Olfactory System Flashcards
Describe the path of the Olfactory nervous network from the mucosa cells in the nose and mouth to the cortex.
- Olfactory receptor cells (chemoreceptors) in mucosa
- Project to form olfactory fila
- Pass through ethmoid bone
- Collect into olfactory bulb on the inside on the inferior surface of the frontal lobe
- Projections from bulb form olifactory tract
What type of cells are the olfactory receptor cells?
Chemoreceptors
What are the 2nd order cells found in the olfactory bulb called?
Mitral cells
What is the principal central projection pathway for the olfactory system?
- Lateral olfactory tract
What do the fibers of the lateral olfactory tract project to?
- Primary olfactory cortex (amygdala nad parahippocampal gyrus)
- Amygdala
Where do the fibers not included in the lateral olfactory tract project to?
The anterior olfactory nucleus
What is the path from the olfactory tract to the anterior olfactory nucleus?
Fibers project back through the olfactory tracts to both bulbs, with some fibers crossing in the anterior commisure
Where does the olfactory information from the primary olfactory cortex and amygdala project to?
- Hypothalamus
- Limbic structures
- Thalamus
How is the hypothalamus related to smell?
Connects smell to the autonomic nervous system
What limbic structures receive smell information?
- Hippocampus
- Rest of amygdala
What portion of the neocortex is related to olfaction?
Orbital cortex
What 2 functions related to smell does the Orbital cortex perform?
- Discriminates and identifies food odors
- Perceives taste and flavor
What nucleus of the thalamus does the orbital cortex project to?
Dorsomedial nucleus
Why does smell have an effect on memory?
Orbital cortex projects to hippocampus
What portion of the temporal lobe in the olifactory lobe?
Rostral portion
What is the loss of the ability to smell?
Anosmia
What is distortion of the usual sense of smell?
Parosmia
What is the loss of taste sensation?
Ageusia
What types of deficits typically resut from head injuries or neurodegenerative disease?
Sensorineural olfactory deficits
Why is smell a useful diagnostic tool for tumors growing on the base of the skull?
Tumors growing on the orbital surface of the frontal lobe can become large before affecting any other sensation besides smell
What type of deficits prevent the process of odorants reaching the olfactory epithelium?
Conductive olfactory deficit
What can cause conductive olfactory deficits?
- Nasal polyps
- Septal deviations
- Inflammation
What area of the cortex may be involved in seizures following an unpleasant illusion of smell or taste?
The uncus
What motor phenomena may result from uncinate seizures?
- Smacking of the lips
- Chewing movements
What cognitive changes can occur in uncinate seizures?
- Dreamy states
- Deja vu
What cranial nerves carry taste sensation?
CN VII: Anterior 2/3rds
CN IX: Posterior 1/3rd
What portion of the thalamus receives taste projections?
Ventroposterior medial nucleus
What is the primary taste cortex?
Insula
What is the secondary taste cortex?
Oribtofrontal cortex
What does the ventroposterior medial nucleus project to first? Second?
- S1 to localize taste on tongue
- Insula
Secondary: Orbitofrontal cortex
What 2 structures provide a feeding role to the taste pathways?
Lateral hypothalamus
Amygdala
What other centers can project to the frontal lobe in a similar fashion to smell?
Vision
What nucleus in the brain stem receives taste projections?
The solitary nucleus
How is the OFC related to behavior?
Taste is tied to the reward system
What is unique about the how the olfactory system and the cortex?
Connects directly to the cortex
What types of chemicals is smell intended to detect?
Violatile chemicals
What tissue are the olfactory receptor cells found in?
Olfactory epithelium
