THE OLFACTORY BULB AND ITS POSTURAL CORRELATIONS

The nerve and the olfactory bulb are receptors connected to multiple functions of our body and we often limit ourselves to considering only the sensory function of smell.

In addition to this, the olfactory nerve is also the first nerve receptor of respiration, having the function of reading the amount of oxygen we inhale, but it is also closely linked to the sexual function of the brain. During this chapter we will try to understand the correlations of this nerve.

The nasal cavities

The nose is the epicenter, the engine, or rather the control unit for proper breathing. Its structure is subject to repeated trauma already during pregnancy, and more precisely during childbirth, when there can be a strong compression of the bones of the face and more so in prolonged labors; when the bones of the face are compressed during the rotational movement that the newborn performs when entering the pelvis during delivery.

During life, the face is just as easily subject to trauma.

These traumas will limit the movement related to the bones of the face and therefore also the respiratory function.

The nasal cavities are cramped and narrowed in their extension from front to back. The valvular (inlet) area is the one that offers about 60% of the resistances, the turbinates, when they are hypertrophied, oppose the passage of air and the nasopharynx also has an opposition role determined by its 90° curvature: therefore this alters and diverts the air flow.

These anatomical peculiarities are not accidental, but functional to perform the functions of: heating, humidifying and filtering the inhaled air.

The nose therefore functions as a highly evolved air conditioner. Breathing through the nose allows the brain to cool down, as is the case with the radiator of the car. The passage of air in the nose, through its narrow areas, causes accelerations and vortices for the filtering of impurities that remain adhered to the nasal mucosa.

The turbinates, especially the lower ones, heat the air, which also receives water vapor and body heat from the latter, richly vascularized, so as to make it reach the lungs at a temperature of 37°C, with optimal humidity and free from pollutants.

The nasal control unit is also the one that determines the amount of air that will reach the lungs; In a nutshell, it regulates the airflow that passes through the nose. The faulty nasal control unit prevents the boiler (the bronchi) from working.

According to Christina Zelano, assistant professor of neurology at Northwestern University Feinberg School of Medicine, “there is a dramatic difference in brain activity in the amygdala and hippocampus during inhalation versus exhalation. When you inhale, we found that you stimulate neurons in the olfactory cortex, amygdala, hippocampus, and throughout the limbic system,” which also activates functions other than respiratory and olfactory functions.

The olfactory nerve

The olfactory nerve is the first receptor of the nasal cavity and is part of the first pair of cranial nerves and is exclusively of the sensory type. Its real origin is at the level of the olfactory cells of the mucous membrane of the nasal cavities. Its fibers are then collected in bundles that are divided into two groups: a medial and a lateral one. The medial one comes from the olfactory mucosa that lines the nasal septum; the lateral one from the mucosa of the upper nasal horn. They both cross the cribrous lamina of the ethmoid bone to reach the olfactory bulb welcomed in the homonymous shower of the brain.

Its function is to receive the olfactory stimuli that reach the nasal cavities and transport them to the brain in the form of electrical impulses.

Attached to the olfactory nerve is the terminal nerve, whose function is still uncertain, it is not involved in olfactory sensitivity and several ganglion cells are disseminated along its course. It probably has functions that regulate other physiologies in our body.

The odors enter the nasal cavity through the nostrils, reach the olfactory epithelium, a thin layer of cells located in a narrow area of the nasal cavity, between the upper part of the middle nasal horn, the entire upper nasal horn and the vault in the lateral wall, while on the medial wall it is present in the upper portion of the nasal septum below the lamina cribrosa.

An olfactory cell is a bipolar neuron with an elongated soma with the apical surface (directed towards the nasal cavity) consisting of a long dendrite that ends with an olfactory node, from which numerous cilia branch off immersed in the nasal mucus that acts as a means of capturing and diffusing odorants.

Each olfactory neuron is separated from the adjacent one by support cells. The information is projected directly through its axons to the olfactory bulb, a nerve structure located just above the cribrous lamina of the ethmoid that continues posteriorly with the olfactory tract. The axons enter the olfactory bulb by aggregating into small bundles covered with supporting olfactory cells, which penetrate through the holes of the lamina cribrosa, forming the olfactory nerve, the first cranial nerve. In the olfactory bulb, the axons of the olfactory cells have connections with the dendrites of the mitral cells or with those of the plume cells (second-order neurons), forming structures called glomeruli. The axons of mitral cells and plume cells travel along the olfactory tract in the anterior cranial fossa, some synaptan at the anterior olfactory nucleus and then continue along the olfactory tract to the nucleus of the lateral olfactory tract or the medial olfactory stria, and then project to the anterior commissure.

Other axons of the olfactory tract synapt at the olfactory tubercle and then move to the piriformis lobe (part of the temporal lobe), the anterior perforated substance, the hypothalamus, the uncus, the amygdala and the entorhinal cortex (Brodmann’s area 28 – 34) through a complex system of neural pathways whose organization and functioning is still more obscure than other sensory systems. Of all the sensory systems, the sense of smell is the only one that does not have pathways coming directly from the primary receptors that project to the thalamus before reaching a specific portion of the neocortex. The piriform cortex, also referred to as the piriform lobe, is also part of the archicortex and has three layers unlike the six layers of the neocortex. Its widespread links to archaeocortex suggest that the sense of smell was one of the first to have developed in living things. The piriformis cortex has axons that project to the thalamus and then from there to associative areas of the orbitofrontal neocortex responsible for the conscious perception of pain. The entorhinal cortex projects to the hippocampal formations, the amygdala to the thalamus and hypothalamus, which are responsible for the emotional perception of smell. It is unclear whether regions such as the olfactory bulb or the piriformis cortex have somatotopic organization in relation to specific odorants or their general characteristics.

The Sexual Sense of Smell

Humans have a second nasal organ, distinct from the main olfactory epithelium, which is called the vomeronasal organ. The job of this organ is to detect certain chemicals such as pheromones, which are capable of influencing an individual’s sexual, reproductive, and social reactions.

Often these substances are released by females of a particular species and end up activating, as in the case of mice, an almost innate response by males. Research has shown that neurons in the vomeronasal system send their impulses to an area of the brain (controlling emotional responses and innate behaviors) that is different from the one receiving signals from the olfactory epithelium (olfactory cortex).

The primary olfactory cortex projects to several other parts of the telencephalon, including the amygdala, hippocampus, hypothalamus, dorsal thalamus, and neocortex. The fibers directed to the hippocampus and amygdala originate mainly from the periamygdaloid cortex and the adjacent rostral olfactory part of the entorhinal cortex.

The limbic system

The limbic system is a portion of the diencephalon, it is made up of a series of brain structures and a set of neuronal circuits present in the deepest and oldest part of the telencephalon, connected to the limbic lobe and related to the fundamental functions for the conservation of the species.

This system is preserved in phylogeny, but not in function, being in fact involved in the integration of smell, short-term memory and in functions that become more complex as one goes up the phylogenetic scale such as emotions, mood and the sense of self-awareness that determine the behavior of the individual. The limbic system also performs functions such as the integration between the vegetative and neuroendocrine nervous systems.

In humans, the limbic lobe consists of the hippocampus, the amygdala, the anterior thalamic nuclei, and the limbic cortex, which support various psychic functions such as emotionality, behavior, short-term memory, and smell.

In the field of smell, it should be remembered that the limbic system shares with the rhinencephalon numerous structures (primary olfactory cortex, amygdala nuclear complex and ventral neostriatum), which therefore give a strong interconnection between these two portions of the brain. In humans, however, the olfactory afferents to the limbic system are very marginal, as those from the associative areas of the cerebral cortex are greater, and this makes the rhinencephalon and limbic system two separable formations with different functions.

For what reasons the olfactory nerve and the olfactory bulb should be treated osteopathically.

Since we are dealing with the first cranial nerve, I would like to clarify a fundamental concept applicable to all nerves: nerve dysfunctions are often determined by tissue compressions along its path. Very often in chronic cases of tissue compression of the nerve, the correction of the structures and soft tissues does not allow the nerve to return to its ideal physiology and continues to inform on a sensory or sensory level, depending on its characteristics. For this reason, the nerves themselves must also be treated, as if they remained in their dysfunction, not to mention pathology, they would continue to computerize the system they innervated incorrectly and to maintain the dysfunctions of the tissues they innervated.

The sensory aspect of the olfactory nerves is important to treat in sensory problems of smell, but also in all pathologies of the airways and for pulmonary problems, associated with structural work of the bones of the face and the treatment of the air sinuses.

The most common problems are: rhinitis, pollen allergies and sinusitis.

The terminal and/or olfactory nerve function as a receptor of the respiratory system; Breathing is one of the vital functions of our body and the body tries to compensate in order to function at its best. In the defect, the whole system compensates and contracts to be able to inhale the greatest amount of oxygen. As previously mentioned, the bones of the face, if dysfunctional, limit the entry of air, the first compensation is immediately located in the nasal cavity where the turbinates contract to suck more area and over time they become hypertrophied, further below the scalene muscles, also called inspiratory accessories, adapt by contracting, and we know that between the anterior and middle bundles passes the brachial plexus and the subclavian artery. This phenomenon is more noticeable when lying down and especially in winter due to heating.

The pleural dome will be fixed and it will also be easy to find a dysfunction at the level of the first rib in inspiration and relative vertebra due to fascial correlations. All the tissues of the rib cage will go into dysfunction: pleura, lungs and bronchi. It can be assumed that the patient has had pathologies on the lower airways, so it is possible that it will be primary to clear cranial dysfunctions and visceral dysfunctions.

By recovering what John Martin Littlejohn left us, we can understand the importance of this dysfunctional circuit (or pathway): “the lungs are excretory organs and if the patient does not lead an outdoor life by combining aerobic movement, pulmonary dysfunctions will create problems for the venous and lymphatic return of the abdomen.”

Let’s go back to the adaptations of the soft tissues, which are established by the difficulty in breathing through the nose: the olfactory nerve and the olfactory bulb will require tissue tensions even at a distance.

The scalenes are the first muscles that behave concentrically and will tend to compress the subclavian artery and the brachial plexus The pleural dome will be painful and high, involving the first rib and also the first thoracic vertebra. If the visceral tissues of respiration are involved, the pleura will not be able to descend and the area of pleural recess, which involves the last ribs, will lose mobility, the drainage of the lungs will also be involved, the lungs and especially the bronchi will go into dysfunction.

Moving on to the abdominal cavity, the diaphragmatic hemidome will have difficulty descending, the psoas, which is closely connected to another excretory organ, the kidney, and also the quadriceps will adapt to the problem of breathing by contracting concentrically. For the diaphragm, psoas and quadriceps there may be other causes that create a concentric contraction of these muscles, activating their trigger points. The kneecap will go into compression. Descending, the intraosseous membrane and plantar fascia will be involved.

Thousands of years ago, yoga had already understood the motor compensations in relation to inhalation.

This dysfunctional pathway is probably established because the difficulty in breathing through the nose will require the soft tissues at a distance to have a greater tissue tension of adaptation.

If the quadriceps contracts, the kneecap will more easily go into compression, possibly causing knee pain.

In short, we went from a respiratory problem to an apparently orthopedic problem.

The olfactory nerve also comes into play in the swallowing mechanism.

The tongue pushes on the palatine folds and then on the anterior 2/3 of the palate, swallowing is performed 2 times a minute during the day and once a minute during sleep and is an activity that involves several cranial nerves.

The nerves that regulate motor activity are: the hypoglossal, the facial, the trigeminal, the glossopharyngeal and the vagus. This thrust on the palate, which is essential for many activities of our body: breathing, balance, kinetic thrust of craniosacral movement, is recorded by the first cranial nerve.

To understand the mechanism, we must take into account that: the olfactory nerve is the first sensory receptor of what happens mechanically inside the mouth, i.e. the thrust of the tongue on the palate.

The tongue is in continuity with the visceral support tissues, i.e. the internal fascial chains

The meningeal chain (craniosacral) and the internal fascial chains (visceral) meet in the buccal cavity and pelvic floor.

A good balance between them is crucial for our health.

So a swallowing dysfunction, which is not only perturbed by neurological factors, but also by ascending fascial-type factors, will alter breathing, and the olfactory nerve will receive this information.

A dysfunctional swallowing will be established that pushes only on the palatine folds and not on the front of the palate and not allowing you to breathe sufficiently, will create compensations on the respiratory system as previously described.

In the case of atypical swallowing, they must be corrected by also associating orthodontic correction of the openbite.

Finally, let’s talk again about the vomero-nasal organ, a structure closely linked to the limbic and neuroendocrine systems, as we previously dealt with the sexual sense of smell.

The physiology of the reproductive system is closely regulated by the neuroendocrine system and the limbic system, which regulates its physiology and mobility.

A loss of mobility and motility of the uterus and prostate is very often a central problem and the vomero-nasal organ is also part of it.

If there are dysfunctions of mobility and motility of the organs of the reproductive system, their congestion and fluid stasis will increase, consequently the pelvic floor and the anterior superficial fascial chain, which inserts itself on the pubis, will have to adapt and lose mobility. The adductor fascia, which is part of the anterior superficial fascial chain, will be the direct victim and will disrupt the physiology of the small saphenous nerve, classic nocturnal pain of the medial compartment of the knee.

There may also be other correlations regarding the olfactory sensory and limbic system, determined by the memory of fears associated with olfactory emotions, the amygdala and hippocampus retain this memory.

This will have repercussions on the organs related to fear, such as kidney and bladder, as Chinese medicine advises.

The locomotor structure that will be affected is the psoas, which is the kidney rail, ipsilateral to the amygdala and hippocampus.

This will result in an overload of the weight on the side of the psoas and also a shift of the pelvis.