How Do Erections Work?


An erection seems like a simple thing, but it actually takes a complicated chain of events to make it happen.

Erectile dysfunction can be caused by many different physical and psychological factors, which break this important chain in different ways. That’s why there are different treatments required for ED, depending on the cause; the treatments must fix the particular link in the chain that is broken.

To understand the causes and treatment of your ED, you need to understand the chain of events the produce an erection.

The Erection Chain

This is a simplified version of the erection chain. There are many fine details that are important to doctors, but more than you need to know in order to understand the basic chain.

Erections begin in the brain. The brain receives stimuli, which might include sights, sounds, smells, touch, or even mental images. The stimuli produce a sense of arousal, which causes the brain to send nerve impulses to trigger a hormonal response.

  • Arousal may be prevented by psychological conditions such as stress, performance anxiety, or relationship problems.
  • The nerve impulses may be blocked by conditions that damage the nervous system, including multiple sclerosis (MS), Alzheimer’s disease, Parkinson’s disease, or surgery or radiation treatments.

The nerve impulses sent from the brain produce a chemical called nitrous oxide, which in turn produces another chemical called cyclic guanine monophosphate (cGMP). CGMP increases the size of the blood vessels that carry blood into the penis, and decreases the size of the blood vessels the carry blood away from the penis.

  • This link in the erectile chain can be broken by circulatory problems, which can prevent sufficient blood flow into the penis.  This is a very common cause of ED, especially in older men, or men in poor general health.
  • Some medical conditions may also interfere with the chemical signals and reactions that are necessary to direct the blood flow into the penis.

The increased blood flow into the penis inflates spongy tissues, called the corpora cavernosa, in the penis, which increase is size and become “hard,” much like a balloon when it is filled with air.

  • Physical damage or trauma to these tissues can prevent an erection.

The Role of Testosterone

It’s been known for some time that low levels of testosterone (the “male hormone”) can produce erectile dysfunction.  Part of this effect is due to a decrease of libido, or sexual desire; this can prevent the arousal that is the first link in the erection chain.

Recent studies indicate that low testosterone levels may also interfere with the chemical and enzyme reactions that regulate the blood flow into the penis.

Treating Erectile Dysfunction

Before choosing a treatment for ED, it’s important to understand the cause, and which link in the erectile chain are broken. For example, oral medications link Cialis and Viagra (which improve blood flow into the penis) won’t help if the nerves that carry impulses from the brain are damaged.

Also remember that ED may have more than one cause.  For example, you may have circulatory problems that make it difficult (but not impossible) to have an erection.  This might cause performance anxiety, which makes it impossible for you to maintain an erection.  In this cases, treating your erectile dysfunction will mean addressing both the circulatory problems and the psychological issues.

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