When Vampires Attack: How Your Body Reacts to Extreme Blood Loss

Portrait of a little boy dressed up as halloween vampire

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It’s Halloween and the number of vampire attacks in your neighborhood may be on the rise! What would happen to your body if you were unlucky enough to be the victim of a blood-sucking vampire?

The average adult has about 1 to 1.5 gallons of blood circulating in their body. Maintaining this amount of blood is very important—proper blood volume helps keep your blood pressure at a steady level and moves the right amount of blood around your body. As your heart pumps blood through your blood vessels, the blood carries nutrients and oxygen to your organs so that they have energy to do their jobs. The blood also takes away the waste that your organs produce.

When you lose a large amount of blood very rapidly (such as during a vampire attack) your blood pressure drops quickly. This is similar to having a punctured bicycle tire. As the air escapes through the hole, there is less pressure in your tire. During an episode of significant blood loss, your body starts to take action to increase blood volume and blood pressure:

  • Sensors called baroreceptors detect the decrease in blood pressure and cause your heart to pump faster and your blood vessels to narrow (constrict).
  • Your body releases chemicals called catecholamines, which also cause your heart to pump faster and your blood vessels to constrict.
  • Your pituitary gland releases a chemical called vasopressin. Vasopressin constricts blood vessels and helps your body hold on to as much water as possible by decreasing the amount of urine you produce.

When blood vessels constrict, the blood inside the vessels push against the sides of the vessel more, causing blood pressure to increase. Increased blood pressure reduces the amount of blood needed to fill your vessels.

If these actions are unable to restore your blood pressure, you can go into shock. Shock occurs when your blood pressure is so low that not enough blood is getting to your organs. In a state of shock, your heart, liver, kidneys and brain can’t function properly and they start to die from lack of oxygen and nutrients. You’ll eventually lose consciousness if you don’t get urgent medical attention—typically with intravenous fluids—to raise your blood pressure and increase circulation.

If you choose to trick or treat this Halloween, stay safe. Carry some garlic with you to ward off those pesky vampires and dial 911 ASAP if you have a run-in with a fanged stranger.

Dao Ho, PhD

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center. The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.

Yoga + Deep Breathing = A Calmer You

Relaxing Together in a Yoga Class

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“I’m not flexible enough to do yoga!” In my 12 years as a yoga instructor, this is the excuse I have heard most often for why people aren’t practicing yoga. My initial response is usually, “That’s exactly why you should be practicing yoga!” However, I am also an assistant professor of physiology, and I know that the benefits of yoga go far beyond flexibility. Participating in yoga regularly imparts a number of benefits— from weight management to stress reduction—to our physical and mental health.

One very important side benefit of yoga that is linked to both physical and mental health is breath control. Slow, deep, conscious abdominal (belly) breathing, especially during difficult poses, trains us to use the same type of breathing in challenging scenarios off the mat, such as giving a presentation, taking an exam or performing a difficult task.

Why do deep, yogic belly breaths help us through stressful situations? Recent studies suggest that this type of breathing can decrease firing of the sympathetic nervous system while increasing activity of the parasympathetic nervous system. The spike in heart rate and blood pressure, sweaty palms and voice tremors you might experience when you speak in front of an audience, for example, are due to activation of your sympathetic nervous system—the “fight-or-flight” response. This nervous response is great if you are running from a bear in the woods. But in real life these changes can lead to short-term memory problems and high anxiety levels that may interfere with giving a presentation or taking a test.

If you approach stressful situations with abdominal breaths, however, you help shut down the fight-or-flight reaction and increase the parasympathetic nervous response. Called a relaxation response, your heart rate slows down and your blood pressure returns to normal. Once you’re relaxed, you can approach the task at hand in a calm, collected way.

Many types of yoga incorporate physical movements with deep abdominal breathing. The physical demands of these movements have the potential to cause the fight-or-flight response, but by combining these poses with yogic breathing, we learn how to control our breath in seemingly stressful situations. So the next time someone tells me they are not flexible enough to do yoga I will ask them if they can take a deep breath. If they say yes, then I know they are ready to go!

September is National Yoga Month. Check out a yoga class or festival near you.

Audrey Vasauskas

Putting Out Fires Hurts Firefighters’ Hearts

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As the temperature outside rises, our bodies make adjustments to keep our internal temperature constant to prevent us from overheating through a process called thermoregulation. This includes bodily functions such as sweating and widening of the blood vessels (vasodilation). When we sweat, perspiration evaporates from our skin to cool us down. When the blood vessels under our skin widen, our heart pumps more blood to our skin, which releases more heat from our inner body.

Our bodies are constantly working to hold a steady core temperature around 98-100 degrees Fahrenheit (F). This allows our organs to function properly. But when the temperature outside is extremely hot, our temperature can start to rise. A person with a body temperature above 104 degrees can develop heat stroke. This can cause dizziness, difficulty breathing, confusion, seizures or loss of consciousness. Brain and heart damage—sometimes permanent—can occur when body temperature climbs above 107 degrees F.

Too much summer heat can be unhealthy for everyone, but it can be especially dangerous to firefighters. The incidence of fires increases in the U. S. during the summer months. Firefighters fight almost twice as many fires in the summer compared to the rest of the year. On top of dealing with the extreme heat (sometimes over 700 degrees F!), these first responders face extreme physical exertion, mental stress and smoke inhalation on the job. All of these factors together can place firefighters in immediate danger of heat exhaustion, heatstroke and heart problems. In fact, firefighters are up to 136 times more likely to die from coronary artery or heart disease during or soon after they suppress a fire.

In a study published in Circulation last month, researchers may have uncovered several reasons why putting out fires puts firefighters at risk for heart disease. They discovered that a single, 20-minute session of fire simulation training—where healthy firefighters were exposed to physical activity in the extreme heat (about 755 degrees F)—was enough to injure their blood vessels, even though the firefighters’ core body temperature never reached above 101 degrees F. The problem: Although the firefighters’ bodies did keep their core temperature within a healthy range, their blood vessels did not relax properly immediately after the training. Also, as a result of the training, the firefighters’ blood clotted more easily. Damaged blood vessels and increased clotting of the blood can be very harmful to the heart and sometimes can lead to a heart attack.

This research shows us that even when we are able to keep our body temperature from getting too high, there are hidden dangers of being physically active in extremely hot temperatures. So keep your heart healthy this summer and don’t overexert yourself while outdoors!

Dao Ho, PhD

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center. The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.

A Healthy Diet: A Prescription for a Healthy Life!

food pyramid pie chart

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We have all heard the phrase “You are what you eat.” Not only is there a lot of truth in that little saying, it is also a great reminder for us to be aware of everything we put into our bodies. Everything we eat and drink has an effect on our being and our physical and mental health depends on proper nutrition.

Most people know that nutrition means getting the right amount of nutrients to fuel our bodies and brains. But the difference between the types of nutrients can be less clear.

Nutrients are divided into three categories: micronutrients, macronutrients and water.

Micronutrients are vitamins, minerals and substances such as sodium and potassium called electrolytes. They are essential for growth, development and normal cellular activities. A wide variety of fruits, vegetables and animal products such as meat and dairy are rich in micronutrients.

Macronutrients include carbohydrates (sugar and starches), protein and fats. Macronutrients are extremely important because they give us the calories we need to produce energy. Each person needs a different amount of macronutrients depending on their body size, body composition and level of physical activity. This last point—activity level—is key. We often eat and drink far too many calories for our body’s needs and store the extra calories as fat. The excess fat can become a big problem, causing inflammation, problems with metabolism and cardiovascular issues.

Water is important for maintaining your body’s fluid balance and for functions such as digestion, circulation and body temperature. We also need water to carry nutrients throughout our body and to energize our muscles.

The lack of proper nutrition is still an issue in areas of the U.S. and other Western countries. However, consuming too many calories without enough nutrients is also a critical health problem in the developed world. In fact, the definition of “malnutrition” has been updated to include overnutrition. The expanded definition of malnutrition highlights the serious threat that overnutrition and obesity have on human health.

If you want to learn more about how to fit better nutrition into your life, visit the U.S. Department of Agriculture’s Choose My Plate website. This tool can help jump-start your nutrition knowledge and get you on your way to feeling great.

Audrey Vasauskas

 

Walking and the Brain, Aromatherapy for Horses and a Whole Lot More!

Physiology, the study of function from microscopic cells to complete organ systems, encompasses a wide range of fascinating topics. The annual Experimental Biology (EB) meeting is a showcase for thousands of researchers studying humans and animals alike. Check out some of the research presented at last month’s meeting in Chicago:

Close up shot of runner's shoes

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Most people know that walking is good for heart health, weight management and flexibility. New research from New Mexico Highlands University reveals how your brain also benefits from walking. Each step you take sends pressure waves through your arteries and increases blood flow—and oxygen—to the brain. The researchers found that running also had a beneficial effect on blood flow, while sports like cycling that don’t involve foot impact were less likely to make a significant difference.

Dressage test

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Do you like the calming scent of lavender when the pressure’s turned up? Turns out, you’re not alone. Research out of Albion College studied the effects of aromatherapy on horses. Much like people, competition horses get stressed out when they’re transported from their home to an unfamiliar venue. Stress reduction therapies are highly regulated in competition horses, and non-medicinal treatments could go a long way to calm the animals before they perform. The researcher found that stress hormone levels dropped significantly among trailered horses that were exposed to lavender aromatherapy when compared to distilled water mist.

Two women rowing on a lake

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Olympic-caliber athletes appear to be the picture of strength and power. But new research suggests that high-intensity workouts without a proper recovery period could interfere with optimum bone health. A study of female Olympic rowers from Canada’s Brock University showed that the levels of a protein that stops bone mineral loss dropped during extended periods of heavy training. Bone mineral loss weakens the bones and increases the risk of stress fractures and osteoporosis.

These studies just scratched the surface of all the top-notch physiology research presented at EB. Read more highlights from this year’s meeting:

Why vitamin A and a high-fat diet don’t mix

The role of immune cells in the cause—and treatment of—preeclampsia

How an ice bag on the face can help treat severe blood loss

An “exercise pill” may be in our future

How orange essential oil reduces PTSD symptoms

 

Erica Roth

When’s the Best Time to Eat? Your Body Clock Knows

 

Two teenager girls, sisters, eats fastfood on the street

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The American Heart Association recently released a statement suggesting that when and how often you eat could affect your risk for developing heart disease and stroke. Until now, the focus on diet has been primarily about how much and what you eat. This news—that the time of day you eat may also be important—could change the way people are able to manage their health.

Our bodies have natural daily patterns called circadian rhythms that occur roughly over a 24-hour cycle. Many biological processes are driven by circadian rhythms, including when you go to sleep and wake up, your body temperature, heart rate, blood pressure and the release of various hormones. A “master clock,” a tiny group of cells called the suprachiasmatic nucleus (SCN), located in the hypothalamus area of the brain manages circadian rhythms. This master clock is mostly controlled by changes in light.

Every cell in the body also has its own internal clock called a “peripheral clock.” Peripheral clocks make sure all of the cells’ functions are coordinated with the master clock. Animal studies show us the importance of keeping peripheral clocks in sync with the brain’s master clock. For example, when the peripheral clock in a mouse’s heart is disrupted, the mouse develops heart failure and dies at a much younger age than normal mice.

Unlike the master clock, peripheral clocks are more responsive to the availability of food than changes in light. As a result, eating at the “wrong” time of day could shift the rhythms of the peripheral clocks so they are out of sync with the master clock. For example, shift workers who work in the middle of the night are active when they would normally be asleep and eat at times when their body doesn’t expect food. They are at much greater risk for being overweight, becoming insulin resistant and developing cardiovascular disease because their master and peripheral clocks are likely to be out of sync.

Research in mice has shown that if they consume a high-fat meal at the end of their active period (the equivalent of a high-fat dinner for humans) they gain more weight, develop insulin resistance and have impaired cardiac function compared to mice that eat the same high-fat meal at the beginning of their active phase (breakfast).

Studies in people suggest that eating meals late in the day is linked to negative health effects, but a direct relationship has not been shown. Nevertheless, if when you eat is just as important as what you eat, it might not hurt to eat your larger meals earlier in the day if you can.

 

John Chatham

John Chatham, DPhil, is a professor of pathology and director of the Division of Molecular and Cellular Pathology at the University of Alabama at Birmingham.

Ida Henrietta Hyde: A Trailblazer in Physiology

 

hyde1

Ida Hyde at Heidelberg University, 1896.

March is Women’s History Month, a time when women who have challenged—and continue to challenge—traditional roles are celebrated. This month, the I Spy Physiology blog will introduce you to several female physiologists, starting with the first female member of APS, Ida Henrietta Hyde.

Ida Henrietta Hyde was born in 1857 in Davenport, Iowa, the daughter of German immigrants. She went to public school and took jobs as a dressmaker and milliner (a person who designs or sells women’s hats) to help support her family. After reading a book about natural science, she became fascinated with biology. This newfound interest in life sciences inspired her to save as much of her salary as possible so that she could go to college someday.

In 1882, Hyde started classes at the University of Illinois at Champaign but was soon forced to withdraw to help care for her sickly brother. During that time, she taught elementary school in Chicago, where she was instrumental in introducing a science curriculum to the Chicago public school system.

By the late 1880s, Hyde was able to return to college and went on to earn a degree in biological sciences from Cornell University in Ithaca, N.Y. She worked in research at the Marine Biological Laboratory at Woods Hole in Massachusetts before traveling to Europe on a fellowship to pursue a PhD—something women were rarely able to do. Hyde’s early work centered on the neurophysiology of vertebrates and invertebrates, but she also conducted research in cardiology. Her article “The Effect of Distention of the Ventricle on the Flow of Blood through the Walls of the Heart” was published in the first issue of the American Journal of Physiology in 1898.

Women's history month design with multicultural hands

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By 1902, Hyde was back in the U.S. and had become an associate professor of physiology at the University of Kansas. She eventually became head of the department and was nominated for APS membership in 1902. She was the only female member of APS until 1913. Today, APS is proud to count more than 3,100 women as members.

APS membership was just one of Hyde’s many accomplishments as a scientist and physiologist. Her landmark achievements paved the way for many more women who follow in her footsteps. Read more about her in The Physiologist.

Erica Roth

Go Ahead, Wear Your Heart on Your Sleeve!

Jousting Competition

A jousting knight wears his heart on his sleeve. Credit: iStock

In medieval times, a jousting knight would wear the colors of the lady he was courting tied around his arm. Hence, the phrase “Wear your heart on your sleeve” was born. Today, we use this romantic phrase to describe someone who expresses their emotions openly. How applicable that ancient phrase really is to maintaining a healthy heart!

In a landmark paper, a group of scientists discussed how stress and social interactions with others affected the health of the heart. It is well-known that stress is a major factor in the development of heart disease. This is because stress is a double whammy: It activates the “fight-or-flight” nervous response, and it causes inflammation in the cells that line blood vessels. Both of these events can damage blood vessels in the heart.

Research shows that positive social interaction expressing emotion is important for heart health. Support from a spouse or partner, friends or other groups can reduce stress and help you stick to a healthy diet and exercise program to minimize your risks.

Heart disease is the leading cause of death worldwide, with annual deaths creeping up to 24 million. Reducing stress and anxiety is an important aspect of keeping your heart healthy. Exercise, yoga, meditation and even deep breathing can promote a sense of calm when tensions mount. Try running or yoga with a friend or join an exercise class to keep you on track for a healthy heart. Go ahead, wear your heart on your sleeve—it’s good for you!

February is American Heart Month. You can find more information about keeping your ticker ticking on the American Heart Association’s website.

Audrey Vasauskas

Microvesicles and Blood Vessels and Exercise, Oh My!

Swimming

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The American Heart Association recommends that adults get at least 30 minutes of endurance exercise every day to keep your heart, lungs, and circulatory system healthy. A daily workout can help reduce your risk of developing diseases such as diabetes, heart disease and stroke. Endurance exercise is basically any activity that increases your breathing and heart rate for an extended period of time. Examples include:

  • brisk walking
  • jogging
  • dancing
  • biking
  • swimming
  • climbing stairs

During exercise, your blood vessels expand (dilate), increasing blood flow, and delivering more oxygen to your working muscles. Over time, exercise helps your blood vessels become more flexible. This flexibility allows the vessels to dilate more quickly to deliver blood and oxygen to your muscles. Long-term endurance exercise also increases the number of small blood vessels (capillaries) in your body. All of these things help carry more oxygen to your organs and remove waste more quickly. As a result, you can enjoy better athletic performance, such as being able to jog farther, run faster or swim longer distances.

A recent study in the American Journal of Physiology—Heart and Circulatory Physiology showed that endurance activity may help blood vessels grow by increasing the number of microvesicles in your blood. Microvesicles are small particles that are shed into your blood from all types of cells in your body. When volunteers in the study rode a stationary bicycle, they produced more microvesicles than when they were sitting and resting. The number increased even more when they pedaled faster. The researchers then added the volunteers’ microvesicles to endothelial cells—a type of cell that lines the blood vessels and is responsible for expanding and contracting them. They found that microvesicles caused endothelial cells to grow twice as fast. In other words, when you exercise, the number of microvesicles increases, which in turn helps your blood vessels grow.

Now you know why exercise builds a better circulatory system, so get moving!

Dao Ho, PhD

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center. The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.

Are Cross-Country Skiers Premier Athletes?

 

Cross Country Skiing Couple

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With winter upon us, it is a good reminder that cold weather is not an excuse for inactivity. Athletes from cold-weather climates, such as the Nordic countries, are not content to stay indoors during winter. In fact, cross-country skiers from these colder climates might be considered the premier human aerobic athletes.

Although some picture cross-country skiing as slowly shuffling along at a leisurely pace, the reality of competition is much different. For example, the winner of the 50 km (31 miles) freestyle at the 2014 Winter Olympics finished the race in less than one hour and 47 minutes. That’s longer than a marathon but finished in less time. And these races typically go uphill for 50 percent of the time!

Physiologically, skiing is interesting from many perspectives. The biomechanics of skiing are interesting because the arm and leg movements must be coordinated to efficiently move forward. The whole-body nature of skiing makes the physiology fascinating to study. Cross-country skiing puts large demands on the heart to deliver blood and oxygen to exercising muscle. This challenge is greater than for running or cycling (which engages only the legs) because both the arms and the legs need to work with skiing.

The amount of blood going to the arms versus the legs constantly changes, too. These changes are based on the hundreds of technique transitions needed to cross the varying terrain during a race. The great physical endurance required improves the ability of cross-country skiers’ muscles to use oxygen. These athletes have some of the highest levels of oxygen consumption (VO2max) on record. Legendary physiologist Bengt Saltin and other researchers have used the unique whole-body nature of cross-country skiing to study blood flow delivery. This approach has provided us great insight into the regulation of blood flow in both athletes and non-athletes.

Cross-country skiers demonstrate that cold weather is not an excuse to be sedentary, but rather an excuse to be great.

 

Ben Miller Benjamin 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.