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