at 4C. After that point, the water molecules move very slowly and attract to each other. In most substances, the molecules are more tightly packed together in solid form. But in ice, the hexagonal pattern of the attracting water molecules leaves empty spaces. This is why your water expands when making ice cubes. The empty space between the hexagonal shapes makes the solid form less dense than the liquid form so that it floats to the top.

Thanks to this oddity of physics, the water in our oceans and seas remain in liquid state. If the solid form of ice happened to be denser than water, the ice would sink to the bottom. If this happened, the ice on the bottom would begin to freeze up toward the surface. Eventually, nearly all the water on Earth would become solid ice and never melt. Luckily, ice floats and remains on the surface so that the water underneath remains in liquid form.

This trait of physics also applies to other forms of water. "Heavy water" is used to cool nuclear reactors. An ice cube of heavy water will sink in ordinary water. Ordinary water contains two hydrogen atoms, but heavy water has two deuterium atoms. This causes a difference in weight. Deuterium atoms weigh about twice as much as hydrogen atoms and the extra mass of the deuterium adds enough weight so that an ice cube of heavy water sinks in ordinary water. But like ordinary water, an ice cube of heavy water will float to the top of a glass of heavy water.

So on your next icy Monday morning or tall glass of ice water, remember that density causes solid ice to float on liquid water.

Friday, March 15, 2002

Why Do I Get A Headache When I Eat Ice Cream?

I scream, you scream, we all scream for ice cream. Ouch! Some of us scream more than others. The University Creamery is a summertime hot spot , but for some people eating ice cream can be a painful experience. The ice cream headache or brain freeze as it is some times called occurs in about one in three people when they eat cold foods like ice cream or popsicles. The headache typically lasts from 15-30 seconds, but for some unlucky people the suffering can last up to five minutes.

You can't blame your mint chocolate chip because it's not the ice creams fault. Located on the roof of the mouth, near the back, there is a nerve center. Its job in part is to control the temperature of your brain. Like the thermostat in your house, this nerve center senses the temperature and can turn the heaters on or off. When the Peachy Paterno contacts the roof of your mouth, it cools down the nerve center making it think that your brain is dangerously cold.

The nerve center's thermostat reacts by turning the heaters on full blast. Blood vessels (tiny tubes that carry blood all over your body) in your head dilate or swell with extra warm blood that was meant to heat your brain. The extra pressure on your blood vessels causes the painful headache. Even though we call it brain freeze, the brain really isn't involved at all. The medical term for an ice cream headache is spheno palatine ganglioneuralgia. The condition is caused by a constriction in the blood vessels supplying the brain that lie just above the palate area.

The simplest way to avoid a brain freeze is to not put anything cold against the roof of your mouth. Let the food warm up a little in the front of your mouth before swallowing it down.

If you still end up with an ice cream headache there are several solutions you can try. The most common solution is to warm up your nerve center again. Pushing your tongue or your thumb against the roof of your mouth (and towards the back) will reheat the nerve center and turn off the headache. Other cures include: placing an ice cube against your inner wrist, eating a pinch of salt, and bending over to put your head below your heart.

Now you know how to beat that butterscotch, but you'll probably have to wait for summer to try it out. That's because most people don't get ice cream headaches unless the weather is warm. Good luck.

Friday, February 15, 2002

What is Malaria?

Malaria is an infectious disease characterized by fever, chills, nauseau, and general discomfort. It is caused by a single-celled parasite known as Plasmodium that infects and destroys red blood cells. Malaria is transmitted or passed by a mosquito that bites an infected individual, carrying the parasite to another person. More than 24 million people are infected with Plasmodium each year and 3 million people, mostly children, die from the disease.

Malaria has been around since the times of Ancient Egyptians. It used to be very widespread, effecting all of Africa, Asia, South America, southern Europe, and even North America. Cases as far north as Philadelphia used to be common occurrences. Today, the areas affected by malaria are somewhat smaller, mainly due to changes in the water systems in the early 1990s. Sub-Suharan Africa, Central America, and Southeast Asia are still hard hit areas.

There are three main ways to combat malaria. The first is to get rid of the mosquito population that transmits the parasite. This can be done by removing free-standing water that has accumulated in jars, tires, and other containers. Sewers can also be built to drain areas that have a lot of free-standing water. Spraying houses with insecticides, which are chemicals that kill insects without harming the environment or humans, can also terminate mosquitoes. A common spray that was widely used was DDT, although its use has recently been banned. The second way to combat malaria is to reduce the amount of exposure that humans have to mosquitoes. This includes wearing long sleeved shirts and pants when outside, sleeping under bed netting, using insect repellent, and staying indoors at dawn and dusk--the two times of the day when mosquitoes are the most active. Finally, if someone comes down with malaria there is a wide range of drugs that can be used to treat that individual. The most commonly used drug is chloroquine.

Unfortunately, many people who are administered chloroquine do not finish their recommended treatment. This, coupled with dramatic, but insufficient, worldwide efforts in the 1950s to spray areas with constant or endemic malaria, have resulted in the emergence of drug-resistant parasites and pesticide-resistant mosquitoes. This emergence has serious consequences for world health. Areas that are now malaria-free may experience a reoccurence of the disease. Luckily, researchers around the globe are focusing on finding new treatments for eradicating malaria.

Tuesday, January 15, 2002

What is Arteriosclerosis?

Arteriosclerosis is such a big word, but if we break down the word, maybe we can understand what it means. Arterio is what doctors call anything that deals with arteries, or the blood vessels that carry blood away from the heart; doctors use the word sclerosis when talking about something hardening. So when a doctor says the word arteriosclerosis, they mean hardening of the arteries. An artery affected with arteriosclerosis has fatty streaks, which are white or yellow lines down the middle of the artery. By age 25 most Americans have a fatty streak present in one or more of their major arteries. Fatty streaks are typically larger and more numerous in individuals with high cholesterol diets. Anything high in animal fat is considered to be high in cholesterol.

Cholesterol needs to be carried in the blood so that cells throughout the body can get the cholesterol for their membranes and steroid production (a cell's surface is called a membrane.). Cholesterol mixes with blood like oil mixes with water. In order for it to be carried in blood, it must be carried by a lipoprotein, which is a combination of a lipid (like fat) and a protein. The lipoprotein can carry cholesterol because one side of the molecule likes blood and the other likes cholesterol so a bunch of these lipoproteins surround the cholesterol while it is carried in the blood. The process of getting the cholesterol-carrying lipoprotein to the cells goes wrong with arteriosclerosis.

To understand how arteriosclerosis affects an artery we must first look at what makes up an artery. Going from where the blood is in the artery and moving out, arteries are composed of special skin cells, muscle cells, and connective tissue with skin cells. The skin cells in your arteries are not the same as the skin cells on your arm, but they do protect and form a barrier just like the skin on your arm. The skin cells inside your blood vessels, scientifically known as endothelial cells, serve as a sort of filter between the blood and the cells. Part of the way they filter the blood is by taking in only specific components of the blood.

One of these components is the cholesterol-carrying lipoprotein called low-density lipoprotein, or LDL for short. The endothelial cell pushes the cholesterol out of the other side of the cell, away from the blood side. Cholesterol then gets 'stuck' in between the skin and muscle layer. Neighboring cells and other cholesterol-carrying LDL molecules join the stuck cholesterol and the fatty streak grows. In addition to other cells and cholesterol-carrying LDL molecules, calcium can deposit in the fatty streaks. The presence of calcium causes the arteries to become hard and rigid. Typically our arteries are elastic and can stretch to help keep our blood pressure constant. When arteries become hard and cannot stretch, our blood pressure can increase. This is one of the reasons why doctors, nurses, and physician assistants keep track of our blood pressure so they can tell when it has gone up.

As the fatty streak grows and the artery becomes more and more rigid, the opening for the blood to move through become smaller and smaller. Sometimes total blockage can occur arteries. The fatty streaks can also burst when they become large and broken off parts can block small arteries. When arteries are blocked, a stroke or heart attack can occur. This is why arteriosclerosis is a major health concern in America. The arteries most prone to fatty streaks are the ones that supply blood to the heart (coronary arteries) and to the head.

For more information on arteriosclerosis, visit the Vascular Disease Foundation's website at