What causes penis erection?

Erection occurs at the moment when blood fills penis and a zone, which is between men’s legs. But firstly the brain and the spinal cords send signals which are transmitted to the parasympatic nervous system. (a component of the involuntary nervous system)

THE WAY THE NERVOUS SYSTEM RULES AND TRIGGERS THE ERECTION

The following things happen to trigger and control the erection:
-Genital zone and sensorial bodies are being stimulated. Impulses run through nerves and the spinal cords to the brain. At the end of the journey they achieve the upper zones of the brain. The task of the brain is to recognize the impulses and send them as something sexual. But also the thoughts which brain produces may be recognized as something sexual.

-After recognition of sexual impulses, the signals are sent towards the limbic system, which is located at the lower zone of the brain. Limbic system is known to produce the feeling of excitement.
-Then the limbic system sends signals to the spinal cord and out to the genital zone where they go through special kind of nerves which are titled nervi erigentes. They constitute a part of the whole nervous system
-After achieving the penis and the genital area, engorgement between the men’s legs is observed.
-There is no need in stimulating the penis or the genital area to achieve the brain to cause the erection. Spinal cords’ areas can recognize the stimulation and get excitement. After that, the spinal cord sends impulses back to the genital zone.
-The erection can stimulate the sensorial bodies within the genital zone mechanically. The process of the erections is self enforcing.

ANATOMY OF THE ERECTION

There are three bodies in the penis consisting of the set of elastic blood vessels with small muscles on the walls. These bodies are called the erectile bodies. There also exist 2 paired bodies which are located at the upper side of the urethra, which are called corpora cavernosa. And one body is located around the urethra. It’s titled corpus spongiosum.
The ability of vessels muscles is to press the volume or relax, making vessels widen. Vessels circulate blood around erectile bodies. Moreover, they can relax and constrict to regulate blood flow. The erectile zones are located not only in the penis, but also between legs, near the anal area.

WHAT OCCURS WHEN THE ERECTION HAPPENS

Below there are events which occur in genital zone when the erection happens:
-After signals sent by the brain and the spinal cords achieve the penis nerve ends and the genital area, such a component as nitric oxide is released
- Then nitric oxide gets located all over the penis and the genital area. And after that it triggers such reactions:
-Those blood vessels which run to the erectile bodies get relaxed. Due to this, greater amount of blood runs to the penis.
-Those blood vessels which run from the erectile bodies strengthen. Due to this, blood doesn’t leave the genitals.
-Then smooth muscles, around the erectile bodies, relax making vessels widen.
-The blood, which runs to the erectile bodies, is filling up the vessels of these bodies enlarging their volume.
-As a result, the inflated bodies harden and straighten influencing the penis and making it erect.
-When full erection is achieved, the penis becomes hard and stands straight, because the area which is between the legs is filled with blood fixing the phallus