Somato - CN 2 Flashcards
External anatomy on nose
Nose pad or rhinarium
Alar fold
External nares
Philtrum
Internal nasal anatomy
Nasal cavity
- Cribriform plate
- olfactory bulb
- brain
- spinal cord
Oral cavity
- pharynx
- epiglottis
- esophagus, trachea, larynx
Olfactory epithelium of nasal cavity
Specialized tissue to receive cells
Goblet cells & cilia
Olfactory epithelium
Support cells - cilia
Stem cells for regeneration
Receptor cells - bipolar neurons* = receptive field on one side and info center in the middle
Function of olfactory epithelium
G protein couples receptors
Odorant binds to odor receptor, activates G protein, cAMP = indirect channel opening
Primary receptor
Odorant receptor genes
800+ olfactory receptor genes
600+ olfactory receptors
1000+ odorants
Olfactory pathways
Pathways are not ipsilateral
DOES NOT project to thalamus en route to cortex
Olfactory bulb —>
Frontal cortex - conscious perception of smell
Hypothalamus amygdala - motivational/emotional aspect
Hippocampus - odor memory
Sniffing
Contracts alar folds so air comes in external nares and exits the alar folds
Air flow
Into olfactory complex
Down trachea to lungs
Lateral action
Dogs prefer to sniff w right nostril
Will switch to left if smell is familiar or non threatening
Will continue with right if smell is new or threatening
Left brain & smells
Signals from left nostril go to left side of brain, linked more to parasympathetic system
Right brain and smell
Signals from right brain go to the right side of the brain & is linked to sympathetic system
Skulls for sniffing
Dolichocephalic - CI < 50
Mesocephalic - 50< Cl < 60
Brachycephalic - 60<Cl
Factors that decreased olfactory acuity in dogs
High temp
High humidity
Intense exercise
Dehydration
Age (>14 years)
Diet high in saturated fats
Medications
Viral infections
Nasal tumors
Encephalitis /brain tumors
