Taste and Smell: Chemoreception - Anatomy and Physiology
- Which substance does the umami taste mainly detect?
- Glutamate (an amino acid), giving a savory taste.
- Which cranial nerve carries taste from the anterior two-thirds of the tongue?
- The facial nerve (CN VII), via the chorda tympani. The posterior third is served by the glossopharyngeal nerve (CN IX).
- Which tongue papillae lack taste buds?
- Filiform papillae. Fungiform, foliate and vallate papillae contain taste buds.
- Why must an odorant dissolve in nasal mucus before it can be smelled?
- Odorants must reach and bind receptor proteins on the cilia of olfactory neurons, which lie within the mucus layer.
- How does the olfactory pathway differ from other sensory pathways in reaching the cortex?
- It reaches the olfactory cortex and limbic areas without first relaying in the thalamus.
- What are the five basic taste qualities?
- Sweet, sour, salty, bitter, and umami.
- Which taste qualities are detected through G protein-coupled receptors?
- Sweet, bitter and umami. Salty and sour are detected mainly through ion channels (Na+ and H+).
- What type of cell are olfactory receptor cells, and how are they unusual?
- Bipolar neurons in the olfactory epithelium that are continually replaced from basal stem cells.
- A skull fracture damages the cribriform plate of the ethmoid bone. Which sense is most likely lost?
- Smell (anosmia), because olfactory nerve axons pass through the cribriform plate to the olfactory bulb.
- How do olfactory receptors transduce odorant binding into a signal?
- They are G protein-coupled receptors that raise cAMP, opening cation channels and depolarizing the neuron.
- Where is the primary gustatory cortex located?
- In the insula (with the adjacent frontal operculum).