Somatomotor penile innervation originates in Onuf’s nucleus in the S2-4 spinal segments. These nerves travel to the ischiocavernosus and bulbocavernosus muscles when activated lead to contraction necessary for the rigid-erection phase. Several animal studies show that stimulation of the somatomotor pathways may also be under sympathetic control, and adrenergic stimulation may lead to contraction of these muscles during ejaculation (13,14). Somatomotor spinal reflexes may also be initiated by genital stimulation. For instance, the well-known bulbocavernosus reflex is evidence this reflex exists; however the clinical significance of its absence in the neurological assessment of ED has not been substantiated (15).
Under normal circumstances, when a man is sexually stimulated, his brain sends a message down the spinal cord and into the nerves of the penis. The nerve endings in the penis release chemical messengers, called neurotransmitters, that signal the corpora cavernosa (the two spongy rods of tissue that span the length of the penis) to relax and fill with blood. As they expand, the corpora cavernosa close off other veins that would normally drain blood from the penis. As the penis becomes engorged with blood, it enlarges and stiffens, causing an erection. Problems with blood vessels, nerves, or tissues of the penis can interfere with an erection.
All of these medicines work by relaxing smooth muscles and increasing blood flow in the penis during sexual stimulation. You should not take any of these medicines to treat ED if you are taking nitrates to treat a heart condition. Nitrates widen and relax your blood vessels. The combination can lead to a sudden drop in blood pressure, which may cause you to become faint or dizzy, or fall, leading to possible injuries.
Psychological factors — Psychological issues such as depression, anxiety, guilt or fear can sometimes cause sexual problems. At one time, these factors were thought to be the major cause of impotence. Doctors now know that physical factors cause impotence in most men with the problem. However, embarrassment or "performance anxiety" can make a physical problem worse.
Conditions associated with reduced nerve and endothelium function (eg, aging, hypertension, smoking, hypercholesterolemia, and diabetes) alter the balance between contraction and relaxation factors (see Pathophysiology). These conditions cause circulatory and structural changes in penile tissues, resulting in arterial insufficiency and defective smooth muscle relaxation. In some patients, sexual dysfunction may be the presenting symptom of these disorders.
Melanocortin receptor agonists were found to induce erections serendipitously. A study investigating the dermatologic use of Melanotan-II (MT-II) was found to generate erections unexpectedly leading to the development of MTII derivatives for ED treatment (120). MT-II was initially used to induce pigment changes in the skin for artificial tanning but has been suspected to induce melanoma, however (121).
Diabetes. Erectile Dysfunction is common in people with diabetes. An estimated 10.9 million adult men in the U.S. have diabetes, and 35 to 50 percent of these men are impotent. The process involves premature and unusually severe hardening of the arteries. Peripheral neuropathy, with involvement of the nerves controlling erections, is commonly seen in people with diabetes.
Malleable implants usually consist of paired rods, inserted surgically into each of the corpora cavernosa. The rods are stiff, and to have an erection, one bends them up and then when finished with intercourse one bends them down. They do not change in length or width. The malleable implants are the least mechanical and thus have the lowest risk of malfunction. However, also have the least "normal appearance."
In prescribing sildenafil, a doctor considers the age, general health status, and other medication(s) the patient is taking. The usual starting dose for most men is 50 mg, however, the doctor may increase or decrease the dose depending on side effects and effectiveness. The maximum recommended dose is 100 mg every 24 hours. However, many men will need 100 mg of sildenafil for optimal effectiveness, and some doctors are recommending 100 mg as the starting dose.
When you become aroused, your brain sends chemical messages to the blood vessels in the penis, causing them to dilate or open, allowing blood to flow into the penis. As the pressure builds, the blood becomes trapped in the corpora cavernosa, keeping the penis erect. If blood flow to the penis is insufficient or if it fails to stay inside the penis, it can lead to erectile dysfunction.
Before taking any medication for erectile dysfunction, including over-the-counter supplements and herbal remedies, get your doctor's OK. Medications for erectile dysfunction do not work in all men and might be less effective in certain conditions, such as after prostate surgery or if you have diabetes. Some medications might also be dangerous if you:
Tests such as the bulbocavernosus reflex test are used to determine if there is sufficient nerve sensation in the penis. The physician squeezes the glans (head) of the penis, which immediately causes the anus to contract if nerve function is normal. A physician measures the latency between squeeze and contraction by observing the anal sphincter or by feeling it with a gloved finger inserted past the anus.
According to a review of all randomized controlled trials evaluating sildenafil by the American Urological Association (AUA) Consensus Panel on Erectile Dysfunction, 36% to 76% of patients receiving the drug were "able to achieve intercourse" during treatment. For tadalafil, four randomized controlled trials revealed that 11% to 47% of patients were "able to achieve intercourse." Similar efficacy has been observed with vardenafil, although studies are fewer.19 A meta-analysis published in 2013 clearly demonstrated increased efficacy over placebo for all PDE5 inhibitors.24 Head-to-head comparison suggested that tadalafil outperforms sildenafil on validated measures of erectile dysfunction, including the international index of erectile function and sexual encounter profile-2 and -3.
Yes, the vacuum device is effective. In fact, with use of the vacuum device, 88% of men will have an erection that is satisfactory for completion of sexual activity. The vacuum device may be the only therapy that is effective after the removal of a penile prosthesis. Patients also use vacuum devices as part of penile rehabilitation after radical prostatectomy to help preserve the tissue of the penis and prevent scarring within the penis and loss of penile length. Its use, however, is limited by the mechanical nature of it and the time taken to pump the device and apply the band. Sex partners may complain of the penis being cool to touch.
ED usually has something physical behind it, particularly in older men. But psychological factors can be a factor in many cases of ED. Experts say stress, depression, poor self-esteem, and performance anxiety can short-circuit the process that leads to an erection. These factors can also make the problem worse in men whose ED stems from something physical.
Erectile dysfunction is the inability to develop or maintain an erection that is rigid enough to allow penetration of the vagina, and therefore functional sexual intercourse. Generally, the term erectile dysfunction is applied if this occurs frequently (75% of the time) over a significant period if time (several weeks to months). If this is the case, the term impotence may also be used.
A number of herbs have been promoted for treating impotence. The most widely touted herbs for this purpose are Coryanthe yohimbe (available by prescription as yohimbine, with the trade name Yocon) and gingko (Gingko biloba), although neither has been conclusively shown to help the condition in controlled studies. In addition, gingko carries some risk of abnormal blood clotting and should be avoided by men taking blood thinners such as coumadin. Other herbs promoted for treating impotence include true unicorn root (Aletrius farinosa), saw palmetto (Serenoa repens), ginseng (Panax ginseng), and Siberian ginseng (Eleuthrococcus senticosus). Strychnos Nux vomica has been recommended, especially when impotence is caused by excessive alcohol, cigarettes, or dietary indiscretions, but it can be very toxic if taken improperly, so it should be used only under the strict supervision of a physician trained in its use.
Ultrasound with Doppler imaging (ultrasound plus evaluation of blood flow in the arteries and veins) can provide additional information about blood flow of the penis and may help in the evaluation of patients prior to surgical intervention. This study is typically performed after the injection of a chemical that causes the arteries to open up, a vasodilator (prostaglandin E1), into the corpora cavernosa in order to cause dilation of blood vessels and promote blood flow into the penis. The rate of blood flow into the penis can be measured along with an evaluation of problems with compression of the veins.
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.