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Penile erection is managed by two mechanisms: the reflex erection, which is achieved by directly touching the penile shaft, and the psychogenic erection, which is achieved by erotic or emotional stimuli. The former uses the peripheral nerves and the lower parts of the spinal cord, whereas the latter uses the limbic system of the brain. In both conditions, an intact neural system is required for a successful and complete erection. Stimulation of the penile shaft by the nervous system leads to the secretion of nitric oxide (NO), which causes the relaxation of smooth muscles of corpora cavernosa (the main erectile tissue of penis), and subsequently penile erection. Additionally, adequate levels of testosterone (produced by the testes) and an intact pituitary gland are required for the development of a healthy erectile system. As can be understood from the mechanisms of a normal erection, impotence may develop due to hormonal deficiency, disorders of the neural system, lack of adequate penile blood supply or psychological problems. Restriction of blood flow can arise from impaired endothelial function due to the usual causes associated with coronary artery disease, but can also be caused by prolonged exposure to bright light. viagra find online pages edinburgh free buy viagra online Erectile Dysfunction Basics: Erectile dysfunction, commonly referred to as ED, is the inability to achieve and sustain an erection suitable for sexual intercourse. This condition is not necessarily considered normal at any age and is different from other problems that interfere with sexual intercourse, such as lack of sexual desire and problems with ejaculation and orgasm. g postmessage propecia smiley online propecia online buy levitra generic Other blood tests: Evaluation for hemochromatosis, lupus, scleroderma, zinc deficiency, sickle cell anemia, cancers (leukemia, colon cancer) are some of the other potential tests that may be performed based on each individual's history and symptoms. Penile injections: The injection of drugs such as alprostadil directly into the tissues of the penis to trigger an erection was more common before the advent of new drugs such as sildenafil. The drugs relax muscles and increase blood flow to create an erection. They are also available as pellets to insert in to the urethra (the opening at the tip of the penis). How does an erection normally occur? The neurotransmitters which are released in the penis cause another chemical to be made called cyclic guanosine monophosphate (cGMP). An increase of cGMP causes the arteries in the penis to dilate (widen). This allows extra blood to flood into the penis. The rapid inflow of blood causes the penis to swell into an erection. The swollen inner part of the penis also presses on the veins nearer to the skin surface of the penis. These veins normally drain the penis of blood. So, the flow of blood out of the penis is also restricted, which enhances the erection. Medication (tablets taken by mouth) In 1998, the first tablet to treat ED was launched. This made a huge impact on the treatment of ED. There are now four different tablets licensed in the UK to treat ED: Three of the tablets work by increasing the blood flow to your penis. They do this by affecting cGMP, the chemical involved in dilating (widening) the blood vessels when you are sexually aroused (described above). They are sildenafil (trade name Viagra�), tadalafil (trade name Cialis�), and vardenafil (trade name Levitra�). You take a dose before you plan to have sex. Because of the way they work, these medicines are called phosphodiesterase type 5 (PDE5) inhibitors. ED can also be associated with bicycling due to both neurological and vascular problems due to compression. The increase risk appears to be about 1.7 fold. cialis online prescriptions buy cialis online