Flashcards in Chemosensation Deck (15):
In a subset of people, loss of smell is a symptom of _____________.
Loss of taste is called _____________. Loss of smell is _________.
Which is more common, loss of taste or smell?
Which cranial nerves innervate the tongue?
Anterior 2/3: facial (VII)
Posterior 1/3: glossopharyngeal (IX)
Larynx: vagus (X)
There are five tastes that we can sense. List them and give the type of channel that mediates their signals.
Describe the mechanism of the GPCR receptors.
Upon binding a ligand, the beta-gamma unite activates phospholipase which activates IP3; this releases sarcoplasmic calcium that opens sodium channels (TrpM5) and leads to depolarization.
The gustatory neurons first synapse on ____________.
the solitary nucleus (upper-mid medulla), which projects axons to the VPM in the thalamus
After a ligand binds to an olfactory receptor, what happens?
A GPCR second-messenger cascade (starting with G-alpha) leads to an increase in cAMP; the increased cAMP binds to calcium channels, allowing in a small amount of calcium. Calcium bind to chloride channels and the outflow of chloride depolarizes the cell.
The olfactory tracts lead to what gyri?
The piriform gyri of the medial temporal lobes and thence to the orbitofrontal (conscious smell)
The entorhinal cortex of the hippocampus (memory)
Amygdala/hypothalamus (visceral reaction)
Strong chemical smells and spices activate the ________ nerve.
The pheromone-sensing organ present in many animals is called the _____________.
What are the three kinds of chemosensory cells in the body?
Olfactory: bipolar neurons
Gustatory: modified epithelium that synapses on ganglion cells
Chemesthesis: free nerve ending of trigeminal ganglion
List the three types of papillae and their locations.
Fungiform: anterior top
Like the photoreceptors, taste cells also _____________.
fire in response to multiple sensations (integrating them to avoid hypersensitivity)