TWIN FALLS — Victoria Miksis' brain recently experienced a massive chemical event.
The rubber-band bounce of the Perrine Bridge under her feet. The gasp of pushing her toes over the platform's edge. The terror of falling. The euphoria of the parachute opening.
In less than 120 seconds, a dump of epinephrine, norepinephrine and cortisol. A blissful finish of dopamine and endorphins that could last days.
What happens in the brain when a person BASE jumps depends on several factors said Dr. Mason Robison, a Twin Falls psychiatrist.
But a first-timer like Miksis, a 17-year-old from Healdsburg, Calif., would have an intense experience, said Sean Chuma, a Twin Falls professional BASE jumper and instructor.
Chuma, who has 1,970 jumps notched on his belt, said the feeling changes the more you jump, but you never forget your first time. Before he strapped himself to Miksis and the two went off the bridge, Chuma knew intimately what was about to happen in both their brains.
For much of the morning in late June, Miksis said, she was not anxious about jumping surrounded by family. But when she hiked her leg over the rail, she became immediately nervous.
"I was like, 'Oh my gosh, please don't fall, please don't fall. Please platform don't break, don't break.' "
The stress of preparing to jump doesn't feel like work stress or dread, Chuma said. It's anticipatory stress. The jumper is still in control and could run from the situation.
"It's not go time yet. It's awkward, but they are not about to fall or anything," said Chuma, who has operated tandembase.com for three years.
At this point, Miksis' brain initiates the fight-or-flight response humans have developed to survive threats, said Dr. Cheri Wiggins, a physiatrist at St. Luke's Clinic for neurology and physiatry, which diagnoses and treats disorders causing temporary or permanent impairment.
The amygdala - the brain's sensory center for risk and danger - triggers the hypothalamus, which signals the pituitary gland to release a blend of three stress hormones from Miksis' adrenal glands to help her survive the jump.
As the epinephrine, norepinephrine and cortisol take effect, Miksis' heart rate and blood pressure rise, pupils dilate and her mucus dries.
"It basically shuts down everything that's not essential so that all of your resources can go toward survival," said Wiggins, whose husband is a BASE jumping instructor. "Your pupils dilate so you can see everything. Your heart rate and blood pressure go up so you are primed for action."
As Chuma and Miksis position themselves on the platform, Miksis must put her toes over the edge. With nothing but 486 feet of air below, it's the "step bad dreams are made of," Chuma said.
Miksis' anxiety and stress turn into a sharp fear as she realizes "this is real."
This change could be a rush of epinephrine, commonly called adrenaline. But Wiggins said it's more likely the building of all three stress hormones in Miksis and the feeling of being exposed to them longer and longer.
"They all kind of kick in at the same time, so it might just be that it got scarier at that time," Wiggins said. "That cascade has already started."
While the three hormones are important in the body's response, Miksis also has conscious thoughts about the danger as she peers over the edge. Her emotions about the situation also affect her body, Wiggins said.
Chuma said many tandem jumpers lean back into him, as they feel they're not in control. There's nowhere to run. Human instinct is to get off the ledge.
"I think that is the strongest part of the jump, when there is a lot going on in their brain because they have to go against their instinct of self-preservation," Chuma said.
As the two leaned over the edge and gravity took hold, Miksis tried to scream. She said her heart leaped into her throat.
"I let out this scream thing, but it was silent because I tried to scream so loud I couldn't scream at all," she said. "I think my heart was blocking my voice or something."
Immediately after she stopped trying to scream, Miksis said, she was overwhelmed by bliss.
"It was smooth, fluid and relaxing."
This feeling is caused by a massive pulse of dopamine, a neurotransmitter associated with the brain's reward center, Robison said. Much of a person's life is spent seeking more dopamine, from drinking coffee and smoking cigarettes to risky behaviors such as fighting or doing drugs, she said.
Although the threat is gone and Miksis is flooded with joy caused by dopamine, the fear manufactured by the amygdala is still present. Dopamine simply overpowers the brain, Robison said.
"People always call us adrenaline junkies, but I don't really think of it that way," Chuma said. "The part I'm looking for is how much fun it is. I have heard people say that it is a misconception, that it is a dopamine rush that I'm looking for. That's the one that makes you feel like you just had a lot of fun."
Dopamine release can happen in nanoseconds and can produce endorphins. A release of endorphins can occur during intense aerobic exercise, but it also can happen during brief, dangerous activities, Wiggins said.
"It is kind of a natural opiate," she said.
As Chuma and Miksis floated to the ground, the first-timer said, her feeling of bliss slowly tapered and transitioned into a focus she described as "tunnel vision."
Chuma said that's not the bliss wearing off, but rather the brain snapping to attention and realizing the threat of landing. Wiggins said the intense focus Miksis described as she landed is caused as the three stress hormones produced earlier are put to work.
"It is part of that fight-or-flight response and being able to focus on the most important thing," Wiggins said.