The Physiology of a Good Scare

Young scared couple is watching horror on TV.

Credit: iStock

With Halloween next week, you may be planning to head to a haunted house or cozy up on the couch with popcorn and a horror flick. Either way, you’re probably hoping for a good scare.

Enjoying the thrill of a scary movie or riding a rollercoaster isn’t the same as a real life-threatening situation, but your body doesn’t always know the difference. This is because the same senses are triggered when you’re startled in a safe environment as when there’s a genuinely fearful situation. Whether the fear is real or fake, your body leaps into action to prepare for whatever is going to unfold:

  • Your cardiovascular system pumps more blood and your heart beats faster.
  • Your brain sends adrenaline to your skeletal muscles, getting ready to move.
  • Your pupils dilate so you can see better.
  • Your digestive system slows down until the threat has passed.

Referred to as the “fight or flight” response, the human body functions similarly to how it would have thousands of years ago when faced literally with these two options: fight (for food or for your life, for example) or flight (run away).

During the physiological reaction to fear, scientists believe the brain stimulates the production of dopamine, a chemical that activates the pleasure center of the brain. Many people enjoy the feeling of a good scare and pursue other thrill-seeking behaviors to get the same “high.” Research suggests that thrill-seekers may have different brain chemistry than those who don’t enjoy a heart-pounding experience. If you don’t like to be scared, skip the tricks, enjoy the treats and remember to breathe deeply during this spooky season.

No matter where you fall on the scare scale, be safe this Halloween!

Erica Roth

The Young Qualities of Old Muscle

Senior Adults Taking Spin Class

Credit: iStock

Decline, decrease, deteriorate—all words associated with the aging process. Preventing “D” words is important to keep older people healthy. The loss of muscle is one of the most obvious age-related decreases we experience. Bulky muscles on a person that lifts a lot of weights or the sleek tone of a person that runs a lot of miles shows you that muscles of young people are amazing in their ability to change with the demands put on them. Scientists call this ability to change “plasticity.” When and why does muscle plasticity decline?

As individuals age, large muscle fibers that allow explosive types of movements, such as jumping or lifting a heavy weight, disappear more than small muscle fibers that allow slow, low-force movements such as grabbing a cup or adjusting posture. A recent Journal of Applied Physiology podcast discusses a research article that looked at small, medium and large muscle fibers from a group of subjects who were ages 87 to 90. At this age a substantial decline in strength is expected. However, the study showed that even though large muscle fibers are lost in old age, medium-sized muscle fibers become very strong for their size to compensate for that loss. The amount of force the medium-sized fibers could generate for their size was greater than muscle fibers from a group of young subjects and was similar to a world-class sprinting athlete. Therefore, the medium-sized fibers in the muscle of a very old group of subjects were plastic and adapted to the loss of bigger more explosive muscle fibers.

Future research is needed to determine if this plasticity is apparent in all old individuals or whether it was unique to this group that was still fairly active. Also, it is still unknown why some types of fibers keep this plasticity and others do not. Although older muscle does decline, decrease and deteriorate, plasticity appears to remain, which provides an interesting avenue to prevent the “D” words.

Ben MillerBenjamin Miller, PhD, is an associate professor in the department of Health and Exercise Science at Colorado State University. He co-directs the Translational Research in Aging and Chronic Disease (TRACD) Laboratory with Karyn Hamilton, PhD.

Keeping Up with the Highland Natives


Machu Picchu. Credit: Anne Crecelius

After spending three weeks getting to know the geography of Chile and making important connections with other academics, I treated myself to some tourist activity in Peru, Chile’s neighbor to the north. I met my mother in Lima, and we began a nine-day tour to visit the famous Incan sites of the Andes.

One major concern for travelers who visit mountainous regions is adjusting to a higher altitude. Upon our arrival in Cusco (11,200 feet above sea level), we quickly departed for a bit lower elevation in Ollantaytambo (9,160 feet) to allow our bodies to adjust to the high altitude. This type of itinerary is common for visitors to help minimize the chance of acute mountain sickness.

As we began to explore the Incan ruins of the Sacred Valley, it quickly became obvious that the altitude challenged most of the tourists (we were no exception!), but the many native tour guides seemed unaffected. Many native highlanders were also working as porters, not only hiking the famous Inca Trail, but carrying heavy loads with ease while doing so. I wondered how they made it look so easy.

Highland natives have long been studied in an attempt to understand how they have adapted to altitude over time and how their genes affect their adaptation. However, given the semi-remote locations where many of these populations live (the Andes, the Himalayas, etc.) and the small number of people participating in research studies, questions still remain.

A recent review article tried to answer the “nature vs. nurture” question as to why high-altitude natives are able to perform so well at high altitude. On the nature side, genes may regulate the ability for highlanders to maintain higher levels of oxygen in their blood. On the nurture side, it appears there are important changes in the lungs of high-altitude natives at very early ages that increase their efficiency in gas exchange in the lungs as adults. Gas exchange is one of the important factors in aerobic capacity (VO2) and the ability to perform work or exercise. Essentially, the natives develop greater breathing efficiency at high altitude, even when compared to lowlanders that have acclimatized or adjusted over a number of days.

Between catching my breath and thinking about the physiological challenges my body faced, I was able to enjoy the Peruvian landscapes and the rich Incan history. The highland natives of Peru are not only physiologically impressive but gracious hosts as well!

anne-crecelius-wanya-picchu-croppedThis post concludes a three-part series by physiologist Anne Crecelius, PhD, chronicling her summer of research and travels through South America. (Read part one and part two.) Crecelius is assistant professor at the University of Dayton.

Depression + Pregnancy = Diabetes?

Pregnant Frown

Credit: IStock

Morning sickness, swollen ankles and a growing belly are just a few of the many physiological changes that women experience during pregnancy. The changes  we can see are just the tip of the iceberg. Blood volume, bones, heart rate, skin and many other parts of a woman’s body function differently during pregnancy.

Pregnancy-related changes can sometimes lead to more serious health consequences for mother and baby during pregnancy and beyond. For example, gestational diabetes—a temporary condition in which the body can’t process sugar during pregnancy the way it usually does—can lead to a higher risk of other pregnancy complications, including having a large baby and increased chances of developing diabetes mellitus down the road. Now researchers have found a link between gestational diabetes and depression during pregnancy, a condition which affects an estimated 13 percent of moms-to-be.

A recent study showed that women who had more symptoms of depression in the first and second trimesters were at the greatest risk of developing gestational diabetes. The study also found that women who had gestational diabetes were four times more likely to develop postpartum depression after giving birth. Researchers say the relationship between the two conditions needs more study, but they think that the chemical changes in the brain that occur with depression during pregnancy may affect how we break down sugar.

These links emphasize the need to tune in to emotional shifts that many pregnant women experience. When crying jags and lack of energy lasts for more than two weeks or if symptoms get increasingly worse, it may be more than just pregnancy hormones at work. Women should also look out for the physical symptoms of depression which may include:

  • headaches
  • general aches and pains
  • stomach problems
  • loss of appetite (which may sometimes be mistaken for a side effect of morning sickness)

Now that doctors are learning more about the link between depression and gestational diabetes, they can monitor their patients more closely for both conditions during pregnancy. For more information about depression during and after pregnancy, visit the federal Office on Women’s Health website.

Erica Roth



What Blood Vessels Tell Us about Childhood Obesity

Little boy taking candy from jar

Credit: IStock

Did you know that blood vessels can “talk?” That’s right: Changes in the cells within blood vessels can communicate important information about the overall health of the cardiovascular system. The inside of blood vessels are lined endothelial cells—protective cells that form a tight barrier through which only certain substances such as water or glucose can enter. Endothelial cells also make many substances that keep the vessels healthy so that the heart can effectively pump blood to all of the tissues and organs. While strong, endothelial cells are also sensitive to changes or inflammation within the body. So, if the cells become damaged or stop functioning properly, it can indicate that there is a problem occurring elsewhere in the body.

Tuning in to the messages that blood vessels can reveal what’s going on inside our bodies, not just what’s happening within the vessels themselves.  For example, vessels can expose the effects of obesity and can help scientists discover links between body composition and the body’s response to food and sugar intake.

In a recent study published in the Journal of Pediatrics, researchers measured the endothelial function of teens ages 12–19 years for clues into the relationship between obesity and how the body handled sugar. By conducting the study in teenagers with a wide range of body compositions—from normal weight to obese—they were able to make conclusions about blood vessel health, how it relates to obesity, and how obesity contributes to the development of problems in the body’s ability to handle sugar properly. They found that obese young people had higher levels of endothelial cell damage that correlated with the body’s inability to handle sugar. Indeed, in this example, the endothelial cells in the vessels “spoke” to the researchers about the health of the study participants.

This study also underscores the importance of preventing childhood obesity, which has been linked to a reduction in the body’s ability to regulate the amount of sugar in the blood. Limiting the intake of processed, high-sugar food and drinks is a great start. The second step is to increase physical activity during childhood and adolescent years. These habits, when started early, may carry into adulthood and lead to a healthier life. September is Childhood Obesity Awareness Month. Find more tips for helping kids maintain a healthy weight on the CDC website.

audrey-vasauskasAudrey A. Vasauskas, PhD, is an assistant professor of physiology at the Alabama College of Osteopathic Medicine.

Shhh … I’m Hibernating!

Bear nest

Man crawling out of uninhabited bear hibernating den (not recommended). Credit: IStock

As the days grow shorter, many animals, such as bats, bears and bees, begin getting ready to hibernate. It’s a process that allows animals to spend the winter months conserving energy by reducing metabolism, oxygen consumption and body temperature. So why don’t humans do it, too? Well, a new study suggests that some humans—specifically those with chronic fatigue syndrome (CFS), which affects more than 2.5 million people in the U.S.—may be doing something similar to hibernating.

People with chronic fatigue syndrome experience extreme fatigue. But this is not your run-of-the-mill kind of post-holiday exhaustion. It is severe fatigue that does not get better, even with sleep. People with CFS may also experience issues related to memory and headaches. It’s not clear why people develop the disorder, but some theories point to infections, exposure to chemicals or stress as possible causes.

The new study, published in the Proceedings of the National Academies of Science, looked at specific molecules (metabolites) that are byproducts of energy production (metabolism) in the blood of people who have CFS and healthy people who do not have the disease. The researchers found that people with the condition had 80 percent fewer metabolites compared to the healthy control subjects. Those with chronic fatigue syndrome also had some impairment in the way their metabolism functioned. The findings suggest a less active metabolism in people with CFS similar to metabolic activity seen in animals that hibernate. Reduction in metabolic state is thought to be a defensive strategy all humans can use to cope with situations in which environmental or other stressors are present. The problem for people with CFS is that this defense mechanism stays turned on, slowing metabolism—and draining energy—on an ongoing basis.

What’s great about this study is that researchers and clinicians finally have a set of chemical markers in the blood that they can use to test people for CFS. The hope is that by understanding what’s going wrong, metabolically speaking, a treatment can be developed.

Karen SweazeaKaren Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.

What Happens during Heat Stroke and How to Prevent It


Young kids are at increased risk of heat stroke. Credit: IStock

Temperatures in July and August 2016 were the hottest ever recorded on the planet and much of the U.S. is still struggling with a heat wave. Hundreds of heat-related deaths occur in the U.S. each year, and these rates are on the rise. Awareness of when the body is losing the ability to deal with heat and seeking treatment for heat illness and dehydration are key to reducing heat stroke-related deaths. So it’s extremely important to understand the causes and symptoms of heat illnesses, such as heat stroke, and who’s at risk.

Under normal physiologic conditions, the human body can counteract overheating by sweating and other means. Heat illness occurs when the body is overwhelmed by the heat and can no longer maintain its temperature. Heat stroke is the most dangerous type of heat illness, though heat fatigue, heat cramps and heat exhaustion can also occur. These conditions can have a variety of effects on the body, blood flow and a person’s mental capacity. For example, heat stress with mild to moderate dehydration can result in loss of blood flow to the brain and the inability to stay upright.

Who’s at Risk of Heat Stroke and How to Prevent It

Heat stroke can develop in people of any age or health status, but the sedentary elderly, very young people and individuals with chronic disease such as heart disease have a significantly higher risk of having one. People who take certain medications, drink alcohol, are very overweight or who have poor blood circulation (such as those with diabetes and heart disease) or reduced sweat production due to aging are also at an increased risk. Prolonged, intense exercise in a hot environment without proper hydration can cause a heat stroke during heat waves, even among young and healthy people.

The most effective ways to prevent heat stroke is to ensure that high-risk populations:

  • have access to air conditioning or a cool environment with air flow;
  • dress comfortably in layers that can be removed as the temperature rises;
  • stay hydrated by consuming water, fruits and vegetables (such as watermelon, tomatoes, lettuce, pineapple, cranberries and oranges), herbal tea, etc; and
  • understand the signs and symptoms of heat stroke.

People may be developing heat illness if they appear confused or faint, are not sweating or have flushed skin after being exposed to the heat. Any individual experiencing these symptoms should be removed from the heat, offered fluids and examined for the possibility of heat illness or heat stroke.


Robert Carter, III, PhD, MPH, FACSM, is an adjunct professor of emergency medicine at the University of Texas Health Science Center at San Antonio and the product manager for medical simulation at the Program Executive Office for Simulation, Training and Instrumentation in Orlando.

What Is Physiology?…and Why You Should Care


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Physiology provides an explanation of life, and everyone—not just doctors and scientists—would benefit from understanding some essential physiological concepts. But to learn how physiology applies to everyday life, you must first understand what it is.

Physiology is the study of how living organisms function in sickness and in health. Physiologists study functions that may take place on a small scale, such as in molecules or individual cells, or in whole animals such as humans. Physiological research has led to breakthroughs in our understanding of how we move, reproduce, gain and lose weight, live, thrive, die and much more. Because of this, a strong grasp of physiology is imperative for doctors and other health care providers who see patients and treat disease.

But it’s also important for the average person to have an understanding of physiology. It can help patients understand why their doctor recommends that they work out, eat less salt or take a certain medicine. Physiology can also inform our everyday decisions related to diet, exercise and sleep.

Integrative physiologists, like me, study how the body responds to stimuli such as exercise. Some examples of the type of functions we study include:

  • How oxygen supports metabolism, how its use determines how many calories we “burn” at rest and during exercise and how it can help determine a person’s cardiorespiratory fitness level.
  • How the body controls blood pressure, what happens to blood pressure when we exercise, and what can be done to lower blood pressure and prevent it from getting too high.
  • The critical role of sodium (salt) in regulating fluid levels in the body and how it can raise blood pressure and damage tissues when too much is consumed.
  • The importance of blood flow regulation in delivering nutrients and oxygen to the working muscles at rest and during exercise, which is critical for athletes and for slowing down age-related declines in physical function.

Key physiology concepts provide the framework for addressing these issues, and there is still so much to learn and explore!

To quote one of physiology’s forefathers, Arthur C. Guyton, “Physiology is indeed an explanation of life. What other subject matter is more fascinating, more exciting, more beautiful than the subject of life?” I agree (though I may be biased). But whether you’re intrigued by physiology or not, the insights into health and disease that it uncovers hold a benefit for us all.

william-farquharWilliam B. Farquhar, PhD, is a professor and chair in the department of kinesiology and applied physiology at the University of Delaware. He is a Fellow of the American College of Sports Medicine and member of the American Physiological Society.

A 10,000-Foot View from the ALMA Observatory in Atacama

Atacama Telescope

Rare clouds drift behind a telescope at the ALMA Observatory in Chile.

After fulfilling the main purpose of our trip—to build relationships with universities in Santiago, the capital city of Chile—we headed north to the Atacama Desert, the driest non-polar desert in the world.  The small town of San Pedro de Atacama serves as a starting point for adventure travelers looking to experience all this beautiful landscape has to offer. It is also the closest town to the Atacama Large Millimeter/submillimeter Array (ALMA)—a multi-national space observatory that seeks to understand our cosmic origins.

My colleagues and I boarded a public tour bus to the ALMA operations center. The on-board safety video once again put physiology front and center as it discussed a reality that locals here deal with every day: the effects of altitude on the human body.

San Pedro, and most of the Atacama Desert, is located at around 8,000 feet above sea level. The ALMA control center sits above the town at around 10,000 feet. Most impressively, the radio telescopes that make the observations are located on a plateau at 16,000 feet high. For comparison, Mount Whitney, the highest mountain in the continental U.S., is 14,505 feet above sea level.

UV Warning Atacama

A warning to ALMA visitors about prolonged UV exposure.

Spending time at high altitudes can have an impact on the cardiovascular and respiratory systems. The increased ultraviolet exposure is significant, and ALMA visitors (even just to the control center) are cautioned against spending prolonged periods in the sun and are advised to wear sunscreen and protective clothing. The extremely arid Atacama Desert also challenges the body’s ability to maintain proper hydration, so water is frequently provided to visitors.

The safety video explained that at 10,000 feet, the control center is considered “moderate” altitude that most people can tolerate well. However, we learned that any visitors to the actual telescopes—which the general public is not allowed to visit—must go through a medical screening that includes taking vital signs (heart rate, blood pressure, blood oxygenation) and assessing signs and symptoms of altitude sickness (dizziness, headaches, nausea). Telescope visitors must also spend a minimum of one night getting used to the high elevation (acclimatizing) in Calama (the town where the nearest airport is) or San Pedro to prepare the body for this challenging environment. They are also given supplemental oxygen to help prevent any altitude-related issues and to allow them to perform physical tasks that might otherwise be too difficult.

All of these physiological challenges of visiting and working at ALMA ultimately are what makes it perfectly suited for its main purpose, observing our skies. Dryness, high altitude, no clouds and minimal light or radio pollution from nearby sparsely populated towns (it’s not easy to live in the Atacama!) are perfect conditions for the ALMA scientists to try to solve important astronomical mysteries.

Anne Crecelius - Chile

Crecelius puts safety first during her visit to the ALMA Observatory.

This post is part two of a three-part series by physiologist Anne Crecelius, PhD, chronicling her summer of research and travels through South America. (Read part one here.) Crecelius is assistant professor at the University of Dayton.

Physiology for the Armchair Scientist


PIO Homepage Large


Want to learn more about physiology without going back to school for a PhD? Check out The website, hosted by the American Physiological Society, goes in-depth to explain the multi-faceted field of physiology to nonscientists. In addition to examining hot and emerging areas of research such as brain physiology, obesity and exercise, we look at the how the body’s systems work individually and together to keep us going every day.

Our reference library houses quizzes that will test your physiology smarts, dozens of podcasts on cool research findings, a library of vintage equipment dating as far back as the 1870s and much more. We also feature timelines that highlight important milestones and people in the history of physiology.

We hope the site will serve as a helpful and informative resource about our area of research. Check back often for new information. And if you have questions you’d like us to address, let us know!

Stacy Brooks