What happens when the penis is hard?

Male erectile dysfunction is a complex process involving multiple aspects of the brain, hormones, emotions, nerves, muscles, and blood vessels. Erectile dysfunction may be related to one or more of the above causes. Psychological impotence accounts for about 85%-90% of the total number of impotence, is the most common sexual dysfunction disease, non-organic lesions and cerebral cortex to enhance the inhibition of sexual excitement, and spinal cord erectile center excitability decreased, that is, the so-called functional reasons. It can also be chronic disease, physical weakness or overwork is caused by physical or mental work caused by physical weakness or neurasthenia. Another factor is from mental factors, such as fear of pregnancy, bad sexual environment, husband and wife cold feelings, or think that there are problems with sexual function due to excessive ejaculation, masturbation, or even fear of lack of sexual knowledge, or fear of blame from the woman.