Men’s morning erections are caused by parasympathetic nerve excitation, if the morning erection is abnormal, it is considered to be caused by high blood pressure, long time holding urine and other factors. Men’s morning erection will have a normal physiological reaction in the middle of sleep, morning erection refers to the penis in the unconscious state of natural erection, generally men will be in the morning 4 to 7 o’clock morning erection. Morning erections are caused by the increased excitability of the parasympathetic nerves in the morning and the decreased excitability of the sympathetic nerves. This is because parasympathetic excitability causes the corpus cavernosum of the penis to fill with blood and the blood vessels of the penis to dilate, thus causing an erection. If men have erectile dysfunction or morning erection disappears, it is mostly considered to be caused by high blood pressure, holding urine for a long time, excessive mental stress, excessive smoking and drinking, as well as lumbar disc herniation, spinal cord injury and other factors. It is normal for a man to have a morning erection in the morning, and it is not a morbid phenomenon. If there is no morning erection, it does not mean that there is a problem with male function, but also according to other symptoms for comprehensive judgment.