You’ve been getting erections since puberty, but have you ever stopped to think about the reason why? Understanding the physiological process of getting an erection can help you look at ED in a whole new light.

What Makes a Penis Erect?

Your penis has two chambers inside it called the corpora cavernosa. These chambers extend from the head of your penis deep into the pelvis. The insides of these chambers are made of spongy tissue and have the ability to gain blood volume and grow in size.

When you’re at work, hitting the gym, or running errands, the arteries supplying blood to your penis are only partially open. This provides the blood flow needed to keep your tissue healthy.

The magic happens when you become aroused. In response to physical or mental stimulation, your brain sends signals to trigger a hormonal response that allows those same arteries to open completely.

Open arteries allow more blood to enter the corpora cavernosa. The blood enters faster than it can leave through the veins. The veins get compressed, trapping blood in your penis. This chain reaction lets you achieve and maintain an erection.

When your brain stops sending signals that indicate sexual arousal, the hormonal response ends. Your arteries go back to their normal state and your penis returns to a flaccid state.

How Erection Occurs Step 1                       How Erection Occurs Step 2                  step3

How Erectile Dysfunction Occurs

Erectile dysfunction means something is standing in the way of your body’s natural process of getting and sustaining an erection. Usually, this is one of three things:

  1. Your brain isn’t sending the right signals to your penis. Neurological disorders such as multiple sclerosis (MS), Alzheimer’s disease, and Parkinson’s disease can lead to ED by disrupting your brain’s ability to signal sexual arousal to your reproductive system.
  2. The blood flow to your penis is inadequate. High blood pressure, heart disease, and high cholesterol can all affect blood flow to the penis, making erections difficult to achieve.
  3. Your erectile tissue is damaged. This can happen when a man suffers from Peyronie’s disease or has undergone radiation treatment for prostate cancer.

Treating ED

ED is more common than you might think, affecting half of guys over the age of 40 (1). If you’re like the vast majority of guys, it’s not something that’s easy to talk about, but you’re definitely not alone in your struggle.

The first step in treating ED is identifying the cause of your difficulty getting or keeping an erection. Once a cause has been identified, you can get the help you need. Review our ED Treatments page to learn more about treatment options such as lifestyle changes, medication or a penile implant.


  1. NHS Choices
Erectile Dysfunction treatment options »