Chemical substances are often imagined to be perceived only through the senses of smell and taste. Yet this is not the case, because there are also at least two known systems: pain receptor nerves and the vomeronasal organ.
(Figure 17) Side: The location of the vomeronasal organ (VNO) in the nose.
Throughout the nasal cavity, including the olfactory region, are dispersed the ends of pain-receptor nerves that react to stimuli that lead to feelings of pressure, pain, heat and cold. For example, these nerves transmit to the brain signals that cause the sharp, burning sensation of ammonia. Were it not for the pain receptors in your nose, you could not detect various gasses that are harmful to your health. Thanks to the design in question, however, unfortunate consequences that might result in injury, or even death, are avoided.
(Figure 18) Below: The cellular organization in the vomeronasal organ.
In comparison with scent receptors, these nerves are less sensitive and are thought to play an important complementary role in scent perception. Menthol is known to produce a cooling sensation in normal concentrations, but a hot one at high concentrations. The special design at the ends of the pain-receptor cells allows us to perceive this difference.
Some scent particles produce no effect in the olfactory region. These special chemical signals are known as pheromones. A special organ in the nose has been created to detect pheromones. Known as the vomeronasal organ (VNO), this structure is of a tube- shaped, about 1 millimeter (0.04 inch) in length, and located in the inner part of the nose, just above the cartilage dividing the two nostrils. (Figure 17) It is a different sensory organ whose chief function is to receive the messages carried by pheromones, convert them into a form the brain can understand, and then forward them by means of special nerves directly to the relevant brain regions. (Figure 18) This organ's functions are not yet fully understood, and are the subject of debate among scientists.
But it has already emerged that the VNO is of vital importance to some insects and animals. For example, the social, reproductive and hunting of snakes with damaged VNOs becomes impaired. Rats with no sexual experience and whose VNOs were surgically removed were unable to mate, although their other organs functioned perfectly.
We know for certain that there are unknown mechanisms in the olfactory region in our noses. For example, consider the relationship between color and odor sensitivity. This region is light yellow in human beings but brown in dogs. The color element is thought to influence scent detection capacity, although the link between them is not understood.
Every new piece of scientific research lets us become better acquainted with the marvels of creation. Maybe as-yet-unknown perfect systems in our noses will be brought to light. These will be a new means of giving thanks in the manner that we should to God, the Lord of boundless affection and compassion Who created them.
As you sit reading these lines, you have practically no awareness of the presence of the clothes you wear, despite their close contact with your skin.
You feel clothes when you first put them on, but that feeling soon disappears, because receptors in your skin stop sending messages to the brain. Were it not for this marvelous system, everyday actions such as wearing clothes would become intolerable. You would also be unable to perceive other signals because your clothes distracted you, and your life would become very difficult indeed.
A similar process applies with the sense of smell. When you enter a restaurant, you immediately perceive the cooking aromas. A short while later, however, you become unaware of them. Yet there has been no reduction in the level of those heavy smells. You have simply grown accustomed to them. A special mechanism known as adaptation causes this change in sensitivity, although the aroma itself does not change in the least.
A cook's sensitivity to smells in the kitchen soon declines in a matter of minutes. In this way, he is not bothered by the intense aromas constantly reaching him and is also able to immediately detect any new odor—such as a gas leak or something burning.
To grasp the importance of this mechanism, consider the cooks who work in a restaurant kitchen full of dense odors. If their sensitivity to the ambient smells did not decrease, their situation would be exceedingly uncomfortable. And their scent receptors, kept constantly busy, might be unable to detect any dangers—a gas leak, for example.
Frank Zufall, known for his research in this field, states that scent adaptation contains mechanisms that are so complex that the processes at the molecular level are still not fully understood. There are thought to be at least three different scent-adaptation mechanisms in the scent receptor cells. In addition, there must also be centers in the brain to monitor the sense organs that either transmit or halt this information.
In that case, how did the scent-receptor and brain cells, themselves consisting of atoms like carbon, nitrogen and oxygen, come to develop an adaptation system, whose details are still unknown? How do they know when, and when not, to go into action? How do they act in the very best manner on your behalf, without your becoming involved in any way?
The answers are clear: This adaptation system in scent perception is one of the innumerable examples of the superior design flawless planning and perfect order to be seen everywhere in the universe. There is absolutely no doubt that such a marvelous order leaves no room for chance. Every component of these flawless systems in our bodies is far too perfect to be accounted for in terms of coincidence.
As it is revealed in the Qur'an, "He directs the whole affair from heaven to Earth . . . ." (Surat as-Sajda: 5)