olfactory tract

Examples of olfactory tract in the following topics:

• Olfactory (I) Nerve

  • The olfactory nerve, or cranial nerve I, is the first of the 12 cranial nerves.
  • The specialized olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity.
  • The olfactory nerves consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the cribriform plate of the ethmoid bone.
  • Olfactory receptor neurons continue to emerge throughout life and extend new axons to the olfactory bulb.
  • These interactions are transduced into electrical activity in the olfactory bulb, which then transmits the electrical activity to other parts of the olfactory system and the rest of the central nervous system via the olfactory tract.

• Olfaction: The Nasal Cavity and Smell

  • Olfactory sensitivity is directly proportional to spatial area in the nose—specifically the olfactory epithelium, which is where odorant reception occurs.
  • The area in the nasal cavity near the septum is reserved for the olfactory mucous membrane, where olfactory receptor cells are located.
  • This area is a dime-sized region called the olfactory mucosa.
  • Olfactory transduction is a series of events in which odor molecules are detected by olfactory receptors.
  • The olfactory nerve connects the olfactory system to the central nervous system to allow processing of odor information.

• Tissues and Aging

  • The sense of smell begins to degenerate with the loss of olfactory sensory neurons and loss of cells from the olfactory bulb.
  • This causes more urinary tract infections in the elderly.
  • The prostate gland is often implicated in various disorders of the urinary tract.
  • With the advancing of age, the airways and tissue of the respiratory tract become less elastic and more rigid.
  • Describe the effects of aging on bones, muscles, the nervous and digestive systems, and the respiratory tract

• Taste and Smell at Birth and in Old Age

  • Infants are responsive to the olfactory cues associated with maternal breast odors.
  • Studies demonstrate that the changes to the olfactory bulb and main olfactory system following birth are extremely important and influential for maternal behavior.
  • A diagram of the olfactory system is shown in .
  • Pregnancy and childbirth result in a high state of plasticity of the olfactory system that may facilitate olfactory learning within the mother.
  • Human olfactory system. 1: Olfactory bulb 2: Mitral cells 3: Bone 4: Nasal epithelium 5: Glomerulus (olfaction) 6: Olfactory receptor cells

• Reception and Transduction

  • The olfactory epithelium is a collection of specialized olfactory receptors in the back of the nasal cavity that spans an area about 5 cm2 in humans.
  • An olfactory receptor, which is a dendrite of a specialized neuron, responds when it binds certain molecules inhaled from the environment by sending impulses directly to the olfactory bulb of the brain.
  • Olfactory neurons are bipolar neurons (neurons with two processes from the cell body).
  • Each olfactory sensory neuron has only one type of receptor on its cilia.
  • In the human olfactory system, (a) bipolar olfactory neurons extend from (b) the olfactory epithelium, where olfactory receptors are located, to the olfactory bulb.

• Thalamus

  • The thalamus is connected to the hippocampus via the mammillothalamic tract.
  • In particular, every sensory system (with the exception of the olfactory system) has a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area.

• Sensory and Motor Tracts

  • The spinothalamic tract is a somatosensory tract and the corticospinal tract is a motor tract.
  • The spinothalamic tract is a sensory pathway originating in the spinal cord.
  • The types of sensory information transmitted via the spinothalamic tract are described as affective sensation.
  • The corticospinal tract conducts impulses from the brain to the spinal cord.
  • The corticospinal tract is made up of two separate tracts in the spinal cord: the lateral corticospinal tract and the anterior corticospinal tract.

• Organization of Motor Neuron Pathways

  • These are the upper motor neurons of the corticospinal tract.
  • They then descend as the lateral corticospinal tract.
  • These are the rubrospinal tract, the vestibulospinal tract, the tectospinal tract, and the reticulospinal tract.
  • The function of lower motor neurons can be divided into two different groups: the lateral corticospinal tract and the anterior corticalspinal tract.
  • Included in the diagram are the following motor pathways: corticospinal tracts (pyramidal tract), and extrapyramidal tracts (tectospinal tract not delineated).

• Somatic Sensory Pathways to the Cerebellum

  • Both tracts involve two neurons.
  • The dorsal spinocerebellar tract does not decussate, or cross sides, at all through its path.
  • This is one of the few afferent tracts through the superior cerebellar peduncle.
  • The dorsal spinocerebellar tract (also called the posterior spinocerebellar tract, Flechsig's fasciculus, or Flechsig's tract) conveys inconscient proprioceptive information from the body to the cerebellum.
  • This tract involves two neurons and ends up on the same side of the body.

• Amoebic Meningoencephalitis

  • However, thus far the only route for Naegleria fowleri to enter the central nervous system is via deep insufflation of infected water as it attaches itself to the olfactory nerve, which is exposed only at the extreme vertical terminus of the paranasal sinuses.
  • When this occurs, it then migrates through the cribiform plate and into the olfactory bulbs of the forebrain, where it multiplies itself greatly by feeding on nerve tissue.
  • During this stage, occurring approximately 3–7 days post-infection, the typical symptoms are parosmia, rapidly progressing to anosmia (with resultant ageusia) as the nerve cells of the olfactory bulbs are consumed and replaced with necrotic lesions.
  • After the organisms have multiplied and largely consumed the olfactory bulbs, the infection rapidly spreads through the mitral cell axons to the rest of the cerebrum, resulting in onset of frank encephalitic symptoms, including cephalgia (headache), nausea, and rigidity of the neck muscles, progressing to vomiting, delirium, seizures, and eventually irreversible coma.
  • The parasite also demonstrates a particularly rapid late-stage propagation through the nerves of the olfactory system to many parts of the brain simultaneously (including the vulnerable medulla).