ORNs and Glomeruli Selectivity in Odor Perception

Play an AI-generated podcast conversation about this lesson

What is the enzyme activated by Golf that leads to the generation of cyclic AMP?

Adenylate cyclase (ACIII)

What is the name of the G-protein activated by the association of an odorant with its receptor?

Golf

What ions are permitted to influx into the cilia when the cation-selective channel is open?

Na+ and Ca2+

What is the main molecule responsible for depolarization of the olfactory receptor potential?

Ca2+ Signup and view all the answers

How is the receptor potential reduced in magnitude in the olfactory signal transduction cascade?

By breaking down cAMP using specific phosphodiesterases Signup and view all the answers

What happens to the affinity of the channel for cAMP when Ca2+ complexes with calmodulin (Ca2+-CAM)?

Reduces Signup and view all the answers

What is the threshold concentration for quinine?

0.008 mM Signup and view all the answers

What is the threshold concentration for strychnine?

0.0001 mM Signup and view all the answers

Where are taste papillae located?

On the full surface of the tongue Signup and view all the answers

What is the structure of taste buds?

Specialized neuroepithelial receptor cells called taste cells, supporting cells, and occasional basal cells Signup and view all the answers

How many taste buds are distributed in humans?

Approximately 4000 taste buds Signup and view all the answers

How do individual glomeruli respond to distinct odorants?

Individual glomeruli respond specifically (or selectively) to distinct odorants. Signup and view all the answers

What is the structure of circumvallate papillae?

Circular trench containing about 250 taste buds along the trench walls Signup and view all the answers

What physiological techniques have been used to confirm the selective responses of subsets of glomeruli to particular odorants?

Single and multiunit recordings, metabolic mapping, voltage-sensitive dyes, genetically encoded sensors of electrical activity, or intrinsic signals that depend on blood oxygenation have been used. Signup and view all the answers

What effect does increasing the odorant concentration have on individual glomeruli?

Increasing the odorant concentration increases the activity of individual glomeruli. Signup and view all the answers

How do different single odorants or odorants with distinct chemical structures activate glomeruli?

Different single odorants or odorants with distinct chemical structures maximally activate one or a few glomeruli. Signup and view all the answers

Why might one expect complex natural odors like coffee, fruits, cheeses, or spices to activate a large number of olfactory glomeruli?

One might expect this due to the complex composition of these natural odors, each of which is composed of more than 100 compounds. Signup and view all the answers

What is still unclear regarding the mapping of odor identity and concentration across the entire array?

It is still not clear how (or whether) odor identity and concentration are mapped across the entire array, or reflect the activation of smaller subsets of glomeruli. Signup and view all the answers

What is the main function of taste cells?

To transduce chemical stimuli to encode information about the identity, concentration, and qualities of the substance. Signup and view all the answers

How does taste information prepare the gastrointestinal system?

By causing salivation, swallowing, gagging, or regurgitation depending on the quality of the substance. Signup and view all the answers

Where are taste cells (peripheral receptors) found?

In taste buds distributed on the dorsal surface of the tongue, soft palate, pharynx, and upper part of the esophagus. Signup and view all the answers

How is information about temperature and texture of food relayed from the tongue and mouth?

Via somatosensory receptors from the trigeminal and other sensory cranial nerves to the thalamus and somatosensory cortices. Signup and view all the answers

Apart from nutritional value, what other factors influence taste preferences?

Cultural and psychological factors. Signup and view all the answers

How is the taste system similar to the olfactory system?

Both are defined by specialized peripheral receptors and central pathways that relay and process sensory information. Signup and view all the answers

What is the ultimate solution to the vulnerability of ORNs?

Maintain a healthy population by a normal cycle of degeneration and regeneration. Signup and view all the answers

What type of stem cells are responsible for ORN regeneration?

Neural stem cells among the basal cells in the mature olfactory epithelium. Signup and view all the answers

In what other exposed epithelia is a similar cycle of degeneration and regeneration found?

Intestine and lung. Signup and view all the answers

How often are most olfactory neurons renewed in rodents?

Every 6 to 8 weeks. Signup and view all the answers

What are some of the harmful substances that ORNs are exposed to?

Airborne pollutants, allergens, microorganisms, and other potentially harmful substances. Signup and view all the answers

What is the role of basal cells in the olfactory epithelium?

They give rise to new receptor neurons. Signup and view all the answers