Olfactory system and functioning in human
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The document discusses the olfactory system, which is responsible for the sense of smell, detailing the pathways for odor detection and the anatomy of olfactory receptor cells. It describes the types of cells involved, their functions, and the neural pathways leading to the olfactory bulbs. Additionally, it addresses the causes and treatments for loss of smell, including conditions like infections and aging.
Olfactory system and functioning in human
- 2. Responsible for sense of smell. This sense, also known as olfaction, involves in the detection and identification of molecules in the air. Once these senses are detected by sensory organs, nerve signals are sent to the brain where the signals are processed.
- 3. ORTHONASAL PATHWAY:- odors that enter the nasal passages and are detected by chemical receptors in the nose. RETRONASAL PATHWAY:- connects the top of the throat to the nasal cavity and involves aromas that are contained within the foods we eat.
- 4. Consists of three cell types:- Basal cell Supporting cell Olfactory receptor cell
- 5. BASAL CELL:- Stem cells that give rise to the olfactory receptor cells. Continuous turnover unique to the olfactory system. SUPPORTING CELL:- Scattered among the receptor cells and have numerous microvilli and secretory granules, which empty their contents onto the mucosal surface. OLFACTORY RECEPTOR CELL:- Bipolar neurons, each possessing a thin dendritic rod that contains specialized cilia. The cilia provide the transduction surface for odorous stimuli.
- 6. Each neuron has thick dendrite with an expanded end called an olfactory rod. From rods, cilia project to surface of mucus. Each receptor neuron has 10-20 cilia. Axon of the olfactory receptor neurons pierce the cribriform plate of ethmoid bone and enter the olfactory bulbs. Live for 5-8 weeks and then die.
- 7. Olfactory mucus membrane is constantly covered by mucus. Mucus is produced by Bowman’s glands, which are just under the basal lamina of the membrane.
- 8. Axon of receptors contact the primary dendrites of the mitral cells and tufted cells. Forming complex globular synapse called olfactory glomeruli. Tufted cells are smaller then mitral cells and have thinner axons, but both types send axons into the olfactory cortex.
- 9. Also contain Periglomerular cells, which are inhibitory neurons connecting one glomerulus to another. Granule cells, which have no axon and make reciprocal synapse with the lateral dendrites of mitral and tufted cells. At these synapses, mitral and tufted cell excites the granule cells by releasing glutamine, and granule cells in turn inhibits both by releasing GABA.
- 11. Odor memoryMotivational and emotional aspects of smell Conscious perception of smell
- 12. Loss of sense of smell. Temporarily or permanently. May be to specific odors or all odors. Major Caused:- by infection to nasal cavity or brain injury (frontal).
- 13. Common cold Normal aging Hay fever due to allergy Influenza Sinus infection
- 14. Loss of smell TREATMENT:- Can not be treated if caused by brain damage. If caused by inflammation changes in mucosa, it can be treated by glucocorticoid.