Impotence is the inability to attain or maintain an erection of the penis that is firm enough for sexual intercourse.

To initiate and maintain an erection, the penis must fill with blood. One type of blood vessels open wide to allow blood into the penis. Meanwhile, a second type of blood vessel squeezes down to keep the blood from leaving the penis. Nerve signals cause the proper changes in the blood vessels.

The following factors can cause erectile dysfunction:

Venous Leak

The blood vessels that keep the blood from leaving the penis may be injured or have disease. This can cause a leak in these vessels. Blood can escape through these leaks during an erection. This means that an erection cannot be made or may not last long.

Neurovascular Function

Problems with the nerves and blood vessels can cause impotence. Conditions that can cause problems include:

  • Nerve dysfunction—can reduce feeling in the penis, resulting in impotence
  • Diabetes —interferes with nerve signals
  • Hardening of the arteries —can cause reduced blood flow
  • Peripheral neuropathy, spinal cord injury, and surgery—can damage nerves
  • Side-effects from medications

Blood Vessels and Nerves of Male Pelvis
Nerves, blood vessels, penis
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Psychological Factors

Many of the nerve signals needed for an erection come from the brain. Emotional problems may play a role in men who suddenly develop impotence.