How does a man achieve an erection?

For a man to have an erection, a complex process takes place within his body.
 

• Erection involves the central nervous system, peripheral nervous system, hormones, psychological and stress-related factors, local problems with the erection bodies or penis itself as well as blood flow or circulation. The penile portion of the process leading to erections represents only a single component of a very complicated and complex process.  
  
  
• Erections occur in response to touch, smell, and visual stimuli that trigger pathways in the brain. Information travels from the brain to the nerve centers at the base of the spine, where primary nerve fibers connect to the penis and regulate blood flow during erection and afterward. 
  
  
• Sexual stimulation causes the release of chemicals from the nerve endings in the penis that trigger a series of events that ultimately cause muscle relaxation in the erection bodies of the penis. The smooth muscle in the erection bodies controls the flow of blood into the penis. When the smooth muscle relaxes, the blood flow dramatically increases causing the erection bodies to become full and rigid, resulting in an erection. Venous channels normally draining blood are compressed and close off as the erection bodies enlarge. 
  
  
• Detumescence (when the penis is no longer in a state of erection) results when muscle-relaxing chemicals are no longer released. Ejaculation causes the smooth muscle tissue of the erection bodies in the penis to regain muscle tone, which allows the blood drainage channels to open. As the extra blood drains from the erection bodies, the erection loses rigidity and the penis returns to its original flaccid state.   

ED occurs when this process does not progress normally. It’s a physical and mental activity, so it is important to remember that the sexual partner plays an integral role. If successful and effective management of erection problems and erectile dysfunction is to occur, discussions of treatment options should optimally include the couple.