The second phase of acute stress: the 'slow' response

The two phases of stress: fast and slow

The physiological response to acute stress generally involves two phases—the "fast" response in which adrenaline is released, and a second "slow" response in which cortisol is released. This technical resource reviews what happens in the body during each phase.

Why does the body have a stress response?

When encountering a stressful situation, the human body typically goes into what is known as "fight-or-flight" mode. Because it evolved as a survival mechanism, the biochemical response enables people and other mammals to react quickly to life-threatening situations. The carefully orchestrated yet near-instantaneous sequence of hormonal changes and physiological responses helps someone to fight the threat off or flee to safety.

Chronic stress affects nearly all parts of the body

Stress is our body’s internal mechanism to deal with changes in our internal balance. As such, the stress response affects nearly every organ system through a cascade of both fast and slow hormonal changes. While short-term stress can be adaptive, long-term stress may cause serious health issues.

Stress-induced adrenaline can trigger a 'hysterical strength' response

The stress response is a powerful ancient mechanism designed to maximize human survival—it can even result in superhuman strength. The adrenal glands are located just above the kidneys, and stress-induced adrenaline release causes more blood (and therefore more oxygen) to flow to your muscles, increasing performance.

Short-term cortisol spikes can boost the immune system

Elevated acute levels can enhance the immune system's ability to fight off infection or respond to injury. Chronic heightened cortisol levels, however, can lead to inflammation that harms cells and tissues over time.

Stress can be contagious—and scientists want to learn more about it

Researchers have shown that being around someone who is stressed can trigger a stress response in your body, such as elevated cortisol levels and elevated heart rate. One way this was recently studied was by having people watch stressful activities, like a recorded job interview or solving challenging math problems, and then sampling hormones in observers' spit.

Stress is a response to external triggers, while anxiety is persistent and internal

When distinguishing the two, stress is a reaction to identifiable situations like deadlines or conflicts, and its symptoms fade when the stressor is gone. However, anxiety may jump from one worry to another over time without any apparent cause.

The stages of fasting

What happens to the body when it goes without caloric intake? This article overviews the immediate physical effects of fasting. Within a day of going without food, the body will have used up its glucose stores and ordered the liver and muscles to convert their glycogen (glucose storage) into usable glucose. By the second day, glycogen stores will run out, forcing the body to use fat as energy. This process is known as ketosis.

The myth of sugar rushes vs. the reality of sugar crashes

It's generally accepted that sugar rushes are a myth, and that hyperactivity is a more psychological experience. However, there is real science behind the rare sugar crash that primarily impacts those with diabetes. Read this article to understand how historical and cultural factors have shaped sugar perceptions, and how low blood sugar can trigger shakiness, fatigue, weakness, and more in diabetes patients.

The body's response to cardiac arrest has been linked to near-death experiences

Most people who report near‑death experiences experience events like out‑of‑body sensations, altered cognition, emotional and spiritual shifts, or even supernatural phenomena, particularly during cardiac arrest. Research suggests many such experiences may be linked to brain-generated sensory distortions that can be experimentally replicated, suggesting a physiological rather than mystical cause.

Pollen and other allergens that are inhaled rarely cause anaphylaxis

Food allergies, insect stings, medications, and latex exposure are the main causes of the life-threatening allergic response called anaphylaxis. To reverse this severe reaction, a patient must typically receive an injection of epinephrine, otherwise known as adrenaline, a hormone that can relax some of the body’s muscles and increase heart rate, among other effects. Pollen allergies typically fuel a more localized reaction that isn’t as severe.

Touch deprivation can heighten anxiety and depression

Pacinian Corpuscles are pressure receptors just under the skin that send signals to the vagus nerve in the brain—that's the cranial nerve which regulates involuntary actions like breathing, heart rate, and the general "fight or flight" response. Activating those receptors can slow the heart, decrease blood pressure, and lead to the release of oxytocin and cortisol. The absence of touch, conversely, can promote negative feelings.

'FAST': An acronym to remember stroke symptoms to look for

The primary factor in surviving a stroke is how quickly one gets the appropriate medical treatment. “FAST” refers to the four most noticeable symptoms of a stroke: face-dropping ("F"), arm weakness ("A"), speech difficulty ("S"), and "time to call 911" ("T").

Blood pressure readings correspond to the peaks and valleys of heart beats

Pushing 2,000 gallons of blood through the body every day exerts a force known as blood pressure. Blood pressure is highest during the heart's contractile phase, known as systole, which forces blood through the circulatory system, and lowest during the heart's resting phase between beats, known as diastole.

The pancreas releases digestive enzymes and regulates blood sugar

The pancreas weighs about the same as a deck of cards and is smaller than the average adult human hand. This lopsided glandular organ controls blood sugar levels through insulin production and helps the body digest food by creating a neutralizing tonic filled with digestive enzymes.

What happens to your brain when you burn out?

You've probably heard of burnout, also known as the feeling of exhaustion that happens after a long period of being overwhelmed or stressed. It's often associated with work and careers, but other parts of life, like parenting, can cause burnout, too. Scientists are figuring out what happens, biochemically speaking, in the brain when burnout hits—and spoiler alert, it includes a neurotransmitter called glutamate. Watch this video to learn more.

Early peptide research focused on isolating the substances from animal tissue

In the first half of the 20th century, peptides including insulin and adrenocorticotropic hormone were isolated from animals to provide life-saving medicines. ACTH was isolated from the pituitary glands of cows and pigs and insulin was isolated from the pancreas of dogs and cows.

Can we speed up our metabolisms?

Listen to this 31-minute podcast to better understand what science knows and doesn't know about metabolism, as well as the only thing that seems capable of changing it. Scientists understand that the difference between a so-called “fast” and “slow” metabolism does not affect one’s ability to lose weight.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

What happens when we sleep

Sleep is a highly specialized and complex process that begins via signals from a region of the brain called the hypothalamus. As explained in this overview video from The Economist, the hypothalamus maintains our circadian rhythm by using light cues from our environment to regulate sleep via a compound known as melatonin. Once asleep, the brain begins the "sleep cycle" and progresses through the four stages of sleep over and over again each night.

Reduced inflammation from cold plunges lacks scientific support

The cold water triggers immediate cold shock, increasing heart rate and blood pressure, and prolonged exposure can lead to cold-water incapacitation and hypothermia. Plungers are encouraged to enter the water slowly and manage their breathing to reduce the risk of shock. Warm baths post-plunge are discouraged, and exercise is generally better for recovery.

'Slow productivity' as a humane approach to work

Work is increasingly encroaching on every part of our lives, while digital technologies enable supervisors to micromanage every part of an employee’s day. “Slow productivity” is a movement to alter the pace and quality of one’s work to avoid burnout and provide a more humane approach to work.

Schizophrenia symptoms, like psychosis, often first emerge among young adults

A combination of genetics, significant brain changes to the frontal cortex, and hormonal changes during young adulthood—late teens to early 30s—result in schizophrenic symptoms often showing up during this period. The stress of life changes at that age may also be a contributing factor.

Watch what the Ebola virus does inside the body in order to spread and survive

Once infected, the virus targets the body's immune cells, spreading the infection throughout the body. Patients exhibit severe flu-like symptoms. Ebola then targets the liver, which produces proteins that help blood clot, and the adrenal glands, which control blood pressure. The immune system may overreact to the viral invasion, releasing a cytokine storm that can result in shock, multiple organ failure, and death.

Opioids mimic naturally produced endorphins to dull pain

Once in the body, opioids bind to naturally occurring opioid receptors typically used by endorphins to temper pain. They trigger the release of dopamine, a desire-related hormone, and decrease noradrenaline, a neurotransmitter involved in heart and breathing rate regulation, meaning high doses can slow these processes to dangerous levels.

During the first Biosphere 2 mission, crew members lost 16% of their body weight

Food and oxygen shortages drove the “Biospherians” to split into two factions—one seeking to bring in outside resources and another aiming to maintain isolation for the experiment’s integrity. Psychological stress was exacerbated further by the increasing prevalence of insect pests.

In recent years a child anxiety expert has created and tested a novel phobia and anxiety treatment approach for children, focused on changing how parents respond to the fears.

Watch what the Ebola virus does inside our cells and organs in order to spread and survive.

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Scientists testing how climate change affects plants found, in a years-long simulation study, that poison ivy grew 70% faster with the resulting extra carbon dioxide.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Tattoos remain visible on your skin thanks to immune cells called macrophages

Telehealth demand for GLP-1s for weight loss is booming as consumers seek easier access.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

In 1984, Operation Smash Hit intentionally crashed a 239-ton train into a nuclear waste canister at 100 miles per hour to prove the canister's safety, which remained completely intact and lost just 0.29 of its 100 pounds of pressure.

Fast-casual restaurant Chili's is experiencing a resurgence, with its parent company recently reporting a nearly 32% increase in sales, thanks to passionate Gen Z fans on TikTok.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.

Use this calculator to find the dollar value of your mental load, from meal planning to coordinating after-school care for your children.

Brandi Chastain, the star of the 1999 US victory over China in the 1999 Women's World Cup, was a last-second choice to take the penalty kick that sealed the victory.

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

An initial public offering or 'IPO' is the process of a private company becoming public by putting shares of the company on the stock market for purchase.