Set #7 (Lecture 16 + Textbook PGs 181-189 Study Guide)

Why are taste and smell called chemical senses?

Both senses detect chemicals.

What type of chemicals does taste detect?

Chemicals dissolved in saliva.

What type of chemicals does smell detect?

Chemical molecules in the air.

Why is separating taste from smell difficult in fish?

Chemicals for both senses are dissolved in water.

How do scientists distinguish taste from smell in fish?

By which cranial nerve carries the information.

Which cranial nerve carries smell information?

Cranial nerve 1.

Where does smell information enter the brain?

The rostral part of the brain.

Which major brain division initially receives smell information?

The telencephalon.

Which cranial nerves carry taste information?

Cranial nerves 7, 9, and 10.

Where do cranial nerves 7, 9, and 10 enter compared with cranial nerve 1?

Farther back in the brain.

How are cranial nerves numbered based on brain entry?

From more rostral to more posterior entry points.

How is sensory information through cranial nerve 1 classified in fish?

As smell.

How is sensory information through cranial nerves 7, 9, and 10 classified in fish?

As taste.

What is wrong with the traditional tongue taste map?

Separate tongue regions are not limited to specific tastes.

Where can the five basic tastes be detected on the tongue?

Across all areas of the tongue.

Can some tongue regions contain more receptors for particular tastes?

Yes, receptor concentrations can vary.

Where are taste receptors found besides the tongue?

The roof of the mouth, back of the throat, and upper esophagus.

What are papillae?

Tongue structures that contain taste buds.

How many basic types of papillae were described in lecture?

Three.

What do some papillae look like?

Small mushroom-shaped bumps.

About how many taste buds can fungiform papillae contain according to lecture?

About 1-5.

How many taste buds can other papillae contain?

Hundreds.

Where are taste cells located?

Inside taste buds.

What object did the professor compare a taste bud with?

A garlic clove.

About how many taste cells are found in an average taste bud?

About 100.

What is the taste pore?

The small opening at the top of a taste bud.

What reaches taste cells through the taste pore?

Chemicals dissolved in saliva.

What are microvilli in the taste system?

Small extensions from taste cells into the taste pore.

What do taste-cell microvilli help detect?

Chemicals entering the taste pore.

What do taste cells contact at their lower ends?

Gustatory sensory neurons.

Are taste cells neurons?

No, taste cells are receptor cells.

What neuron-like abilities do taste cells have?

Taste cells can become electrically active and release neurotransmitters.

What do supporting cells do in a taste bud?

Support taste cells similarly to glial cells.

What are basal cells in taste buds?

Stem cells that produce replacement cells.

Why are basal cells important for taste?

Taste cells are continually regenerated.

About how often does lecture say taste cells are replaced?

About every 10 days.

What happens first when a chemical produces taste?

The chemical dissolves in saliva and enters a taste pore.

What happens after a chemical reaches taste-cell microvilli?

The chemical activates a taste cell.

How does an activated taste cell pass information toward the nervous system?

The taste cell communicates with a gustatory sensory neuron.

Where do gustatory sensory-neuron axons travel before joining cranial nerves?

Through sensory ganglia.

How many sensory ganglia were described in the taste pathway?

Three.

Which cranial nerves carry information from the taste sensory ganglia?

Cranial nerves 7, 9, and 10.

Where do taste-related cranial nerves enter the brain?

The medulla.

Which brainstem nucleus receives taste information?

The nucleus of the solitary tract.

Where does primate taste information travel after the nucleus of the solitary tract?

The thalamus.

Where does taste information travel after the thalamus?

The gustatory cortex.

What is the primary taste pathway?

Taste cells, sensory neurons, sensory ganglia, cranial nerves 7/9/10, medulla, solitary tract nucleus, thalamus, gustatory cortex.

Where is the gustatory cortex located according to lecture?

The parietal lobe.

What cortical representation is located near the gustatory cortex?

The face area of the somatosensory cortex.

Does taste processing stop at the gustatory cortex?

No, additional processing occurs in other brain areas.

What are the five basic tastes?

Salty, sour, bitter, umami, and sweet.

Which tastes primarily use ionotropic mechanisms according to lecture?

Salty and sour.

What does an ionotropic taste mechanism involve?

Ion channels.

Which ion is especially important for salty taste?

Sodium.

How can sodium activate a taste cell?

Sodium activates or enters through an ion channel and produces electrical activity.

Does sour use exactly the same mechanism as salty?

No, sour uses a different ion-channel mechanism.

Which tastes primarily use metabotropic mechanisms according to lecture?

Bitter, umami, and sweet.

What type of receptors are involved in metabotropic taste transduction?

G protein-coupled receptors.

What happens after a chemical binds to a metabotropic taste receptor?

A second-messenger process activates the taste cell.

What example did the professor give for bitter taste?

Coffee.

What type of taste is umami?

Savory.

What type of molecules are associated with umami?

Amino acids.

What food additive did the professor associate with umami?

Monosodium glutamate (MSG).

What does recent research suggest about umami transduction?

Umami may use both ionotropic and metabotropic mechanisms.

What possibility did the professor mention for salty and sour transduction?

Undiscovered metabotropic mechanisms may also exist.

What does changing research on taste transduction demonstrate?

Scientific understanding of taste mechanisms is still developing.

What did the jelly bean experiment demonstrate about taste alone?

Taste can identify sweetness without identifying the specific flavor.

What happened when smell was restored during the jelly bean experiment?

The cherry flavor became recognizable.

What does the jelly bean experiment demonstrate about flavor?

Flavor depends on multiple sensory systems.

What is neurogastronomy?

The study of how sensory systems combine to create flavor.

Which three sensory systems did lecture combine to explain flavor?

Taste, smell, and somatosensation.

Why can smell provide much more variety than the five basic tastes?

Humans have hundreds of different olfactory receptor types.

About how many olfactory receptor types do humans have according to lecture?

About 300.

How many different smells can combinations of olfactory receptors distinguish according to lecture?

Millions.

How can a limited number of olfactory receptor types represent many odors?

Different combinations of receptor activation represent different odors.

What is olfaction?

The chemical sense of smell.

What are odorants?

Chemicals perceived as smells.

How do odorants reach the olfactory system?

Odorants enter through the nose or mouth and reach the olfactory epithelium.

What are major functions of olfaction?

Finding desirable food, avoiding dangerous substances, and distinguishing environmental chemicals.

What role may olfaction have played in mammalian evolution?

Olfaction may have contributed to expansion of the mammalian brain.

How does rodent cortical investment in smell compare with human cortical investment?

Rodents devote proportionally more cortical tissue to olfaction.

How many odors can humans detect according to the textbook?

As many as 10,000.

How chemically complex can natural odors be?

Natural odors can contain hundreds of different molecules.

Where is the olfactory epithelium located?

Near the top of the nasal cavity.

What is the olfactory epithelium?

An epithelial sheet containing olfactory neurons and supporting cells.

About how much of the nasal-cavity surface does the olfactory epithelium line?

About half.

What tissue covers the remaining nasal surface?

Respiratory epithelium similar to tissue in the trachea and lungs.

What are other names for olfactory receptor neurons?

Olfactory receptor cells or olfactory sensory neurons.

What type of cells are olfactory receptor neurons?

Bipolar cells.

What is found at the basal end of an olfactory receptor neuron?

A small-diameter, unmyelinated axon.

What is found at the apical end of an olfactory receptor neuron?

A dendrite ending in a knoblike structure.

What extends from the dendritic knob of an olfactory receptor neuron?

Olfactory cilia.

Where do olfactory cilia extend?

Into the mucus covering the olfactory epithelium.

Where are odorant receptors located?

On olfactory cilia.

What two major functions do olfactory cilia perform according to lecture?

Recognize odorants and transduce chemical signals.

What happens to inhaled odor molecules before receptor detection?

Odor molecules dissolve in mucus.

What does sniffing accomplish in olfaction?

Brings more air and odor molecules into the nasal cavity.

What functions does olfactory mucus serve?

Protects cells, allows cilia to contact odorants, and helps control the ionic environment.

What structures produce olfactory mucus?

Bowman's glands.

What is the nasal mucosa?

The mucus layer, olfactory epithelium, receptor neurons, and supporting cells.