How Do Erections Work?

Erections occur when an individual with a penis becomes sexually aroused, but how exactly do they work? A combination of nerve signaling, blood flow, muscle control, and hormones contribute to functional erections.

With sexual arousal, the brain sends a signal through the spinal cord and nerves to the genital region. This signal triggers a hormonal response that tells the blood vessels in the genital region to dilate or become wider.

When the blood vessels in the genitals dilate, more blood is able to flow into the penis and fill the corpora cavernosa, which are the two spongey chambers that run the length of the penis. As the blood flows into the penis, the veins that bring blood away from the penis compress, effectively keeping the blood in the penis.

This process is what causes the penis to become firm and remain firm during an erection. However, once the individual reaches orgasm or ceases to be sexually aroused, the brain stops sending the signals that cause the hormonal response, and the penis returns to its flaccid state.

What causes erectile dysfunction?

Erectile dysfunction can occur when there is a problem with the nerve signaling process, when not enough blood flows into the penis, or when too much blood flows out of the penis. It can also be the result of damage to the erectile tissues, hormonal issues, psychological or emotional distress, or a side effect of taking certain medications.

Several medical conditions can cause nerve damage that impacts erectile function including diabetes, spinal cord injury, multiple sclerosis, and stroke. Blood flow to the penis can be negatively affected by diabetes, heart disease, high cholesterol, and high blood pressure. Erectile tissues can be damaged through trauma or by treatments such as radiation therapy or surgery for prostate or pelvic cancer. Lastly, two hormonal issues that can impact erections are low testosterone and thyroid disorders.

Given this long list of medical conditions that can affect erectile functioning, it makes sense that many health care providers think of erectile dysfunction as the first symptom of another medical problem. Therefore, it is very important to get regular checkups and talk to your health care provider if you develop erectile dysfunction. Remember, you are not alone, and fortunately, there are many treatment options available for erectile dysfunction, so you should not suffer in silence.


  • Najari, B.B., & Kashanian, J.A. (2016). Erectile dysfunction. Jama316(17), 1838-1838. DOI: doi:10.1001/jama.2016.12284

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