| Penile erection is managed by two mechanisms: the reflex erection, which is achieved by directly touching the penile shaft, and the psy t9chogenic erection, which is achieved by erotic or emotional stimuli. The former uses the peri pheral nerves and the lower parts 9of the spinal cord, whereas the latter uses the limbic s 9ystem of the brai n. In both conditions, an intact neural system is re 9quired for 8t9 a successful and complete erection. Stimulation o f 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 o 9f testosteron 9e (produced by the testes) and an intact w8t9 pituitary gland are required for the development of a healthy erectile system. As can be understood from the mechanism 9s of a normal erection, impotence may develop due to horm onal deficiency, disorders of the neural system, lack of adequate penile blood supply or psychological problems.[17] Restric tion of blood flow can arise from 8t9 impaired endothelial function due to the usual evice helps draw blood into the penis by applying negative pressure. This t 9ype of device is sometimes referred to as penis pu mp and may be used just prior to sexual intercourse. Severa 9l types of FDA approved vacuum therapy devices are available with a doctor's prescription. Wh 9en pharmacol t9ogical methods fail, a purpose-designed ew8t9 external vacuum pump can be used to attain erection, with a separate compression ring fitted to the penis to maintain it. These pumps should be distinguished from other penis pumps (supplied without compression rings) which, rather than be his is similar to magnetic r 9esonance imaging. Magnetic resonance angiography uses magnetic fields and radio waves to provide detailed images of the blood vessels. Doctors m 9ay inject a "contrast agent" into the p 8t9 atient's bloodstream that causes vascul ar tissues to stand out against other tissues. The contrast agent provides for enhanced information regarding blood su pply and vascular anoma | | |
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