Читать книгу Saving Your Sex Life: A Guide for Men With Prostate Cancer - John P. Mulhall - Страница 9

The simplest way to think of an erection is to think of a simple hydraulic process like the inflation of a bicycle tire. To inflate a bicycle tire, you need a hose to transfer air into the tire, and when the hose is removed, there is a valve that is closed tightly to maintain that air pressure. I have already described the two erection arteries that carry blood into the penis (the hoses), and as the blood fills up the lacunar spaces and they expand, the previously mentioned emissary veins get trapped and compressed (the valve). The valve mechanism is critical to the generation of good rigidity and maintenance of an erection. Indeed, the most common cause of men losing an erection in the middle of intercourse is because this muscle, under adrenaline control, contracts precipitously allowing the veins to carry blood out of the penis rapidly.

So for erection to function, there are a number of key elements that need to be in working order. Firstly, the arteries need to be healthy. Next, the nerves need to be functioning. And finally, the erectile tissue needs to be in good condition. Arterial blockage will reduce the blood flowing into the penis, and this will lead to erection dysfunction. Cavernous nerves that are injured will not supply nitric oxide to allow an erection to occur, and erection tissue which is injured due to diabetes, cigarette smoking, radiation therapy or the chronic absence of erections will also lead to erectile dysfunction.

The nerves are not the only source of nitric oxide, as the endothelium also supplies nitric oxide and is a key regulator of maintenance of erection. In addition to erectile smooth muscle needing to be healthy, so too must the endothelium. It is now known that conditions such as high blood pressure, high cholesterol, diabetes, and cigarette smoking, all cause endothelial dysfunction and this is why these men have a higher incidence of erectile dysfunction than the general population. There are more than 20 neurotransmitters (chemicals that come from the nerves) that are involved in erectile function, but the most important ones are nitric oxide, which is a pro-erection chemical, and adrenaline, which is the world’s most potent anti-erection chemical. Adrenaline, which is known as the “fight or flight” hormone, is released by the adrenal glands during periods of stress, such as being in a fight or running away from something. Increased adrenaline levels are noted in men during high stress, chronic fatigue, and when they are anxious, irritated, annoyed, upset, or worried. This is why stress is a cause of erectile dysfunction.

When a man is aroused, areas within the brain and within the spinal cord increase nerve signals, which causes increased blood flow through the cavernosal arteries. These signals also cause relaxation of the erectile tissue with an increase in the size of the lacunar spaces. As the blood flows into these spaces, the erectile tissue expands in a three-dimensional fashion, compressing the emissary veins, and a rigid erection occurs. Upon removal of the sexual stimulus (generally after orgasm), the nitric oxide level drops precipitously and adrenaline assumes its usual role of keeping the penis flaccid. Then the erectile tissue contracts, blood makes its way back into the general circulation, and erection dissipates.