The line between fear and arousal is sometimes blurry, confusing, and difficult to perceive.

The Situation: You walk to the edge of a 25 story drop and look down.

The Reaction: A tingling sensation in your pelvic region.

The Questions: Why the hell is my junk tingling? Am I getting turned on?

The topic came up over at the Awkward Human Survival Group HQ and it turns out that both males and females have experienced this sensation. While it may affect many of us, there are others who will not have that reaction to heights, or feel the tingling in the same area.

Through research I’ve discovered that this feeling has everything to do with the nervous system. What many are experiencing is a fight or flight response.

Specifically, when we’re presented with a stressful or frightening situation the autonomic nervous system will switch modes. That system governs breathing, blood pressure, heart rate, pupils, arousal and a number of reflexes.

The autonomic nervous system (ANS) is comprised of two parts, the parasympathetic nervous system and the sympathetic nervous system. The parasympathetic mode is all about “rest and digest,” while the sympathetic system is the “fight or flight.” When you stare down that endless abyss from the roof of a 45 story building the ANS kicks into “fight or flight.” Here comes the adrenaline!

When you get that adrenaline hit, the sympathetic system is also engaged in transforming you into a lean, mean fighting machine. Your breathing and heart rate quicken. Digestion is put to a stop and the body releases its stores of blood sugars and fats for an energy boost. Blood vessels constrict all around the body, except for those supplying muscles which dilate for added strength.

In case of injury, our immune system drops everything on its to-do list and puts all hands at the ready for blood clotting. As we respond to the life-threatening situation, we may experience hearing loss and our pupils dilate to take in only the scene in front of us. Since our body is focused on protection, perhaps we should get those balls out of harm’s way as well?

The cremaster muscle is responsible for regulating temperature to the testes. Like a fine wine, sperm is to be served at the proper temperature, you know. The muscle will lower the scrotum in an effort to keep a temperature of 95° F.

If a man is in a colder environment, the cremaster moves the sack up to leach some body heat. If we’ve perceived danger, it’s thought that the sympathetic nervous system sends a message to the cremaster to draw the boys closer to the body to protect a man’s future generations.

Like experiencing hearing loss and tunnel vision during “fight or flight,” feeling the cremaster muscle on high alert is not something we’re accustom to and probably why that tingling sensation is so foreign to us. Everything that I’ve read so far on the topic of “fight or flight” has mentioned this below the belt activity, but none of the documents seem to site an expert, or source. I continued to dig around for a couple of days, but I get the impression that the testicles retreating at the first sign of fear is accepted as a fact. It makes sense.

If you’ve ever watched any of those nature programs, other male animals often engage in combat prior to mating to show the ladies that they are worthy mates. Obviously, if a moose is going to pick a fight to impress the females, he will want his junk as close to his body as possible. If he takes an antler to the balls, his mating days are over.

Explaining that tingling sensation for women is not as easy. Ladies do have a cremaster which is located at the point where the uterus and the uterine tubes meet, the round ligament. That ligament is responsible for supporting the uterus. When ladies are facing a steep drop into an abyss, could their bodies be securing the reproductive organs as well?

Complicating the explanation further, there’s a theory that women under stress have a less pronounced “fight or flight” mode. Many scientists now believe that females have a mode called tend and befriend. Dr. Shelley E. Taylor and her team poured through years of research and concluded that women are more likely to nurture offspring and seek out peers in stressful situations. Running away or fighting could possibly mean leaving an infant behind. Like the biological need of the male to protect his junk, the female also seeks to protect future generations. That’s accomplished by caring for the children and reaching out to others to form a stronger alliance.

Now, Taylor’s team doesn’t totally discount “fight or flight” in females. A sudden dangerous event may trigger “fight or flight,” but women begin to produce oxytocin the hormone associated with social bonding and care-giving. Thus, they become more cerebral and are able to look for solutions much quicker.

Meanwhile, Men produce testosterone and cortisol which are steroid hormones preparing them for battle. Therefore, I don’t feel comfortable concluding that the cremaster, or a muscle related to the pelvic floor will tingle if a female looks down at a terrifying drop. Obviously, there are women who have that sensation but I can’t speak to why it happens biologically.

Nevertheless, we can see that the autonomic nervous system (ANS) has a very important role for men and women. It is controlling our breathing, heart rate, digestion, blood vessels, energy levels and immune system, after all. This is what makes stress such a significant issue for our health. Don’t forget that the ANS also controls sexual arousal.

It’s easier to understand how some can associate pain with pleasure when you look at the functions of the the two branches of the ANS. Furthermore, I encourage you to look at this great article on Naomi Wolf’s book, Vagina: A New Biography by Maria Popova of brainpickings.org. In it, Popova talks about the link between mind and body, or vagina.

Put simply, a male dominated society where a woman can’t simply tweet her emotions on the internet without being harassed is probably a stressful environment. So, how could we expect a woman under stress all the time to be sexually aroused? For men, psychological impotence could be caused by an imbalance in the ANS as well. If he’s under constant stress and in “fight or flight” mode, erections are not going to happen.

I apologize that my investigation on that tingling sensation in your bathing suit area when you face scary heights resulted in a dour discussion of the complex realities surrounding sexual arousal. Hey, it’s all crotch centric! Cut me some slack, you’re stressing me out! Too late. My ANS has switched modes, I’m going to run before I end up like these moose.