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30 Cards in this Set

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Four groups of Olfactory Disturbances
1. Quantitative abnormalities
2. Qualitative abnormalities
3. Olfactory Hallucinations/delusions
4. Higher-Order loss of discrimination
1. Quantitative Olfactory Abnormalities
a. Anosmia (or hyposmia)
b. hyperosmia
2. Qualitative Olfactory Abnormalities
a. dysosmia (or parosmia)
3. Olfactory Halllucinations/delusions
a. uncinate fits
4. Higher order loss of Olfactory discrimination
a. Olfactory agnosia
Anosmia (or hyposmia)
Loss or reduction of sense of smell
- can be at the nasal, neuroepithelial, or central level
- if bilateral, pt usually complains of ageusia (loss of taste)
Hyperosmia
Increased olfactory acuity
- very rare
Dysosmia (or parosmia)
Distortions or illusions of smell
- may be assoc with depressive illness
Uncinate fits
Olfactory hallucinations associated with temporal lobe seizures
- always of central origin
Olfactory Agnosia
Perceptual aspects intact, but can't recognize the smell
What is the Olfactory Epithelium?
receptor surface for olfaction and is located in the nasal cavity (peripheral beginning of olfactory system)
What is the Olfactory tract?
Formed by the axons of the olfactory receptor cells
Where do the axons of the olfactory receptor cells synapse?
The Olfactory Bulb
After the olfactory bulb, what is the next connection of the olfactory system?
The Pyriform cortex
From the pyriform cortex, the primary projection goes to:
Dorsal medial thalamic nucleus
The Dorsal medial thalamic nucleus projects where?
The Orbital frontal cortex
The second projection from the pyriform cortex goes to:
Lateral hypothalamus
The lateral hypothalamus projects where?
The Orbital frontal cortex
What is the primary olfactory neocortex?
The orbital frontal cortex
What are the two parallel routes for olfactory input to the cortex?
1. Dorsal medial thalamus
2. Lateral hypothalamus
What are the majory connections of the olfactory system?
1. Olfactory Bulb
2. Pyriform cortex
3/4. Dorsal medial thalamus/Lateral hypothalamus (parallel routes)
5. Orbital frontal cortex
Olfactory receptor neurons
1. Are true neurons
2. A single dendrite and a single axon
3. Axon is unmyelinated, resulting in slow conduction
What is the Olfactory filia?
Collection of olfactory receptor neurons which make up the first cranial nerve
What is unique about the sense of smell?
It does not involve a direct relay from the thalamus (although the thalamus is part of subsequent olfactory circuitry)
Are olfactory receptor neurons represented in the contralateral or ipsilatera cerebral hemisphere?
Ipsilateral
What are the two general kinds of processes that can disrupt the sense of smell?
1. Conductive olfactory deficit
2. Sensorineural olfactory deficit
What happens in a conductive olfactory deficit?
A process prevents odorants from reaching the olfactory epithelium
What happens in a sensorineural olfactory deficit?
A process damages olfactory receptor neurons or parts of the olfactory CNS
What can cause conductive olfactory deficits?
Nasal polyps
Septal deviations
Inflammations
What can cause sensorineural olfactory deficits?
Head Injuries
Neurodegenerative disorders (Parkinson's and Alzheimer's)