How does my body react to stress response?

Patricia A. Bloom, MD
Geriatric Medicine
Our brain is hard-wired to be on the lookout for threat. When threat, or stress, is perceived, a “stress reaction” is immediately initiated, involving multiple areas of the brain and many systems in the body. The “fight or flight” response, resulting from activation of the sympathetic nervous system, kicks into action, and blood pressure increases, heart rate speeds up, breathing becomes rapid and shallow, all in the interest of quickly delivering nutrients to muscles so that they can contract, enabling us to fight or run. There is an outpouring of stress hormones and neurotransmitters, and the immune system goes into overdrive, releasing inflammatory chemicals to help ward off invaders like bacteria or viruses. All of these automatic reactions can be very useful in the face of acute threat, but when activated frequently overtime, they can cause or promote many different psychological and physical problems.
Dr. Kathleen Hall
Preventive Medicine
When we are stressed, we release excitatory neurotransmitters. Your body responds to these hormones by increasing your heart rate, blood pressure, and respiration. More blood is pumped into your muscles, sending more oxygen to your muscles, brain, heart and lungs. Blood flow may increase 300 percent to 400 percent, preparing your lungs, muscles, and brain for added demands. The amount of sugar of glucose increases in your blood, which accelerates your metabolism so you can take immediate action in an emergency. Your blood thickens as platelets prepare to stop bleeding quickly. As the blood thickens, oxygen increases in red cells and promotes better function of the white cells that prevent infections. The spleen discharges red and white blood cells, allowing the blood to transport more oxygen.
John Preston, PsyD
How does the body generally respond to stress?

All biological processes are fundamentally adaptive. They have developed over hundreds of thousands of years in the direction of greater ability to adapt and survive. The following information is about normal stress reactions (not anxiety disorders).  There are 4 common stress responses hard-wired into the human brain and body: fight, flight, freeze, and tend and befriend. The first three are discussed below. Tend and befriend is a response to danger seen in most mammals including humans (especially in females) where if there is danger, the parent, rather than running away, will put their life on the line to protect their offspring.

Now on to the 3 Fs. Freeze responses are seen when facing life-threatening, no-escape situations; people can faint. This is what some call playing opossum.  Another form of freeze is fainting right after exposure to a stressor. Finally there is the well-known reaction when seeing blood or giving a blood sample. Dizziness, light-headedness and fainting may occur.

Flight and fright responses typically include: rapid heartbeat, increased blood pressure, and sweating, trembling, increased glucose in the blood stream, shortness of breath, dizziness, chills or hot flushes. In flight hands and feet become cold; in fight, they become hot.

All of these immediate changes are considered to be normal responses, designed by nature to enable a person to take sudden action to either run away from/escape a stressful situation, of fight to protect oneself.
Anxiety disorders have the same symptoms but they occur:
  1. Out of the blue (not provoked by an immediate stressor),
  2. With an intensity of response that appears to be excessive,
  3. Anxiety can be almost continuous, throughout the day; and/or,
  4. The anxiety results in impairment, an effect on a person where they cannot function optimally in school, work, or interpersonal relations due to the anxiety.
Michael T. Murray, ND
Naturopathic Medicine
The stress response is as follows:
  • The heart rate and force of contraction of the heart increase to provide blood to areas necessary for response to the stressor.
  • Blood is shunted away from the skin and internal organs except the heart and lungs, while the amount of blood supplying required oxygen and glucose to the muscles and brain is increased.
  • The rate of breathing rises to supply necessary oxygen to the heart, brain, and exercising muscle.
  • Sweat production increases to eliminate toxic compounds produced by the body, and to lower body temperature.
  • Production of digestive secretions is severely reduced because digestive activity is not critical to counteracting stress.
  • Blood sugar levels are raised dramatically as the liver dumps stored glucose into the bloodstream.
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If your stress response gets kicked up, a whole SWAT team of stress hormones kicks in to ready your body systems for action. Here’s the 1–2–3 of what happens when a crisis hits:

  • The region of the brain called the hypothalamus releases a stress coordinator called corticotropin-releasing hormone (CRH).
  • CRH rushes over to the pituitary, a pea-sized gland at the base of the brain, and tells it to release adrenocorticotropic hormone (ACTH) into the bloodstream.
  • Fast-talking ACTH tells the adrenals (yep, they’re called into action again) to release a major stress hormone, cortisol.

This sequence of events is known in scientific circles as the hypothalamicpituitary- adrenal axis, or HPA axis. It is your body’s main stress-response system. Think of it as old-fashioned messengering in a kingdom in the midst of war – a way of getting the word out to the body that it’s time to mobilize the troops and prepare for battle.

From The Mind-Beauty Connection: 9 Days to Less Stress, Gorgeous Skin, and a Whole New You by Amy Wechsler.

Ms. Ashley Koff, RD
Nutrition & Dietetics
From an evolutionary and survivalist perspective, stress is a good thing. It's supposed to prime the body for battle and get us out of harm's way. The problem, though, is that our physical reaction is the same every time we sense a potential threat, whether it's real and coming from something truly life-threatening, or just the To Do list and screaming kids.

First, the brain signals to the adrenal glands to release epinephrine, better known as adrenaline. This is what causes your heart to pick up speed as blood rushes to your muscles in case you need to make a run for it. That adrenaline, by the way, steals blood from the skin and face to allocate it toward your muscles, which is why you can suddenly look pale as a ghost or become white with fear. As soon as the threat passes, your body returns to normal. If the threat doesn't pass and your stress response gets stronger, then a whole wave of stress hormones gets released in a series of events along the hypothalamic-pituitary-adrenal (HPA) axis. The hypothalamus, a region of the brain, first releases a stress coordinator called corticotropin-releasing hormone (CRH). The hypothalamus is frequently referred to as the seat of our emotions. It's our chief leader in emotional processing. The split second you feel anxious, deeply worried, scared, or simply concerned that you can't pay a bill, the hypothalamus secretes CRH to start a domino effect ending in cortisol (the body's chief stress hormone, aiding in that famous fight-or-flight response) rushing into your bloodstream.
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When you feel threatened, your body automatically triggers what is called the fight-or-flight response. If you were a caveman hunting for food in prehistoric times and a saber-toothed tiger came into your path, your body would prepare to fight the tiger or to flee from it.

Fortunately, you won’t run into a saber-toothed tiger these days. But your body responds to almost every stressful moment in your life with the same response, as if you were encountering lots of tigers every day. For example, a bad grade on a test, a breakup with a girlfriend or boyfriend, being followed on the street, or being startled by a noise when you’re home alone can all cause your body to respond immediately with the fight-or-flight response.

Different people feel stress in different parts of their bodies. For example, you might find it harder to breathe, and your friend might feel really warm. Your reaction may also change at different points in time. One stressful situation might give you a stomachache, and another might make your shoulders tense. No matter what your physical signs, be aware that your body is letting you know that it is stressed and wants to return to a relaxed state.

Here is a list of physical symptoms that can be caused by stress. Some of these may last a few minutes or come and go, while others may last for days or even longer.

  • asthma
  • stomachache
  • nausea
  • heartburn
  • muscle tightness
  • sweating
  • trembling
  • headache
  • change in appetite
  • unusually rapid speech
  • change in weight
  • change in sleep habits
  • change in skin: dryness, itchiness, rash
  • chest pains
  • dizziness
  • throat feels like it is closing
  • shortness of breath or shallow breathing
  • heavy or faster breathing
  • racing or pounding heart
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Your body responds to the heightened sympathetic and adrenal gland activity in the following ways:

  • Your heart rate increases. This allows your heart to pump more blood to your muscles and organs, thereby bringing in fresh supplies of oxygen and glucose.
  • Your breathing quickens to increase the amount of oxygen your lungs absorb.
  • Your blood pressure elevates to make sure all of the organs in your body, including your brain, are infused with vital nutrients such as oxygen and glucose.
  • Blood flow diverts from your gut to your skeletal muscles, preparing you for "fight or flight." The performance of your muscles is critical in the stress response because your muscles determine how fast you can run and how hard you can fight.
  • Blood flow shifts in the brain away from the higher cerebral cortex to the lower, more primitive areas. This allows for heightened sensory perception and quicker reaction times, but the shift in blood flow reduces your ability to solve complex problems.
  • Your libido decreases. Nature has decided that when there is a life threatening event, it is not a good time to reproduce.
  • Your digestion turns off. Your gut largely shuts down during the stress response because your body has more important things to do. Your body's focus is on keeping you alive; it can process what you ate for lunch later.
  • The muscles around your lower back, neck, and jaw tighten. You can't have a floppy spine or jaw if you want to run fast or fight well.
  • Your blood sugar increases. This is important because your muscles and brain need more fuel.
  • Fats are released into your bloodstream. Both fats and sugars can be used as fuel for your muscles as you fight or run away from danger, although sugar is the preferred fuel.
  • Circulating platelets in your blood activate so that if you get cut during the fight-or-flight response the bleeding will stop more readily.
  • You sweat, to help your body cool down quickly.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.