HOW STUFF WORKS
QUIZZES

FOLLOW US
The Ultimate Viagra Quiz
by Staff
Lots of rumors go around about Viagra, but what does this medicine actually do inside the body? Take the Viagra Quiz to see what you know about that little blue pill.

How does a penis become erect?

  • muscle contractions
  • pressurized blood
  • rapid semen buildup

How does the blood flow to the penis change during an erection?

  • During an erection, a man's heart is beating faster, so more bloods flows to all parts of his body, including his penis.
  • During an erection, the arteries bringing blood to the penis open wider, and the veins that take blood away tighten up.
  • During an erection, the brain floods the body with hormones, which increase blood flow to the arteries in a man's penis. As his sexual arousal intensifies, so does the blood flow.

The first drug developed to treat erectile dysfunction was called phentolamine. How was it originally demonstrated?

  • A group of urologists at a medical convention in Vegas were treated to the groundbreaking on-stage erection of one of their esteemed colleagues.
  • Volunteers were sought amongst male strippers to demonstrate the drug during closed-door trials in front of key stakeholders and regulators.
  • Elderly gentleman with high stakes in the matter offered to be studied and documented by a team of urologists looking to cure erectile dysfunction.

What were the down sides of phentolamine that lead to further research in treating erectile dysfunction and the development of Viagra?

  • Phentolamine causes an instant and uncontrolled erection -- not always the most sure-fire way to impress the ladies, and a little awkward if something besides love-making suddenly comes up.
  • Phentolamine has to be delivered via an injection because it affects a common type of muscle tissue -- smooth muscle -- that's not unique to the penis in particular. As a pill, it could cause problems for smooth tissue in other parts of the body like the intestines and blood vessels.
  • both

Let's get back to the arteries and veins in the penis. Under normal circumstances, how do they know when to expand and contract?

  • Physical stimulation alerts the sensitive blood vessels it's their time to shine.
  • The brain sends signals to stimulate the production of a certain type of enzyme. These enzymes in turn produce a chemical that causes the smooth muscle inside the arteries to relax -- letting blood pump into the penis.
  • The brain signals the arteries with a burst of testosterone and the veins with a relaxing dose of estrogen, causing the former to expand and the latter to contract.

So what happens during erectile dysfunction?

  • When a man experiences erectile dysfunction, it's usually because the nerve signals triggering the release of nitric oxide get lost on their way from his brain to his penis.
  • Erectile dysfunction is most often caused by factors like stress, fatigue and side effects from alcohol and other medication.
  • Erectile dysfunction is most commonly caused by a lack of dilation in the arteries because there's not enough cGMP.

How does Viagra work to treat this problem?

  • Viagra disables another enzyme -- phosphodiesterase or PDE -- which completes the cycle by decomposing cGMP back into its original chemical state. Take away the PDE and sufficient cGMP can build up for an erection.
  • Viagra augments the levels of nitric oxide in the penis so more cGMP can be produced.
  • Viagra contains supplemental amounts of cGMP, giving the arteries the boost they need to flow freely.

There's PDE in other areas of the body too -- how does Viagra get around that?

  • Viagra developers found that one specific kind of PDE (PDE5) out of the body's 11 types, is found primarily in the penis. This enabled them to target one specific area without interfering with other parts of the body.
  • Viagra researchers were pleased to find out that while there are other types of PDE, Viagra does not severely disrupt their functioning in any significant manner because they perform tasks unrelated to cGMP.
  • neither

How does Viagra temporarily take out PDE5?

  • Viagra decomposes the PDE5 back into generic PDE for a period of time long enough for a man to get an erection.
  • Viagra diverts PDE5 to other parts of the body so it doesn't interfere with the process of forming an erection.
  • Viagra contains a chemical that attaches to the receptors that would normally be locking onto cGMP, thereby preventing the PDE5 from gobbling it up.

It's not all blue skies after that -- what's arguably the weirdest side effect that can come from popping back a few Viagra?

  • You may get a little more than you bargained for -- in the form of an erection that just won't go away.
  • Some Viagra users said they temporarily lost their vision in one or both eyes -- or had their vision become tinted blue.
  • A sudden decrease or loss of hearing has been reported among some men who took Viagra.