Erection is one of the most impressive functions of the human body that we can observe on a regular basis and without the aid of devices. While the process itself may look pretty simple and straightforward, it is anything but that. Whether we’re talking about the penis or the clitoris, the process is largely the same and just as complex since it is guided by either the central nervous system or by the autonomic nervous system, depending upon the type of stimulation encountered.
The most common type of stimulation for men is based on visual, auditory, olfactory, imagined, or tactile stimuli that tell the cerebral cortex to begin the erection process. The erectile centers located in the lumbar and sacral regions of the spinal cord then tell the nerves in the pubic area to start releasing nitric oxide. Nitric oxide is a chemical compound widely used by all mammals as a signaling molecule in order to transmit information from one cell to another.
When the nitric oxide is released, the arteries that supply the penis with blood dilate and allow a bigger than usual quantity of blood to enter the penis. The blood goes into the Corpora Cavernosa, the two sponge-like tissues that are designed to expand in size and hold as much blood as possible. The Corpus Spongiosum, the tubular structure located just below the Corpora Cavernosa through which urine and semen pass, also becomes slightly engorged with blood, but not nearly as much as the Corpora Cavernosa.
As soon as enough blood has entered the penis, the arteries contract in order to return to the normal flow of blood, thus preventing the blood inside the penis from leaving the area. The same system is used in the case of mechanical stimulation of the penis and in the absence of external stimuli. The entire process is handled by the autonomic nervous system (ANS) with minimal input from the central nervous system. When the stimulation ends, the ANS makes the arteries constrict and forces blood out of the penis.
Although the cerebral cortex is not involved in every type of stimulation that causes erection, it, nevertheless, can put an end to any erection if it judges that the situation requires such action. This is why men and women have to avoid things that can kill the mood and turn them off.