Home > Health & Wellness > 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 MedicineSpecialist Medical ReviewerChristopher G. Wood, MD, FACS - Urology, Oncology
Current as ofMay 22, 2015
Current as of:
May 22, 2015
E. Gregory Thompson, MD - Internal Medicine & Christopher G. Wood, MD, FACS - Urology, Oncology
To learn more about Healthwise, visit Healthwise.org.
© 1995-2015 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
Use our interactive symptom checker to evaluate your symptoms and determine appropriate action or treatment.
I want to...
1111 Duff Avenue Ames, Iowa 50010
515-239-2011 Email us
Anywhere in Iowa 800-524-6877