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2. Olfaction

3. Learning object Introduction Site of action Olfactory pathways Unique features Disorder of olfaction

4. Introduction Action or capacity of smelling is called olfaction. Sense of smell are very well developed in animals like dog and rabbit. Are due to stimulation of olfactory receptor. Arises due to to irritation property of their vapours which stimulate with to cranial nerve. Even over stimulation of same chemical causes pain.

5. Site of olfaction Olfactory mucosa Vomeronasal organ A-Olfactory mucosa Includes roof of nasal cavity It conist of 3types of cell ▪Receptor cell- sensory neuron whose cell body are close to external environment. have short life spanabout 60 days(pbc) ▪Supporting ceĺl- secrete mucus ▪Basal cell- from which new cells are formed Nerve spupply- Special sensory- first cranial nerve General sensory- branch of fifth cranial nerve(trigeminal) B- Vomeronasal organ These are not well develop in human beings It is cocerned witn eating behaviour and reproduction.

7. Olfactory pathways- Comprises Olfactory nerve- bipolar neuron pierces to cribriform palate to reach olfactory bulb Olfactory bulb- contains mitral cell, tufted cell, periglomerular cell Olfactory tract - neurons recieve synaptic connections from olfactory bulb which excite inhibitory contralateral olfactory bulb. Olfactory cortex- includes anterior olfactory nucleus,prepiriform cortex, olfactory tubercle,and amygdala(parts if limbic system)

8. Unique features Directly project to orbitofrontal cortex Receptor neuron directly contact to environment Olfactors are also called telereceptor, chemoreceptor which adopt with in seconds - minutes.

9. Disorders Anosmia-inability to smell Hyposmia- diminished olfactory sensitivity hypersomia- enhanced olfactory sensem(pregnant)

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