What Does Adrenaline Do?

iStock/SomkiatFakmee
iStock/SomkiatFakmee

Reader Noah wrote in with a question—"Why does the human body need adrenaline?"

Adrenaline, or epinephrine, is a hormone and neurotransmitter produced by the adrenal glands that participates in the sympathetic nervous system's "fight-or-flight response" (or "acute stress response") to situations that are high-stress, dangerous and/or physically exhilarating. This release is an evolutionary adaptation that allows us to better cope with these situations.

Upon its release into the body, adrenaline binds to a variety of adrenergic receptors and causes several metabolic changes, like inhibition of insulin secretion and promotion of glucagon secretion by the pancreas, stimulation of glycogenolysis in the liver and muscles and stimulation of glycolysis in muscles. These changes and others together lead to increased blood glucose and fatty acids in the body and more energy production within the body's cells. The release of adrenaline further results in increased heart rate, contracted blood vessels and dilated air passages.

Ultimately, these changes allow more blood to get to the muscles and get more oxygen to the lungs quickly—so your physical performance improves and you're primed to either flee from danger or defend yourself.

10 Best U.S. Cities for Reducing Stress

Anaheim, California's Paradise Pier.
Anaheim, California's Paradise Pier.
Kirkikis/iStock via Getty Images

Looking to reduce your stress level? You might want to consider moving to Anaheim, California. Homeowner website House Method analyzed data from America’s largest 100 cities in order to determine the best—and worst—cities for managing your stress level.

The company looked at the same five factors across all 100 cities: commute time, mental health counselors per capita, the percentage of people who exercise regularly, walkability (specifically: to a park), and the number of yoga instructors and classes. Once all the data was tallied, Anaheim, California ended up in the top spot with an overall score of 38.5.

"The city has beautiful weather, lots of sunshine, and Disneyland. How could you be stressed when Mickey lives right down the road?," House Method’s senior editor and researcher David Cusick wrote of the results. "While Anaheim didn’t have the best score for commute time, it did rank number one for the city with the most mental health counselors per capita and has a very high percentage of people who like to exercise frequently."

California did well overall; four of the survey’s top 10 cities were located in The Golden State: Oakland came in second, Irvine came in fourth, and San Francisco came in fifth (despite its high housing costs). Seattle and Spokane, Washington—which came in eighth and tenth, respectively—tipped the scales in the west coast’s favor. Here are the 10 best cities for reducing stress:

  1. Anaheim, CA
  2. Oakland, CA
  3. Jersey City, NJ
  4. Irvine, CA
  5. San Francisco, CA
  6. Minneapolis, MN
  7. Madison, WI
  8. Seattle, WA
  9. Aurora, CO
  10. Spokane, WA

On the other end of the rankings were America’s worst cities for reducing stress, with Laredo, Texas taking the title as the very worst. “Laredo ranked last for the amount of mental health counselors per capita, percentage of people who exercise, and the amount of yoga instructors/classes,” Cusick wrote. “Filling out the bottom five cities are Bakersfield, California (96); Indianapolis, Indiana (97); San Antonio, Texas (98); and Jacksonville, Florida (99).”

For the full list of city rankings, visit House Method.

Human Body Temperatures Are Dropping, and Science Might Know Why

dcdp/iStock via Getty Images
dcdp/iStock via Getty Images

In 1868, German physician Carl Reinhold August Wunderlich started to popularize what’s become the most recognizable number in all of medicine: 98.6°F or 37°C, which is thought to be the normal average human body temperature. Though his methods later came under scrutiny—Wunderlich stuck an enormous thermometer under the armpits of patients for 20 minutes, a less-than-accurate technique—this baseline has helped physicians identify fevers as well as abnormally low body temperatures, along with corresponding illnesses or diseases.

More than 150 years later, 98.6° may no longer be the standard. Humans seem to be getting cooler. Researchers at Stanford University School of Medicine, in a paper published in the journal eLife, compared three large datasets from different time periods: American Civil War records, a national health survey from the 1970s, and a Stanford database from 2007-2017. By comparing recorded body temperatures, the researchers founds that men are now averaging a temperature .58°C less than what's long been considered normal, while women are .32°C lower. On average, each has decreased roughly .03°C every decade since the 1860s.

What drove us to chill out? Scientists have a few theories. A number of advances in human comfort have been ushered in since the 1800s, including better hygiene and readily available food, which may have slowed our metabolic rate (temperature is an indication of that rate). Chronic inflammation, which also raises body temperature, has decreased with the advent of vaccines, antibiotics, and better healthcare. The researchers propose that, on average, our bodies are healthier and slightly less warm.

After all, the average life expectancy in Wunderlich’s era was just 38 years.

[h/t The Independent]

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