As blood flows into the penis, the corpora cavernosa swell, and this swelling compresses the veins (blood vessels that drain the blood out of the penis) against the tunica albuginea. Compression of the veins prevents blood from leaving the penis. This creates a hard erection. When the amount of cGMP decreases by the action of a chemical called phosphodiesterase type 5 (PDE5), the muscles in the penis tighten, and the blood flow into the penis decreases. With less blood coming into the penis, the veins are not compressed, allowing blood to drain out of the penis, and the erection goes down.
Having learned a great deal more about erectile dysfunction including its risk factors and causes, you should be equipped to assess your own erectile function. If you have experienced erectile issues or you have some of the risk factors mentioned above, it may be worth making a trip to your doctor’s office. If you choose to seek help, give your doctor as much information as you can about your symptoms including their frequency and severity as well as the onset. With your doctor’s help, you can determine the best course of treatment to restore sexual function.
Erections are neurovascular events, meaning that nerves and blood vessels (arteries and veins) are involved in the process of an erection and all must work properly to develop a hard erection that lasts long enough. Erection begins with sexual stimulation. Sexual stimulation can be tactile (for example, by a partner touching the penis or by masturbation) or mental (for example, by having sexual fantasies, viewing porn). Sexual stimulation or sexual arousal causes the nerves going to the penis to release a chemical, nitric oxide. Nitric oxide increases the production of another chemical, cyclic GMP (cGMP), in the muscle of the corpora cavernosa. The cGMP causes the muscles of the corpora cavernosa to relax, and this allows more blood to flow into the penis. The incoming blood fills the corpora cavernosa, making the penis expand.
Vacuum devices for ED, also called pumps, offer an alternative to medication. The penis is placed inside a cylinder. A pump draws air out of the cylinder, creating a partial vacuum around the penis. This causes it to fill with blood, leading to an erection. An elastic band worn around the base of the penis maintains the erection during intercourse.
When stimulated by the nerves, the spongy tissue arranges itself in such a way that more blood can be stored in the penis. The veins running through the outer sheath of the penis then compress which stops the blood from leaving the penis. As the blood is stopped from flowing out, the penis fills with blood and stretches within the outer casing, giving an erection.
Several pathways have been described to explain how information travels from the hypothalamus to the sacral autonomic centers. One pathway travels from the dorsomedial hypothalamus through the dorsal and central gray matter, descends to the locus ceruleus, and projects ventrally in the mesencephalic reticular formation. Input from the brain is conveyed through the dorsal spinal columns to the thoracolumbar and sacral autonomic nuclei.
Damage to the autonomic pathways innervating the penis may eliminate "psychogenic" erection initiated by the central nervous system. Lesions of the somatic nervous pathways may impair reflexogenic erections and may interrupt tactile sensation needed to maintain psychogenic erections. Spinal cord lesions may produce varying degrees of erectile failure depending on the location and completeness of the lesions. Not only do traumatic lesions affect erectile ability, but disorders leading to peripheral neuropathy may impair neuronal innervation of the penis or of the sensory afferents. The endocrine system itself, particularly the production of androgens, appears to play a role in regulating sexual interest, and may also play a role in erectile function.
The inability to achieve or sustain a sufficiently firm penile erection (tumescence) to allow normal vaginal sexual intercourse. The great majority of cases are not caused by organic disease and most men experience occasional periods of impotence. It is often related to anxiety about performance and is usually readily corrected by simple counselling methods which prescribe sensual massage but forbid coitus. Organic impotence may be caused by DIABETES, MULTIPLE SCLEROSIS, spinal cord disorders and heart disease. Many cases can be helped by the drug SILDENAFIL (Viagra).
Erections are more complicated than you think. Your brain, nerves, heart, blood vessels, and a whole lot of hormones have to work together perfectly or nothing happens. It’s a lot to ask, and sometimes things break down. And while ED happens to most guys at some point in their lives, erectile dysfunction isn’t something you can just ignore and hope it goes away.
Davis Liu, MD is a board certified family physician, patient advocate, physician leader, blogger, and the author of two books, including The Thrifty Patient – Vital Insider Tips for Saving Money and Staying Healthy. He’s passionate about making healthcare more convenient, personalized, and affordable. Prior to joining, Dr. Liu was a practicing primary-care doctor for fifteen years at Kaiser Permanente in Roseville, California. He also served on the Permanente Medical Group (TPMG) Board of Directors as Vice Chair of the Finance and Audit committee and the Governance committee. Dr. Liu graduated summa cum laude and Phi Beta Kappa from the Wharton School of Business at the University of Pennsylvania. He received his medical degree from the University of Connecticut School of Medicine.
Psychosocial factors are important in all forms of erectile dysfunction. Careful attention to these issues and attempts to relieve sexual anxieties should be a part of the therapeutic intervention for all patients with erectile dysfunction. Psychotherapy and/or behavioral therapy alone may be helpful for some patients in whom no organic cause of erectile dysfunction is detected. Patients who refuse medical and surgical interventions also may be helped by such counseling. After appropriate evaluation to detect and treat coexistent problems such as issues related to the loss of a partner, dysfunctional relationships, psychotic disorders, or alcohol and drug abuse, psychological treatment focuses on decreasing performance anxiety and distractions and on increasing a couple's intimacy and ability to communicate about sex. Education concerning the factors that create normal sexual response and erectile dysfunction can help a couple cope with sexual difficulties. Working with the sexual partner is useful in improving the outcome of therapy. Psychotherapy and behavioral therapy have been reported to relieve depression and anxiety as well as to improve sexual function. However, outcome data of psychological and behavioral therapy have not been quantified, and evaluation of the success of specific techniques used in these treatments is poorly documented. Studies to validate their efficacy are therefore strongly indicated.
Stanley A Brosman, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Association for the Advancement of Science, American Association for Cancer Research, American College of Surgeons, American Medical Association, American Urological Association, Society for Basic Urologic Research, Society of Surgical Oncology, Society of Urologic Oncology, Western Section of the American Urological Association, Association of Clinical Research Professionals, American Society of Clinical Oncology, International Society of Urology, International Society of Urological Pathology
The most common treatment for erectile dysfunction is drugs known as phosphodiesterase-5 (PDE-5) inhibitors. These include tadalafil (Cialis), vardenafil (Levitra), and sildenafil citrate (Viagra). These are effective for about 75% of men with erectile dysfunction. They are tablets that are taken around an hour before sex, and last between 4 and 36 hours. Sexual stimulation is required before an erection will occur. The PDE-5 inhibitors cause dilation of blood vessels in the penis to allow erection to occur, and help it to stay rigid. Men using nitrate medication (e.g. GTN spray or sublingual tablets for angina) should not use PDE-5 inhibitors.
As with most other organ system in the human body, changes and loss of function is normal consequence of the ageing process. This is also true of the endocrine system, specifically the levels of testosterone production from the Leydig cells of the testicle. Accompanying the decrease in testosterone is a decrease in erections which also has a component in decrease in the blood supply to the penis making erection not as frequent and not as rigid compared with a young man’s erectile function. Although these changes are in itself not life threatening, they can impact a man’s relationship with his partner, and also ED may be a harbinger of other undiagnosed conditions such as coronary artery disease (CAD), hypercholesterolaemia or diabetes mellitus.6
Anxiety is particularly pernicious. It triggers the fight-or-flight reflex that sends blood away from the central body, including the penis, and out to the limbs for self-defense or escape. Less blood in the central body means less blood available for erection. Erection dissatisfaction is upsetting, but try to accept it. It’s normal. And when men become anxious about it, erections become less likely.
Not to give your already stressed-out dude one more thing to worry about, but stress is the cause of 20 percent of all erectile problems, from one-off boner blunders to a lingering inability to get and maintain an erection. Of course, sex difficulties are just the tip of the stress-induced health problem iceberg — sustained stress can also lead to insomnia, stomach troubles, chest pains, anxiety, and more severe health issues in the long term.
Certain types of blood pressure medications, antiulcer drugs, antihistamines, tranquilizers (especially before intercourse), antifungals (hetoconazole), antipsychotics, antianxiety drugs, and antidepressants, known as selective serotonin reuptake inhibitors (SSRIs, including Prozac and Paxil), can interfere with erectile function. Smoking, excessive alcohol consumption, and illicit drug use may also contribute. In rare cases, low levels of the male hormone testosterone may contribute to erectile failure. Finally, psychological factors, such as stress, guilt, or anxiety, may also play a role, even when the impotence is primarily due to organic causes.
Picture this: you have the girl of your dreams laid out before you. You’re kissing and things are getting hot and heavy. There’s just one problem: you can’t get hard. Your thoughts quickly turn from “this is amazing” to “this is a disaster,” and before you know it, the story of your floppy dick is making its way down your lover’s social circle. That is if she’s an insensitive gossip. Either way, not being able to get a boner when the time is right is beyond embarrassing.
The most important organic causes of impotence are cardiovascular disease and diabetes, neurological problems (for example, trauma from prostatectomy surgery), hormonal insufficiencies (hypogonadism) and drug side effects. Psychological impotence is where erection or penetration fails due to thoughts or feelings (psychological reasons) rather than physical impossibility; this is somewhat less frequent but can often be helped. In psychological impotence, there is a strong response to placebo treatment.
For younger men, erection problems usually go hand-in-hand with anxiety. It goes something like this. He fancies you and wants to turn you on. But he’s also worried he might not get, or keep, his erection (particularly if he really likes you and/or if this has been a problem in past relationships). These worries mean that when you try and have sex he doesn’t get hard at all, or loses his erection when he tries to penetrate you.
Erectile dysfunction (ED) affects 50% of men older than 40 years,  exerting substantial effects on quality of life.  This common problem is complex and involves multiple pathways. Penile erections are produced by an integration of physiologic processes involving the central nervous, peripheral nervous, hormonal, and vascular systems. Any abnormality in these systems, whether from medication or disease, has a significant impact on the ability to develop and sustain an erection, ejaculate, and experience orgasm.
Occasional successful sexual function and early morning erections do not preclude the possibility of endocrine dysfunction. Since abnormally low levels of testosterone frequently are the primary cause of impotence, it is recommended that determination of the blood level of testosterone be an integral part of the total evaluation of the impotent patient.
You’ve heard of—and probably experienced—the numbing effect alcohol has on your mind, body, and (unfortunately) penis. If you fail to rise to the occasion on a regular basis and you're drinking has gone from occassional weekend binge to a Monday through Friday ordeal, consider cutting back—way back. Heavy drinking proportionately increases your risk of ED, according to research from the Indian Journal of Psychiatry.
The mechanisms by which testosterone plays a role in erectile function are not completely understood. A study evaluating the effect of testosterone on erections in surgically castrated rabbits and control animals, in which the rabbits’ intracavernosal pressures were compared after cavernosal nerve stimulation, determined that castrated rabbits had much lower pressures after stimulation than control rabbits did.  Notably, the pressures increased when castrated rabbits received exogenous testosterone replacement.
Organic Impotence. Diabetes mellitus, thyroid disease, and dysfunction of the pituitary gland or testes can cause impotence, as can certain medications. Other organic causes include arterial ischemia associated with atherosclerosis of the aorta and common iliac arteries, extensive pelvic surgery such as radical prostatectomy, spinal cord injury and other neurologic disorders, and a history of cigarette smoking. Because certain medications can cause impotence, it is recommended that in cases of recent impotence it be determined whether the patient has started on a new drug. The most common offenders are diuretics, antihypertensives, and vasodilators. Alcohol, which sometimes is ignored as a drug, is often a contributor to the problem of impotence.
The primary nerve fibers to the penis are from the dorsal nerve of the penis, a branch of the pudendal nerve. The cavernosal nerves are a part of the autonomic nervous system and incorporate both sympathetic and parasympathetic fibers. They travel posterolaterally along the prostate and enter the corpora cavernosa and corpus spongiosum to regulate blood flow during erection and detumescence. The dorsal somatic nerves are also branches of the pudendal nerves. They are primarily responsible for penile sensation. 
In some cases, ED can be a warning sign of more serious disease. One study suggests ED is a strong predictor of heart attack, stroke, and death from cardiovascular disease. The researchers say all men diagnosed with ED should be evaluated for cardiovascular disease. This does not mean every man with ED will develop heart disease, or that every man with heart disease has ED, but patients should be aware of the link.