How to Show an Adrenaline Rush

Had an adrenaline rush when two rhinos ran across our path about three yards ahead. These were not those rhinos, we had no time for photos then. These rhinos were nice and calm.
​Photo from South Africa in 2011, taken by Kate Ota.

I earned a Masters in Molecular, Cellular and Integrative Physiology, and the part that I’ve used the most is the integrative aspect. Classes taught me not just what one signaling chemical does, but how it impacts others. Some of my favorite things I learned were why alcohol makes you urinate way more than any other beverage, why nicotine is so addictive, and how epinephrine (aka adrenaline) impacts your entire body.

I thought it would useful to discuss how adrenaline impacts the body, because any good story is going to have a scene where your character feels that shot of adrenaline—whether it’s from fear, excitement, or a combination of both. The section called “how your character will feel” discusses how to show the impact of adrenaline for each part of the body.
 
Adrenaline is produced in the adrenal gland, which sits on top of each kidney like a party hat. It’s a hormone, so it travels through the blood. Therefore, it has access to and impacts most of the body. It prepares you for sudden physical exertion as a reaction to a stressor, like a bear or an important exam.

Let’s break this down by body part:
 
Blood vessels/muscles
What happens: Some vessels will dilate (widen) and allow more blood to flow through them. Some will constrict. It all depends on location, location, location. Skeletal muscles, the ones you have conscious control over like those in the legs and arms, have lots of blood vessels in them. These blood vessels will dilate to deliver more oxygen to the skeletal muscle. Afterall, you need those muscles to run or fight. However, adrenaline decreases the activity of smooth muscle, which you don’t have conscious control over, like what lines your intestines, for example. You don’t need active intestines to fight or run. Vessels delivering blood to the digestive system, urinary system, and reproductive system will constrict, allowing blood to be sent where it’s most useful for survival.

But why do people sh*t their pants or urinate when they’re scared? So glad you asked. It’s because the smooth muscles at the end of your large intestines and in the bladder also relax, and if there was something in the rectum waiting to be released at an appropriate time or a lot of pressure within the bladder that was being held, well. You didn’t need that extra weight slowing you down anyway.

How your character will feel: They will have warm, reactive muscles, which will be able to produce more power than usual. If they were hungry/turned on/in need of a bathroom before, this will no longer be a major concern. There’s a reason why most fight scenes don’t include the inner monologue wondering about lunch or the bathroom—those systems are suppressed.
 
 
Heart
What happens: It beats faster and harder. This will increase blood pressure. Pretty straight forward.

How your character will feel: pounding heart, maybe feeling the heartbeat in their head, even a headache if the stress is chronic.
 

Skin
What happens: Welcome to Sweatytown, USA. Now that those blood vessels around muscles are dilated, there’s more blood going through muscular areas. That blood will lose heat through the skin when it passes near the surface, so the skin is generally warm over big muscles. The muscles themselves are also producing more heat as they’re used. But remember, the body can shunt blood away from things less necessary to fighting/flighting, so some people also experience very cold hands. (Who needs fingers to run? Apparently not you.) Also common: pale (as in bloodless) faces, which flush again later after physical activity or embarrassment.

How your character will feel: Sweaty palms and armpits are most common for emotional stressors like running into a crush or a big test. For physical stress, like seeing a bear and realizing you need to run (not the recommended method of bear safety), they may get more of an all-over body sweat.
 

Lungs
What happens: Faster breathing. Get that oxygen to those muscles! Some people will take short shallow breaths, but that’s not going to get enough oxygen in there, and these individuals may pass out instead. Adrenaline also relaxes the smooth muscle in the lungs, which opens the airways wider in the hopes of increasing oxygen.

How your character will feel: While most characters will breathe faster, and take deeper breaths, reactions may vary. Anxiety (a chronic stressor) may cause a sense of chest constriction, but the best reaction to that is deep breaths. The character may also breathe faster and shallower, but remember this can cause light headedness, dizziness, and/or fainting.
 

Liver
What happens: Adrenaline releases glucose (sugar) from where it’s stored in the liver as glycogen. After all, muscles need the energy in sugar to contract, and the body is anticipating using the muscles a lot. If this ends up being a false alarm situation, like a scare in which there is no actual fighting/flighting needed, the blood sugar may take a while to go back down. This may lead to a lack of hunger for a time afterwards—it varies by person.

How your character will feel: There will be a spike in blood sugar. Most characters won’t notice this, but diabetic characters might be strongly affected.
 

Eyes
What happens: The pupils dilate to allow more light in. More light = more information. Ever seen a cat about to pounce? Its pupils get huge just before the motion, so they can get more information about their prey.

How your character will feel: Tricky, since this is something most people won’t actually feel themselves. But your character may see it in others. It can be shown subtly. For example, if it’s dark, perhaps your character was struggling to see before, but after hearing that wolf howl, they’re able to navigate the dark forest much more easily.
 

Anaphylaxis
What happens: Anaphylactic shock is when the body’s reaction to something is so bad, the heart is no longer able to pump, and blood vessels are too constricted. The heart and circulation sections above explain how the adrenaline counteracts that exactly. But remember, it has a short lifespan in the body compared to other hormones, so anyone who experiences anaphylaxis needs medical attention ASAP.

How your character will feel: A character in anaphylaxis will have trouble breathing, even chest pain, and may lose consciousness. The EpiPen is injected and they will feel all the effects of adrenaline, but most notably, their heart will pick up the pace.
 

Overall
Because the body is now ready to fight or run away at the drop of a hat, the character may experience any of the following: jumpiness, jitteriness, trembling (especially hands), ignoring physical pain in order to focus on an immediate physical task, or palpitations (fluttery/irregular heartbeat).

Chronic stressors can cause the release of another hormone, cortisol. And that’s usually associated with more chronic effects, like stress-induced weight loss.
 
​
Hopefully this list gave you some methods of showing your character’s feeling of excitement, nervousness, fear, or surprise. Did any others come to mind? Does it help to know the physiology behind the feeling? Let’s discuss in the comments!