While an erection may appear to be fairly simple and straightforward, it is actually one of the most complex and impressive functions of the human body. The process of achieving an erection is controlled by either the central nervous system or the autonomic nervous system, depending on the type of stimulation involved.
For men the most common types of stimulation are visual, auditory, olfactory, imaginary and tactile. These are the stimuli that tell the cerebral cortex to start the erection process. Erectile centers in the lumbar and sacral regions of the spinal cord continue the process by signaling the nerves located in the pubic area to begin the release of nitric oxide. This chemical compound functions as a signaling molecule to transmit information from one cell to another.
When nitric oxide is released, arteries that supply blood to the penis dilate which allows a greater supply of blood to enter the penis. This blood engorges the two sponge-like and expandable tissues known as the Corpora Cavernosa. The tubular structure located beneath the Corpora Cavernosa through which urine and semen pass, called the Corpus Spongiosum, also becomes slightly engorged with blood although not to the extent that the Corpora Cavernosa does.
Once enough blood has flooded the penis, the arteries contract, normal blood flow is resumed and the blood inside the penis is trapped and prevented from leaving the area. This process can occur in both the presence and absence of external stimuli and is handled by the autonomic nervous system with minimal input from the central nervous system. Once stimulation ends, the autonomic nervous system directs the arteries to constrict and blood is forced out of the penis.
The cerebral cortex, while not always directly involved in the types of stimulation that cause erections, can play a major role in prolonging and terminating one. Since the mind is so powerful and even a single thought is often capable of ending an erection, men wishing to sustain an erection should take care not to dwell on things that would negatively effect arousal.
Posted by PRS
Tuesday, May 15th, 2007