S&P Exam 3: Chemical Senses

What is neurogenesis?

the constant renewal of chemical receptors

Name the five basic taste qualities.

salty, sour, sweet, bitter, umani

What is the function of sweetness?

substances that have nutritive value

What is the function of bitter?

substances that are potentially harmful

What is the function of saltiness?

sodium is a signal that the body needs to be replenished

List the four types of papillae on the tongue

– Filiform – cone-shaped, entire surface

– Fungiform – mushroom-shaped, sides and tip

– Foliate – folds, back and sides

– Circumvilliate – flat mounds, trench in back

Describe the Filiform.

cone-shaped, entire surface

Describe the Fungiform.

mushroom-shaped, sides and tip

Describe the Foliate.

folds, back and sides

Describe the Circumvilliate

flat mounds, trench in back

How many taste buds are located on the papillae

10,000

Each taste bud has ___ to ____ taste cells with tips that extend into the _____ ______.

50-100, taste pore

Describe the transduction process for taste cells.

Transduction occurs when chemicals contact the receptor sites on the tips of the taste cells.

Electrical signals generated in the taste cells are transmitted from the tongue toward the brain through (4) different nerves:

– Chorda tympani nerve - front and sides of tongue

– Glossopharyngeal nerve - back of tongue

– Vagus nerve - mouth and throat

– Superficial petronasal nerve - soft palate

From there the signals travel to the thalamus and then to two area in the frontal lobe (insula and the frontal operculum)

True/False: All of the papillae except for the filiform papillae contain taste buds.

true

Name the (4) nerves that transmit signals from the taste cells.

– Chorda tympani nerve - front and sides of tongue

– Glossopharyngeal nerve - back of tongue

– Vagus nerve - mouth and throat

– Superficial petronasal nerve - soft palate

The chroda tympani nerve transmits signals from

the front and sides of tonge

The ______________ _______ transmits signals from the back of the tongue

glossopharyngeal nerve

The vagus nerve transmitts signals from the ______ and _______.

the mouth and throat

The _______ ______ _____ transmitts signals from the soft palate.

superficial pentronasal nerve

Chorda tympani nerve, Glossopharyngeal nerve, Vagus nerve, and Superficial petronasal nerve make connections in the _______ of the _________ _______ in the brain stem.

nucleus of the solitary tract

What areas of the brain make up the primary taste cortex in the

frontal lobe?

– Insula

– Frontal operculum

Describe perceptual and physiological differences between non-tasters, tasters, and supertasters (3). How do you test whether someone is a supertaster (2) ?

Phenylthiocarbamide (PTC) or 6-n-propythiouracil (PROP) is adminsttered to test wheter someone is a supertaster

People who can strongly taste PTC are supertasters and those that cannot are called non-tasters

1. Tasters have more taste buds than nontasters

2. Tasters have specialized receptors for these compounds

3. Supertasters appear more sensitive to bitter substances than tasters

Describe the difference between microsmatic and macrosmatic species and give an example of each.

macrosmatic animals have a keen sense of smell, necessary for survival

while, microsmatic animals have a less keen sense of smell and smell is not crucial for survival

Describe the differences in pheromone perception between humans and animals.

Animals use pheromones for mating, alarm, and food trails

In humans, men rate women’s smell as more pleasant when a woman is approaching ovulation.

What are the two stages of olfactory processing.

analyzing and sythesizing

Where do signals go after they leave the olfactory neurons?

the glomeruli in the olfactory bulb

How is the olfactory bulb organized?

into glomeruli which connect to olfactory receptor neurons

How is the piriform cortex organized?

signals from the olfactory bulb are transformed into a scattered pattern of activiation

What is the primary and secondary olfactory areas in the brain? What role does the amygdala play in olfaction?

The primary olfactory area includes the piriform cortex (PC)

The secondary olfactory area includes the orbitofrontal cortex

The amygdala is involved in determining emotional reactions to smell, faces, and pain.

Discuss how odor objects are represented in the brain.

Odor objects are represented by complex neural patterns, organized by chemical similarity, and stored as integrated memory traces.

Formation of odor objects involves linking together the scattered activations for a particular object

After a number of exposures to an object, which causes the same activation pattern to occur over and over, neuron connections form, and the neurons become associated with each other.

What is flavor, and what role does olfaction play in flavor?

Chemicals in food or drink cause taste by activating taste receptors on the tongue. In addition, food and drink release chemicals into the air that reach the olfactory mucosa through the retronasal route.

Flavor is created by interactions among smell, taste, vision, and touch

Which area of the brain are most involved in flavor perception?

insula

Which area of th brain are most involved in flavor detection?

Orbitofrontal cortex

The Orbitofrontal cortex contains ______ _____ which respond to more than one sense with similar qualities.

bimodal neurons

Odor stimuli from food in the mouth reach the olfactory mucosa through

the ________ ________.

retronasal route

Flavor = _____ + ______ + _______

Taste + Smell (+ other sensations)

True/False: The taste of most compounds is influenced by olfaction.

True

The taste of most compounds is influenced by olfaction, but a few, such as __________ are not.

MSG

Vision signals are sent to the _____ and the ______.

orbitofrontal cortex and the amygdala

Touch signals are sent to the _______ and ______.

orbitofrontal cortex and the insula

How does cognition influence flavor? Describe the results and method of the Wine Experiment.

Expectations can influence what you experience and neural responding

In the Wine Experiment, participants in a brain scanner judged the “taste pleasantness: of different samples of wine.

Particpants were asked to indicate how much they liked five different wines, which were identified by their price

In reality there were only three wines: two of them were presented twice, which different price labels

The results showed that particpants rated the wine labled either at $90 as more pleasant than the wine labeled at $10

There were similar ratings were wines with no labels

In addition, labels also influenced the response of the orbitofrontal cortex, with the $90 wine causing a much larger response.

How does satiety influence flavor? Describe the results and method of the Banana Experiment.

Both the pleasantness of a food-related odor and the brain’s response to the odor can be influenced by satiety.

Satiety is defined as (when you don’t want to eat any more)

In the Banana Experiment, participants were tested under two conditions:

1. when hungry

2. after eating bananas until satiety

Participants in a brain scanner judged the pleasantness of a banana and vanilla

The results showed that pleasantness ratings were similar if they were hungry before eating the banana or vanilla

However, after eating the banana until satiety, the pleasantness ratings for the banana decreased much more than vanilla and became negative

Food consumed to satiety is often considered ______ pleasurable than food consumed when hungry.

less

What is food satiey?

(when you don’t want to eat any more)

What is the Proust Effect?

the ability of taste and smell to unlock memories

True/False: Smell cannot induce memory recall.

False

Describe the olfactory experience of newborns and how a mother’s food consumption during pregnancy affects infant food preferences.

Newborns can smell sweet, sour, and bitter stimuli

Prenatally, they experience odors from the maternal diet, which cross into the amniotic fluid and alter its scent. This fetal exposure to flavors (e.g., garlic, carrots, aniseed) increases acceptance and preference for those same flavors after birth.

True/False: Newborns can smell and discriminate between different olfactory stimuli such as sweet, sour, and bitter.

true

What specificing coding? What is it used for?

the idea that quality is signaled by the activity in individual neurons that respond to specific qualities

basic taste qualities

What is population coding? What is it used for?

The idea that quality is signaled by the pattern of activity distributed across many neurons.

Subtle differences between tastes

Describe the Erickson (Rat) Experiment demonstrating population coding.

– Different taste stimuli presented to rats

– Substances with similar neural firing patterns taste similar

Describe the Muller (Mice) Experiement on Specficity Coding.

– Genetic cloning- creates mice with PTC receptors

Cloned Mice with PTC receptors avoided PTC

Normal mice without PTC receoptors did not avoid PTC

True/False: Evidence in rats that single neurons respond selectively to different tastes.

true

________ blocks the flow of sodium into taste receptors

Amiloride

True/False: Salt-dominated neurons are not effected by amiloride.

False (only)

True/False: Evidence only exists for specificity coding and not population coding.

False (both)

True/False: PTC tastes bitter to humans but it is not bitter to mice.

True

_____ of COVID patients experience anosmia. Some experience parosmia.

56%

What is anosmia?

loss of smell

What is parosmia?

change in smell

What are pheromones?

molecules emitted by members of a species that cause specific reactions in other members of the species

What is detection threshold?

lowest concentration at which an odorant can be detected

Dogs are ____ to _____ times more sensitive to smell than humans

300 to 10,000

True/False: Individual receptors for all animals are equally sensitive

True

True/False: Difference between dogs and humans in order detection lies in type and not the number of receptors they have

False

Humans can discriminate between __ ______ odors.

1 trillion

True/False: It is easier to identify an odor

False

True/False: There are individual differences in odor discrimination.

True

Why is it difficult to map perceptual experience onto physical attributes of odorant molecules? (3)

– No specific language for odor quality.

– Molecules with similar structures may smell different.

– Molecules with different structures may smell the same.

Describe the Analyzing stage of Olfactory Processing.

Chemical components are analyzed and transformed into neural activity in the olfactory mucosa and olfactory bulb

Describe the synthesizing stage of Olfactory Processing.

Information is received and synthesized in the olfactory cortex (involves learning and memory)

The Olfactory cortex involves _______ and _______.

learning and memory

The Olfactory _______ conatins olfactory receptor neurons (ORN), which contain the olfactory receptors.

mucosa

True/False: The olfactory mucosa is sensitive to all chemical ordorants.

False (specific range)

Humans have about _______ types of olfactory receptors.

400

Olfactory receptor neurons (ORNs) send signals to the ________ in the olfactory bulb.

glomeruli

Olfactory receptor neurons (ORNs) of a particuar type send their signals to ____ or _____ glomeruli.

one or two

Odorants are coded by patterns of activation of olfactory receptors called ________ ________.

recognition profiles.

Molecules that have similar structures but smell different have (similar/different)_______ recognition profiles. (Choose answer)

different

True/False: Different odorants activate different areas of the olfactory bulb.

True

________ _________ shows that chemicals with longer chain lengths activate areas further to the ______.

Chemotopic map, left

Describe the neural pathways for olfaction. (6)

a. Odorants enter the nose

b. odorants flow into the olfactory mucosa

c. oflactory receptors neurons are stimulated

d. olfactory receptors neurons are activiated

e. olfactory receptor neurons send signals to the glomeruli in the olfactory bulb

f. signals sent to higher cortical areas

The first stage of olfactory processing (analyzing) takes place in the ________ ________and ______ ________.

olfactory mucosa and olfactory bulb

The second stage of olfactory processing (synthesizing) takes place in the ________ _______.

olfactory cortex

Odorants cause _________ activation across the piriform cortex

widespread

_________ ________ are formed when experience with an odor causes neurons in the piriform cortex to become linked.

Odor objects