When a man is excited by the auditory, visual, olfactory and thinking, imagination, etc. of the sexual content, and stimulates the cerebral cortex through the thoracic and erectile center of the spinal cord, it acts on the corpus cavernosum and expands the arterial blood vessels. Inflow into the corpus cavernosum; when the venous blood vessels contract and the blood flowing out of the corpus cavernosum is reduced, the blood is fully retained in the abundant blood vessels and blood sinus of the sponge, causing the penis to rapidly develop a psychological erection. Conversely, when the arterial blood vessels contract, the blood flowing into the corpus cavernosum is reduced; When the venous blood vessels dilate and the abundant blood flow remaining in the sponge rapidly returns, the penis will return to weakness. When the external genitalia is subjected to local stimuli such as direct touch, walking friction or receiving internal stimulation of the rectum and bladder, it can cause a reflex erection, which stimulates its sexuality by stimulating the lower erectile center of the medullary spinal cord. Realized after the excitement. Penile erection is natural, and the male fetus can erect in the womb. When a boy urinates after birth, he may also get an erection hardening. Sometimes lying there peeing can make the urine spray directly onto the adult’s face like a spring, often bringing unexpected laughter and joy to the parents who are changing diapers, but The erection at this time does not have any meaning of “sex”. Any stimulation of the genital itself can cause reflex erections, which regulate through the pudendal nerve and the palpebral erection center. Psychological and physiological stimuli can work alone, interact with each other, and be involved in sexual activity. For example, when the spinal cord injury occurs above the thoracolumbar region, the patient can only have an erection in the case of physical stimulation of the genitals, and the ability to psychological erection disappears. When motor neuron injury occurs at the level below the thoracolumbar region, stimulating the genitals can not cause erections, and 24 to 57% of patients still have psychological erections, that is, psychological stimulation can be transmitted through the thoracolumbar pathway. When the spinal cord injury occurs at the waist 2 to 骶1, both psychological and reflex erections exist, but the two cannot be coordinated, and it is impossible to achieve ejaculation orgasm through genital stimulation. In addition to psychological erections and reflex erections, normal men also have a nighttime erection. Men’s sleep is always in the alternating between fast-moving eye sleep and slow-motion eye sleep, and also experiences erection–weakness–erection– ─ The weak physiological process, which is medically known as the penile night erection, is a normal physiological process for healthy men. In general, men have 4 to 6 times a night, 20 to 40 minutes of erection every time, a total of up to two and a half hours. This is because the brain always suppresses the sexual reaction during the day, otherwise the man will inevitably encounter embarrassing situations from time to time, but after asleep, the inhibition function of the brain disappears, and the penis spontaneously has an erectile reaction, which is completely normal. no need to worry. The time, frequency, and hardness of night erections decrease with age, and puberty is the strongest until about 20 years old. Whether it is a psychological or a reflective erection, the penis quickly returns to normal after the external stimuli are removed. Night erections are no exception. When the penis is erected for a while, it will definitely weaken down. Because the blood stays in the sponge for a long time, the blood will be deprived of oxygen and accumulate a large amount of metabolic waste, which is not good for the organization. In severe cases, necrosis will occur. There is a disease with abnormal penile erection. The patient shows that the penis has been swollen for 4 to 6 hours, hard, painful, and grayish gray. This is an emergency in urology and needs to be urgently treated in the hospital as soon as possible. Therefore, the penis is not an erection all night, but there must be a relaxation. Early morning erection is a clinically significant physiological phenomenon. Some doctors have studied this phenomenon and found that during the illness, the erection in the morning will weaken or disappear. After the physical recovery, the morning erection will recover. Therefore, early morning erection can be used as a reference indicator for men’s health. The presence or absence of an erection in the early morning can also be used as a reference indicator for judging the state of sexual function in men.