...provokes the excitation of several kinds of sensorial receptors located in the skin, mucosa and subcutaneous tissue. This excitation travels through the sensory nerves of the lower abdomen to the sacral spinal cord and start numerous autonomic reflexes (both sympathetic and parasympathetic) which control the selective afflux of blood to these regions, secretion of glands and the contraction of smooth muscles in the sexual organs.

These reactions occur independently of the higher portions of the nervous systems, since they can be provoked, for instance, in tetraplegic individuals who had their spinal cords sectioned by accident at higher levels. In fact, erection and ejaculation can be achieved in such patients, with the result that many are able to have children after their accident.

Sensory cortex and limbic system, in addition to its signalling functions, excite the hypothalamus and other structures which control the autonomic nervous system, with the result that the spinal cord reflexes accompanying the coitus are even more stimulated; in a kind of self-sustaining "loop".

The hypothalamus excite the hypophysis, which release hormone into the blood that is circulating through the body. This hormone is picked up by the ovary and testis, which is thereby stimulated to release a gonadal hormone into blood stream. The hormones, such as oxytocin, FSH and LH will act peripherically to modulate and render the local circuits at the sexual organs more sensitive to the nervous stimuli.

At the same time, the sensorial impulses streaming out of the genitalia, in response to touch and to the local responses (i.e., erection of the penis), travel up the spinal cord to the brain, to the sensory cortex and to the limbic system (the emotional brain) where they elicit conscious perception and pleasurable (emotional) reactions.