​Erectile Process Complex  

The erectile process that produces a successful penis erection depends on a complex interaction of physical and psychological factors and relies on many physiological processes.

The most critical factor in the erectile process is blood flow to the penis; anything that disrupts blood supply disrupts erections, and poor blood flow is the cause of 70 per cent of physically caused erectile dysfunction.

A successful penis erection is dependent on an intricate chain reaction of messages between brain, nerve, blood and hormones, in particular:

  • Brain signals to nerves
  • Nerve signals to blood vessels
  • Hormonal interactions with both circulatory and nervous systems

An erection is the result of all of these physical systems working together, each doing its part at just the right time. Diabetic men are more prone to erectile dysfunction because of damage to nerve and blood systems.

Erectile Process Triggered By Sex Drive

Underlying this physical erectile process is the trigger of sexual desire.

Unless a man has a strong enough sex drive to set the erectile process in motion, many of the erectile treatments that deal with the physical aspects of getting an erection – like many erectile drugs – will not work.

Sexual desire can be affected by many things including

  • Emotional stress
  • Physical or psychological trauma
  • Low testosterone levels
  • Andropause (male menopause).

Most erectile dysfunction – defined as the inability to get or sustain an erection sufficient to complete intercourse – is physical in cause.  And the most common physical cause of disruption to the erectile process is reduced blood flow to the penis because of vascular problems.

How Erectile Process Develops

Penis erection occurs when stimulation – from either touch or visual cues – stimulates the brain and nerves to send messages to smooth muscles in the penis to relax, resulting in increased blood flow to the arteries in the penis.

How Stuff Works explains the process: nerve cells in the penis start producing nitric oxide, which leads to the creation of cyclic guanosine monophosphate (cGMP). These chemicals allow blood flow to inflate the penis like a balloon.

The testicles also release the hormone testosterone, which plays a role in determining when an erection happens and how firm it is.

If the arteries leading to the penis don't open up properly, the erectile process is disrupted and it's difficult or impossible for penis erection to occur. 

How Penis Changes in Erectile Process

When a man becomes sexually excited, the first change that occurs in the penis is the increasing of its length.

As the penis becomes erect there is an eight fold blood flow in, and pressure in the penis is at least twice the blood pressure in the main body. This is possible because the muscles of the pelvic floor contract around the base of the corpora cavernosa, the penile chambers containing the blood.

PDE 5 Inhibitors and Erectile Process

The brain has a mechanism for turning off the blood supply to the penis, an enzyme called a PDE 5 inhibitor.

The PDE 5 (phosphodiesterase type 5) enzyme breaks down the cGMP, effectively stopping it from continuing its action of relaxing the smooth muscle walls to allow arterial blood to flow in, so blood supply is reduced.
The body has 11 different types of these phosphodiesterase type enzymes, but only one – Type 5 – is found primarily in the penis. Once scientists discovered this fact, became relatively simple to create a drug to inhibit the production of PDE 5 and allow blood to continue flowing into the penis.

That’s why erection drugs like Viagra, Cialis and Levitra all work by inhibiting PDE 5 and are called PDE 5 inhibitor drugs.  And they all just work on once specific part of the erectile process – increasing blood supply to the penis by inhibiting the enzyme which stops blood supply.

Problems arise because these erection drugs sometimes also affect PDE 6, which is essential for good colour vision. Many men notice Viagra use gives the world a bluish tinge, and pilots are not allowed to take Viagra within six hours of flying.  

Natural amounts of PDE 5 inhibitors are found in some herbs used for erectile dysfunction treatment, including horny goat weed.

How the Erectile Process Is Completed

At orgasm, the signalling from the brain changes dramatically.
There is a sudden increase of noradrenaline production from nerves in the genitalia.
This neurotransmitter sent out from the brain to the genitals seems to both trigger orgasm and contract the muscle fibres in the corpora cavernosa and their supplying arteries.
As a result the blood flow into the penis reduces.
The pressure within the corpora drops, which relaxes the muscles shutting off the penile chambers and allows blood to flow out. The penis deflates to become flaccid again.