The Chemical Senses Flashcards by Joel Glotfelty

Involves the detection of volatile compounds (odorants) by the olfactory epithelium of the nose

Smell (olfaction)

How well did you know this?

Not at all

Perfectly

An open system capable of adapting and signaling information about an indeterminate environment

Olfaction

How well did you know this?

Not at all

Perfectly

Lost or impaired smell

-Should be taken very seriously

Anosmia

How well did you know this?

Not at all

Perfectly

Continually replaced every 3060 days from the basal stem cell population

Olfactory Receptor Neurons (ORNs)

How well did you know this?

Not at all

Perfectly

Loss of AON, granule or periglomerular neurons may be responsible for impaired olfaction in

Alzheimer’s Disease (AD)

How well did you know this?

Not at all

Perfectly

Odorant discrimination is from the

Orbitofrontal olfactory area

How well did you know this?

Not at all

Perfectly

What are the 4 cortical regions that are activated by olfactory stimulation?

Orbitofrontal cortex, piriform cortex, amygdala, and region of olfactory bulb

How well did you know this?

Not at all

Perfectly

In the central neural pathways mediating olfaction, there is no

Thalamic relay

How well did you know this?

Not at all

Perfectly

The site of sensory transduction

Cilia

How well did you know this?

Not at all

Perfectly

Evoke a depolarizing (inward) current

Odorants

How well did you know this?

Not at all

Perfectly

Are 7 transmembrane (7-TM) G-protein coupled receptors (GPCR)

Odorant Receptors

How well did you know this?

Not at all

Perfectly

Are (heterotrimeric) G-protein coupled receptors

Odorant Receptors (ORs)

How well did you know this?

Not at all

Perfectly

The alpha subunit of ORs is specific to

ORNs

How well did you know this?

Not at all

Perfectly

Odorant binding elicits increases in

Intracellular cAMP levels

How well did you know this?

Not at all

Perfectly

Elevated cAMP stimulates opening of cation channels, leading to

Depolarization

How well did you know this?

Not at all

Perfectly

In OSNs, activated signal transduction molecules are targeted for negative feedback regulation. This causes

Desensitization

How well did you know this?

Not at all

Perfectly

The vast majority of GPCRs display a rapid loss of responsiveness in the continuing or recurring presence of an

Agonist or Stimulus

How well did you know this?

Not at all

Perfectly

Uncoupling of receptor from G proteins in response to receptor phosphorylation causes

Desensitization

How well did you know this?

Not at all

Perfectly

Internalization of cell surface receptors to the cytosol causes

Desensitization

How well did you know this?

Not at all

Perfectly

Likely to be essential for the prevention of cellular transduction machinery saturation, thus allowing high sensitivity retention during continuous or repetitive odor stimulation

Desensitization

How well did you know this?

Not at all

Perfectly

What percentage of human odorant receptor genes are not transcribed (pseudogenes)

About 60%

How well did you know this?

Not at all

Perfectly

Integrates input from many ORNs

The Olfactory Bulb

How well did you know this?

Not at all

Perfectly

Axons of thousands of ORNs expressing the same OR converge at a single

Glomerulus

How well did you know this?

Not at all

Perfectly

A single glomerulus reflects the summed activity of all ORNs that express a single

How well did you know this?

Not at all

Perfectly

This convergence is thought to increase the sensitivity of the

Olfactory System

This convergence is thought to increase the sensitivity of the olfactory system and enhances the signal sent to the brain for activity at each

Receptor

5-25 mitral cell dendrites innervate a single

Glomerulus

Exhibit distinct thresholds for particular odorants, suggesting the perception of an odor can change as a function of its concentration

ORN's

Recognize different features of odorants

ORs

Depends on which receptors are activated and how strongly

Odor Recognition

The array of receptor activation leads to a unique pattern of -Consistent between individuals

Glomeruli Activation

The patterns of activity in the olfactory bulb are transmitted to higher brain regions for

Processing

The cingulate gyrus and orbitofrontal complex are more activated for

Pleasant smells

Intranasal polyposis, chronic rhinitis, allergic rhinitis, and upper respiratory (viral) infections (common cold) are forms of

Nasal/sinus diseases

Posttraumatic anosmia is a clinical sign of

Orbitofrontal damage

Adrenal cortical insufficiency, diabetes mellitus, Kallmann syndrome, and Turner syndrome all cause

Olfactory dysfunction

Alzheimer's and Huntington's Chorea are neurological causes of

Olfactory Dysfunction

Both chemotherapy and radiation treatments target dividing cells and therefore also have dramatic effects on

Chemosensory stem cells

Losses secondary to obstruction of the nasal airflow to the olfactory cleft

Conductive olfactory loss

What are three examples of conditions that cause conductive losses to the olfactory system?

Chronic rhinosinusitis (CRS), allergic rhinitis, and tumors

Losses secondary to damage to or dysfunction of the olfactory nerves anywhere from the olfactory receptors through the olfactory bulb to the processing centers in the brain

Sensorineural olfactory losses

Damage to the olfactory epithelium, the olfactory nerve, the olfactory bulb or olfactory tract can cause

Unilateral anosmia

Destruction of olfactory cortex or olfactory pathways posterior to the trigone (where the tracts divide) must be bilateral to affect

Olfactory Function

Can be difficult to detect due to compensation by contralateral nostril

Ipsilateral Anosmia

Involves the direct contact of water-soluble compounds with tongue pappilae

Taste or Gustation

What is more sensitive, olfaction or taste?

Olfaction

We can detect odorants at nanomolar concentrations (10-9M) while taste requires

Milimolar concentrations

What are the 5 primary taste qualities/modalities?

Sweet, sour, bitter, salty, and umami

Taste cells are clustered into taste buds (~4000 in human oral cavity) on

Lingual Papillae

Three morphologically distinct lingual papillae exist. They are:

Fungiform (25% of taste), Circumvallate (50%) Foliate (25%)

Embedded in pappilae of lingual epithelium and in the oral cavity

Taste Buds

Taste buds open onto the epithelial surface via a

Taste Pore

Are continually being replaced from a basal stem cell population (~2 weeks)

Taste Cells

Taste from the anterior 2/3 of the tongue are from

CN VII chorda tympani branch

Taste from the posterior 1/3 of the tongue is from

CN IX lingual branch

Taste from the epiglottis and posterior pharynx are from

CN X sup. laryngeal branch

Are electrically excitable and can generate action potentials, although they are non-neuronal

Taste Cells

Taste cell activity is relayed via sensory neurons that innervate them at their

Basal Poles

Which tastes act directly on ion channels?

Na+ and K+ (salty) and H+ (sour)

Which tastes act via G-protein mediated intracellular second messenger cascades?

Bitter, sweet, and Umami tastants

Mediated by Na+ influx through Na+ channels

Salty taste

Mediated by the passage of protons through Na+ channels or the blockade of K+ channels

Sour (acids)

Nonvolatile, hydrophilic molecules soluble in saliva

Most taste molecules

Encodes quantitative and qualitative aspects (concentration = flavor intensity)

Taste stimuli

30-40% of people cannot taste the bitter compound

PTC

Taste receptors also adapt to the ongoing presence of a

Stimulus

What percentage of a meals flavor is the result of olfactory input?

80%

Of patients complaining of smell and taste loss, what percentage suffer true gustatory loss?

Less than 5%

Functions in noxious stimuli detection (nociception) (general somatic) -Stimulate polymodal nociceptive fibers

Trigeminal chemoreception

Trigeminal chemoreception is activated by chemical irritants that come in contact with the

Face or Oral cavity

Exposure triggers a variety of responses, including increased salivation, tearing, sweating, decreased respiratory rate, broncho-constriction

Trigeminal chemoreceptor irritants

Blocks ligand-gated ion channels in nociceptive fibers -Can block pain signal

Capsaicin

Many “irritants”can also be perceived as odors or tastes, but the threshold concentrations are much higher for the perception of

Irritating Sensations

For anosmics, the threshold is higher, and the lower level perception is

Absent

Substances which are secreted to the outside by an individual and received by a second individual of the same species, in which they release a specific reaction, for example, a definite behavior or a developmental process

Pheromone

Usually found in urine or glandular secretions

Pheromones

Requirement of VMO in question for a number of pheromone responses, suggesting that some responses can be mediated by the

Main olfactory system

What are the two pheromone receptor genes in rodents that encode 7-TM G-protein coupled receptors?

V1R class and V2R class

Areas that are involved in reproductive and aggressive behaviors are neural pathways for processing

Pheromone signals

What are the neural pathways for processing pheromone signals?

Bed of nucleus of tria terminalis and medial/posterior amygdala

Begins to develop in humans during gestation, but disappears before birth

A VMO (vomeronasal organ)

Humans possess numerous genes that are homologous to vomeronasal receptor genes from lower organisms, but the vast majority appear to be

Pseudogenes

The Chemical Senses Flashcards

(82 cards)