Skip to Content
Home > Patients & Visitors > Health Library > How Erections Occur
An erection occurs when your imagination or one or more of the senses
(vision, hearing, touch, smell, taste) are stimulated and you become aroused.
Your central nervous system sends nerve impulses that increase blood flow to
your penis. The blood fills the spongy chambers (corpora cavernosa) in the
penis, causing them to expand and become rigid. The veins that would normally
drain blood from the penis are constricted, trapping the blood inside and
maintaining the erection.
An erection goes down because the arteries narrow, the veins expand,
and the blood drains out of the penis. The penis returns to its normal size and
is no longer rigid.
See a picture of the
blood supply to the penis.
Four requirements for a normal erection are:
ByHealthwise StaffPrimary Medical ReviewerE. Gregory Thompson, MD - Internal MedicineAdam Husney, MD - Family MedicineSpecialist Medical ReviewerChristopher G. Wood, MD, FACS - Urology, Oncology
Current as ofMay 24, 2016
Current as of:
May 24, 2016
E. Gregory Thompson, MD - Internal Medicine & Adam Husney, MD - Family Medicine & Christopher G. Wood, MD, FACS - Urology, Oncology
To learn more about Healthwise, visit Healthwise.org.
© 1995-2016 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
Feeling under the weather?
Use our interactive symptom checker to evaluate your symptoms and determine appropriate action or treatment.
Our interactive Decision Points guide you through making key health decisions by combining medical information with your personal information.
You'll find Decision Points to help you answer questions about:
Get started learning more about your health!
Our Interactive Tools can help you make smart decisions for a healthier life. You'll find personal calculators and tools for health and fitness, lifestyle checkups, and pregnancy.
Send Us Your Feedback
North Kansas City Hospital