Olfactory and gustatory pathway

Olfactory pathway - 1: Olfactory bulb 2: Mitral cells 3: Bone (Cribriform plate) 4: Nasal epithelium 5: Glomerulus 6: Olfactory receptor cells

Olfactory pathway

The olfactory pathway is a two-neuron uncrossed pathway carrying olfactory information from n. olfactorius.

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  Above yellow bulbus and tractus olfactorius
  1. neuron – neuroepithelial olfactory cell of the epithelium concha nasalis sup. (pars olfactoria cavitatis nasi). Axons (fila olfactoria = nn. olfactorii) exit through the lamina cribrosa ossis ethmoidalis to the bulbus olfactorius (at the base of the frontal lobe) - form the primary olfactory center →
• 2. neuron – mitral cell in the olfactory bulb. The axons continue further along the tractus olfactorius to the trigonum olfactorium. Further, the pathway branches to the gyrus olfactorius medialis and lateralis. It leads without a connection in the thalamus to the temporal cortex (temporal lobe) – uncus gyri parahippocampalis, area entorhinalis (area 28), periamygdalar cortex, prepiriform cortex. It further leads to the corpus amygdaloideum, hypothalamus, hippocampus and through the ncl. mediodorsales thalamus to orbitofrontal cortex (area 11, 12, 47).

Smell is probably the oldest of the five senses, but the latest to be understood. During development, it maintained its connection with parts of the brain that developed into a sorting center for emotional responses, connecting different smells with our feelings.

Smell plays an important role in sexual attraction, although this area has changed considerably during human evolution. At the same time, it functions as a warning system and information collector: it warns us of danger and provides us with valuable information about the outside world. We are not always aware of the connection between taste and smell. Only with a cold do we find that not only our sense of smell is weakened, but also our taste.

Similar to other organs in the body, the olfactory apparatus is duplicated, but each circuit works independently. The sensory receptors for smell are located in the ceiling of the nasal cavity, just below the frontal lobes of the brain. This area is called the olfactory area (area olfactoria), it is densely covered with millions of small olfactory cells. Each olfactory cell has about a dozen fine hairs, cilia, which protrude into the mucus layer. The mucus moistens the cilia and serves as a trap for dusty substances. Cilia increase the surface area of ​​each olfactory cell, increasing our sensitivity to smells.

It is not entirely clear how minute amounts of chemical substances trigger odor perception in olfactory cells. These substances are thought to dissolve in the mucus-like fluid, stick to the cilia and cause the cells to send out electrical signals. The fibers of the olfactory nerve conduct these signals from the skull bones to the two olfactory bulbs (bulbus) in the brain, where the information is collected, processed and then passed through a complex circuit of nerve endings to the cerebral cortex. Here the stimulus is identified and we become aware of the olfactory sensation.

Olfactory nerve

Nervus olfactorius

Nervus olfactorius (1st cranial nerve, olfactory nerve) is referred to as a false cranial nerve, it is a paired set of fibers formed bilaterally by the axons of olfactory cells originating from the pars olfactoria of the nasal mucosa. It arises as an outgrowth of the telencephalon. It has no cores and does not branch.

Course of the olfactory nerve

It is formed by unmyelinated central processes (fila olfactoria) of olfactory cells, which are located in the regio olfactoria of the mucous membrane of the nasal cavity. The dendrites extending from the olfactory cells are spherically expanded at the ends, and several cilia extend from this expansion into the mucus layer on the surface of the mucous membrane. Odor substances soluble in water or in mucus bind to receptors on the surface of the cilia. This causes irritation and nerve impulses are conducted to the olfactory bulb (bulbus olfactorius).

The projections of the olfactory cells form a plexus from which the olfactory nerves emerge. These penetrate the openings in the lamina cribrosa ossis ethmoidalis and sink into the right and left bulbus olfactorius. Inside the bulb, it branches and ends on the dendrites of the mitral cells. Mitral cells serve to conduct olfactory signals through the olfactory pathway to the primary olfactory cortex area (paleocortex, pyriform cortex, entorhinal cortex)

Poruchy čichového nervu

• Hyposmia – partial loss of smell;
• anosmia – complete loss of smell;
• hyperosmia – excessive sensitivity;
• parosmia – qualitative disorder.

More detailed information about olfactory disorders can be found here.

Gustatory pathway

Taste bud

The taste pathway is one of the three-neuron afferent pathways. It conducts specific sensory signals from the taste cells located in the taste buds (caliculi gustatorii) of the tongue, pharynx and palate.

Track breakdown

1. neuron

pseudounipolar cells located in ganglion nervi facialis, glossopharyngeus et vagus (whose dendrites come into contact with taste cells)

2. neuron

cells of nucleus gustatorius (part of ncl. solitarius)

3. neuron

cells ncl. ventralis posteromedialis of the thalamus. From there, its axons go to the insular area and area 43 of the cerebral cortex, which are the terminal areas of the taste pathway

In general, it can be said that the taste pathway transfers five basic taste entities - salty, sweet, bitter, sour and umami (glutamate sensation).

Links

Related articles

• Taste substances
• VIsual pathway
• Auditory pathway
• Nervus olfactorius
• Smell disorders
• Cranial nerves

External links

• {{Cite

| type = web | surname1 = Jančálek | name1 = Radim | surname2 = Dubový | name2 = Petr | url = http://portal.med.muni.cz/clanek-560-zaklady-neuroved-v-zubnim-lekarstvi.html | source_name = Základy neurověd v zubním lékařství | publisher = MEFANET | year = 2011 | revision_date = 27.10.2011 | cited = 26.11.2011

Source

• ČIHÁK, Radomír. Anatomie 3. 2. edition. Grada Publishing, 2004. 692 pp. ISBN 978-80-247-1132-4.

• PETROVICKÝ, Pavel. Anatomie s topografií a klinickými aplikacemi III. -- Neuroanatomie, smyslová ústrojí a kůže. 1. edition. 2002. ISBN 80-8063-048-8.

• GRIM, Miloš – DRUGA, Rastislav. Základy anatomie, Periferní nervový systém, smyslové orgány a kůže. 1. edition. Galén, 2014. 173 pp. ISBN 978-80-7492-156-8.

• Ústav anatomie 3. LF UK. Čichová dráha [online]. [cit. 2010-12-14]. <http://old.lf3.cuni.cz/anatomie/cns_drahacich.htm>.