When a man is sexually stimulated by sight, thought, or touch, the brain sends signals that relax the smooth muscles around the arteries that supply blood to the spongy and cavernous bodies. The veins draining the bodies can't keep up, resulting in swelling. As the swelling reaches the limit of the penile skin, the penis becomes firm. The pressure of the spongy and cavernous bodies against the skin partially closes the veins, helping to maintain the erection. Erection continues until the signals from the brain stop, but erections are not consistent; waking and waning are normal, even during intercourse.
Erection can occur throughout life, happening before birth and into the 90's in healthy men. Nocturnal erections occur during all male dreams (regardless of what the dream is about), unless the man has physical problems (this is the easiest way to determine if impotence is physical or emotional in nature). The so called "morning erection" is the result of being wakened during, or just after a dream; and it can be a very persistent erection. While a morning erection is not a sign of arousal, it's presents and the pleasurable sensations it can create may result in arousal.
Men have only very limited control over their erections. During puberty the young man is often embarrassed by erection in public settings, but he gradually becomes able to suppress erections when the stimulation is mild. Likewise, it is impossible to "will" an erection, although sexual thoughts can cause erection. During prolonged foreplay a man's erection may go away; this is normal, and is not a sign of lessening interest.
General health and physical exhaustion can affect erection; when very tired, a man may be able to have only a partial erection, but still be able to climax. Erection is lost in two stages; the initial stage is very quick, but usually leaves the penis firm enough to continue intercourse. The second stage is somewhat slower and is effected by a variety of things including age (which tends to speed it), and arousal level before climax, with higher (or longer) pre-climax arousal generally resulting in slower lose of erection
Although the head (or glands) of the penis is very sensitive to touch, touch alone does not bring about an erection. The epicenter responsible for such essential arousal is actually within the brain. Only after the brain receives visual, audio or mentally stimulating input will it transmit (via the central nervous system) instructions to the smooth muscles along the penis to relax. Specifically the release of nitric oxide in the corpora cavernosa relaxes the smooth muscles. At the same time, the artery to the penis widen to twice its diameter, increasing the blood flow sixteen-fold, and the veins which carry blood away from the penis are blocked. As a result, the two spongy-tissue chambers in the shaft of the penis fill with blood and the penis becomes firm. The corpora cavernosa, acting like a sponge, fill with blood. In fact, the corpora absorb up to eight times more blood than when the penis is flaccid. As your penis swells and lengthens, the filled corpora cavernosa press against the veins. The veins surrounding the chambers are squeezed almost completely shut by this pressure. The veins are unable to drain blood out of the penis and so the penis becomes rigid and erect. This condition normally keeps this erection firm enough for intercourse.
At this most basic level this function is considered to be normal if a man is able to maintain his erection sufficiently long to engage in satisfying intercourse and the subsequent ejaculation. The length of time a man might stay continuously erect can be on the average be about 30 - 45 minutes. Of course the duration of his erection vary greatly, in which case it may be a shorter or a great deal longer. After ejaculation or cessation of further stimulation to the penis itself or to the brain excess blood will be allowed to drain away, while the level of blood flow into the penis returns to normal. The penis once again becomes flaccid as it loses the built up pressure.
Erectile quality or intensity may depend on the nature in which the brain is stimulated. Acts as simple as kissing or "petting" are at times sufficiently arousing to bring about an erection. Viewing a sexually titillating movie or photographs will arouse most men to erection. Beyond this the particular nature of erotic images will have varying effects, as men tend to have a broad range of sexual tastes and desires. While some men may become highly aroused by mundane stimulation, others thrive on fetishes.
The male libido is often receptive to a great variety of stimulation. To consider a man sexually dysfunctional solely by measuring his arousal during intercourse, with a long term partner, is simply too limited as well as illogical. Certainly there are men who are not only fulfilled, but thrive in life-long monogamous relationships. This confirms the notion that there is great variation between the needs and sensibilities among men. It would be a mistake however to insist that all men can achieve the same purpose, blissfully maintaining a long-term relationship, which is both sexually and emotionally satisfying.
What if things aren't quite working that way. There are a number of conditions which may diminish or otherwise influence this process, these are known and considered under one very general catch all term: Erectile Dysfunction, which is technically defined as "the inability to achieve or maintain an erection sufficient for sexual intercourse". This is one of the most common sexual ailments in men. Although erectile dysfunction can be primarily psychological in origin, for most men it's more likely a physical disorder, often with some psychological overlay. While some men assume that erectile failure is a natural part of the aging process and tolerate it; others find it devastating. Withdrawal from sexual intimacy because of fear of failure can damage relationships and have a profound effect on overall well being for the couple.
The Massachusetts Male Aging Study measured several health related variables in 1290 men aged 40 to 70 years. Erectile dysfunction was very common. Fifty two per cent of the men reported some degree of impotence-mild in 17.1%, moderate in 25.2%, and complete in 9.6%. Complete impotence was reported by 5% of men at 40 years of age and 15% at 70 years of age.
Over the past decades, the medical perspective on the causes of impotence has shifted. Common wisdom used to attribute almost all cases of impotence to psychological factors. Now investigators estimate that between 70% and 80% of impotence cases are caused by medical problems. It is often difficult to determine if the cause of erectile dysfunction is physical or psychological, or even some combination. The following may be helpful in understanding the difference.
* Psychological impotence tends to be abrupt and related to a recent situation. The invidual may be able to have an erection in some circumstances but not in others. The inability to experience or maintain an erection upon waking up in the morning suggests that the problem is physical rather than psychological.
* Physical impotence occurs gradually but continuously over a period of time. If impotence persists over a three-month period and is not due to a stressful event, drug use, alcohol, or medical conditions, the individual may needs to seek medical attention from a urologist specializing in impotence.
In virtually every case of impotence, there are emotional issues that can seriously affect the man's self-esteem and relationships, and may even cause or perpetuate erectile dysfunction. Many men tend to fault themselves for their impotence even if it is clearly caused by physical problems over which they have little control.
Anxiety has both emotional and physical consequences that can affect erectile function. It is among the most frequently cited contributors to psychological impotence. Anxiety over sexual performance is often referred to as performance anxiety and may provoke an intense fear of failure and self-doubt. It can sometimes set off a cycle of chronic impotence. In response to anxiety, the brain releases chemicals known as neurotransmitters that constrict the smooth muscles of the penis and its arteries. This constriction reduces the blood flow into and increases the blood flow out of the penis. Simple stress may even promote the release of brain chemicals that negatively affect potency in a similar way.
Depression is strongly associated with erectile dysfunction. In one study, 82% of men who reported moderate to severe erectile dysfunction also had symptoms of depression. Depression can certainly reduce sexual desire, but it is often not clear which condition came first.
Problems in Relationships often have a direct impact on sexual functioning. Partners of men with erectile dysfunction may feel rejected and resentful, particularly if the affected man does not confide his own anxieties or depression. Both partners commonly experience guilt for what they each perceive as a personal failure. Tension and anger frequently arise between people who are unable to discuss sexual or emotional issues with each other. It can be very difficult for the man to perform sexually when both partners harbor negative feelings.
Socioeconomic Issues like losing a job or having lower income or education increases the risk for impotence.
Smoking (particularly heavy) is frequently cited as a contributory factor in the development of impotence.
Alcohol has also been implicated in causing impotence. In small doses, alcohol releases inhibitions, but in doses larger than one drink, it can depress the central nervous system and impair sexual function.
Lack of Frequent Erections deprive the penis of oxygen-rich blood. Without daily erections, collagen production increases and eventually may form a tough tissue that interferes with blood flow. The spontaneous erection men experience while sleeping or awake may be a natural protection against this process.