Dreams and Erections

The average male has four to eight spontaneous erections every night while he sleeps. They usually occur during the REM stage, when dreaming is most common.

 In the case of the penis, there are actually two tasks that it handles:

	releasing urine from the bladder, known as urination
	releasing sperm and seminal fluid from the prostate gland, known as ejaculation
	Viagra helps with the second task: ejaculation.

When things are working properly, ejaculation is a three-step process:

	The man becomes sexually aroused.
	The penis responds by becoming erect.
	Stimulation of the penis causes ejaculation.

That sounds simple enough, but in many cases, step two does not happen, making step three difficult or impossible.

	A man takes a Viagra or Generic Viagra pill.
	The Sildenafil citrate enters his bloodstream and flows throughout his body.
	The Sildenafil citrate attaches to the PDE5 enzyme in his penis and disables most of it.
	When the man becomes sexually aroused, the brain sends the normal message to the NANC cells in his penis, which produce nitric oxide as usual.
	The nitric oxide creates cGMP, which starts relaxing the arteries in his penis.
	Since the PDE5 has been disabled, the cGMP in the penis does not break down. Instead, it builds up and lets the arteries in the penis fully dilate.
	His penis inflates with blood, and the man gets a full erection.