Phantosmia - The Olfactory System

The Olfactory System

The olfactory system is highly connected to the limbic system and gustatory system. An example of the relation between the systems is the common cold. When an individual suffers from a cold, the ability to smell and taste is co-affected. Furthermore, many smells of food tell us if they food item is safe to consume or not. As foods with unpleasant smells may be poisonous or harmful to the body. Although this relation exists, the olfactory system is not affected by the gustatory system. The two systems are independent and have different neuronal pathways to the brain. It is thought that the olfactory system and gustatory system were originally one and then became defined and distinct over the evolutionary time period.

Olfactory chemicals also have a strong influence on the cerebrum where the emotions are contained thus it is also related to the limbic system. The olfactory system gave rise to the limbic system. It has also been found that the olfactory and limbic system have evolved into two different structures known as the olfactory stratium and the corpus stratium. In a study done by Dr. Alan Hirsch, it was found that gamblers spent from 33-55% more money and time gambling when they were exposed to a certain odor compared to those that were not exposed to the odor.

The limbic system structures that are responsible for memory: the hippocampus and the amygdala are part of the rhinencephalon. The nerve fibre that connects the olfactory mucosa to the olfactory bulb ends in this region of the brain.

The olfactory bulb is composed of several million neurons. All olfactory messages from the olfactory limbic system are received here and are carefully organised. After this the message or signal is transmitted to other regions of the brain. Insects do not have an olfactory bulb. The olfactory nerve is composed of nasal nerve cells, these nerves link the nose and the olfactory bulb together. In many cases such as accidents, damage due to surgery, infections and brain tumors, the nerve may become damaged or destroyed; this will cause the patient to lose the ability to smell and taste. This can also occur if the olfactory bulb or olfactory tract is destroyed. The olfactory tract is composed of many axons that connect the olfactory bulb and other limbic brain regions as well as temporal lobe.