If temperatures in the teens (or the 50s for the warmer climates) make you grumble, be glad you’re not a mammal living in the Arctic or around Antarctica. These animals face much colder air temperatures of -40 to -76 degrees Fahrenheit. While humans bundle up with thick sweaters and jackets to get through the winter cold, mammals such as seals, penguins and polar bears stay warm with blubber, feathers and fur. How do these materials keep the arctic chill out?
Credit: Getty Images
The ability of a material to insulate depends on how easily it lets heat pass through—a property called thermal conductivity. Fat has a low conductivity, which means it slows heat getting out and helps keep heat in. Marine mammals such as whales and seals have a layer of blubber beneath their skin. The blubber insulates their body so they don’t lose body heat while swimming in icy waters.
Feather and fur also have low thermal conductivity and are good for keeping warm. They also trap air—another substance with low thermal conductivity—creating an insulating layer of air around the body. If the animal feels cold, goose bumps fluff up their feathers or fur, which traps more air to slow down heat loss. This is why down jackets are so cozy: Down traps air, and this air layer insulates us.
You can test these materials out for yourself: This experiment in Advances in Physiological Education uses bubble wrap and vegetable shortening to demonstrate how fat and air work as insulators. Show us how your experiment turned out. Tweet a photo and use the hashtag #ISpyPhysiology.
Physiology Understanding (PhUn) Week takes physiology to the classroom through scientist-student outreach. This year’s PhUn Week wrapped up last Friday, but you can still continue the “PhUn” at home. Here’s an activity contributed by PhUn Week mentor Patricia A. Halpin, PhD:
This is a PhUn experiment that’s great to try with second to 10th graders (but adults may have fun with it, too!). Here, we test the hypothesis that performing exercise increases heart rate.
What You’ll Need:
- A stopwatch
- Paper and pen
- A clear space to perform exercise
Step 1: Record Your Resting Heart Rate.
Place your index and middle finger on the inside of your wrist or on your neck (in the soft area just below your jawline) to find your pulse. Count how many times your heart beats in 60 seconds (use your stopwatch to keep the time). Write down the number of beats you counted.
Step 2: Exercise.
Choose an exercise to perform, such as jogging in place, jumping jacks, push-ups or jumping rope. Set your stopwatch for three to five minutes and start your exercise.
Step 3: Record Your Post-Exercise Heart Rate.
Take your pulse the same way you did at the beginning of the experiment and write down your results. Compare the results. What did you find?
Your heart rate went up with exercise because more blood is pumped to the muscles you used during exercise. The blood brings needed oxygen to your cells so they can make energy for movement. With regular exercise, your heart rate will take less time to return to your resting heart rate. This is a sign of fitness. So, the next time you are exercising, take your resting heart rate and post-exercise heart rate and measure your fitness.
Patricia A. Halpin, PhD, is an assistant professor in the Biological Sciences Program at University of New Hampshire at Manchester.
Physiology Understanding (PhUn Week) takes physiology to the classroom through scientist-student outreach. Each year, more than 14,000 students learn about physiological concepts led through interactive lab experiments, such as this one as described by middle school science teacher Anne Joy:
As part of our PhUn Week activities, we talk to the students about genetics and DNA. If there’s one thing I’ve learned from teaching middle school students, it’s that they are very conscious of their looks, and they love to learn why they have the traits they do!
This is one of my favorite experiments because the students really like it. When physiologist Jessica Ibarra, PhD, visits our campus, the students get to actually extract and see the DNA of a strawberry. The students get so excited to see the DNA from something they are all familiar with. Try this at home and with your friends! All you’ll need is a resealable plastic bag, two strawberries, some water, plastic cups, a coffee filter, cold rubbing alcohol and a coffee stirrer.
At the end of the experiment, after seeing the DNA, and once all the “ooh”s and “ah”s have stopped, I like to show my students a three-foot piece of string to demonstrate the amount of genetic material that exists in every one of their cells. The questions that abound after this always get me excited about teaching science: “Does this work with other fruit?” “Can you do this with any living thing?” And, my all-time favorite, “Can I do this at home and show my family?” Absolutely! Extract away.
Anne Joy is a middle school teacher at Driscoll Middle School in San Antonio. She is a past Frontiers Fellow and past Frontiers Mentor Teacher. She has participated in PhUn Week activities with APS member Jessica Ibarra, PhD, for the past five years.
Jessica Ibarra, PhD
Back-to-school is an exciting time. It marks the start of another school and the start of the fall season. For some physiologists, the fall signifies it is time to plan and participate in K–12 science events, such as science day, health day, science fair judging and more.
One outreach activity gaining momentum among physiologists is Physiology Understanding (PhUn) Week. This November marks the 10th anniversary of PhUn Week, which takes scientists outside of the lab and into K–12 classrooms all across the country for the purpose of inspiring students with hands-on physiology activities.
There is no better (or easier) way to relate physiology to students’ lives and ignite curiosity than by exploring the senses (neurophysiology). But PhUn Week is not just for kids. Adults can get in on the action by learning more about physiology and trying some cool experiments, too.
Want to get in on the PhUn? Check out the September issue of “The Scientist,” dedicated to the sense of hearing and how the human ear translates sound into nervous impulses. In line with the theme of hearing, try an activity that makes sound come alive. For example, you can play a matching sound game or see sound waves or your pulse. Regardless of the physiology activity you select, make sure you have “PhUn” with science outreach.
Jessica M. Ibarra, PhD, is an assistant professor of biology at the University of the Incarnate Word in San Antonio.
If you’ve dropped a heavy object on your toe or slammed your finger in the door, you’ll notice that a sharp pain happens immediately, followed by a dull, throbbing ache later. Why the lag? It’s because two kinds of neurons—cells that relay signals between your body and brain—are working. The key difference between these neurons is how fast they transmit signals back to your brain, and the speed depends on whether the neuron is covered by a membrane called myelin.
Neurons are star-like shaped with long tendrils coming out. One finalist from The Physiological Society’s BioBake—a baking competition in which participants create physiology-themed baked goods—diagrammed a neuron out of gingerbread and Swiss rolls.
Credit: Amy Bradley / The Physiological Society
The star-shaped cookie is the neuron’s cell body which contains the proteins and machinery the neuron needs to work. Neurons receive signals— for instance, pain from your toe—at the cell body or at the dendrites, the points on the gingerbread cell body. The electrical signal travels down the axon, the cord portion with the Swiss rolls, and comes out the end of the axon to go onto the next neuron back to the brain. Neurons also pass signals from the brain to the body.
Many neurons have axons that are wrapped with layers of myelin—the Swiss rolls in this gingerbread neuron. The wrapped sections are spaced out like the Swiss rolls, with gaps in between. On a myelinated neuron, instead of passing down the entire length of the axon, the electrical signal hops from one gap to the next, going much faster. You will notice how much faster myelinated neurons are when you injure yourself. The sharp pain in your toe immediately after dropping a heavy object on it is from signals coming on myelinated neurons. The dull pain you feel later is from signals traveling unmyelinated neurons.
See what other physiological systems look like as baked goods. Check out this year’s BioBake entries and vote for your favorite one tomorrow and Friday.
Life is hectic. To keep you running, your body absorbs oxygen from the air you breathe and nutrients from the food you eat. How does your body make sure it’s getting the most it can to get you through your day?
Your body increases the surface that’s exposed to the air and food. In the lungs, oxygen is absorbed from the air into the blood in tiny sacs that cluster around the ends of the lung’s airways. A person’s lung has about 480 million of these tiny sacs. With so many little sacs, the total surface that oxygen is absorbed through is about the size of a tennis court.
The digestive tract has a different trick to increase surface. The inside surface of the intestines is fuzzy like toothbrush bristles. The fuzziness increases the portion of the intestines that’s in contact with the food, maximizing the amount of nutrients that can be absorbed.
Try out this concept of maximizing exposed surface to maximize absorption by making a soup stock. Traditional methods to making stocks recommend simmering the vegetables and meat in water for six to eight hours to extract all the flavors. However, dicing the vegetables into smaller pieces can produce the same flavor intensity with only two hours of cooking. How? Finely dicing increases the vegetables’ surface that is exposed to the water. More flavor molecules can come out, shortening the total time needed to extract the flavors.
Credit: Getty Images
For more details on the cooking experiment, view this Advances in Physiology Education article.
Credit: Getty Images
Moving food through your digestive system is not a simple process: Food does not just drop down into your stomach when you swallow. It’s actually a controlled journey coordinated by muscle cells that line the digestive tract. These cells are organized in two directions: crosswise, circling around the tract, and lengthwise, along the length of the tract.
The cells that circle the tract squeeze together behind the lump of swallowed food and relax in front of it. The muscle cells that run lengthwise do the opposite: They relax behind the food and squeeze together in front. Together, the actions narrow the tract behind the food and widen the section in front, pushing the food forward. This motion—called peristaltic movement—happens throughout the entire digestive tract, from the esophagus to the small and large intestines.
It’s easy to visualize how the tract narrows and widens with the help of the crosswise cells, but the action of the lengthwise cells can be trickier to imagine. A fun way to visualize this is by placing a marble inside a Chinese finger trap. Pulling the ends away from each other, like in the top image, narrows the tube and keeps the marble in place. Pushing the ends of the finger trap toward each other, like in the bottom image, widens the tube and allows the marble to pass through easily.
Chinese finger trap illustration. Credit: S. DiCarlo
When the muscle cells relax, it’s like pulling the ends of the finger trap, and when the cells squeeze together, it’s like pushing the ends. Learn more about this visual experiment in Advances in Physiological Education. Try it at home today.
– Maggie Kuo