Physiology of olfaction and gustation

Question 1

What is ansomia

Answer 1

loss of sense of smell

Question 2

What is aguesia

Answer 2

loss of sense of taste

Question 3

What are tasants

Answer 3

the chemical compounds that bind taste receptors and impart the primary flavor categories (sweet, salty, bitter, sour, unami)

Question 4

What are odorants

Answer 4

the chemical compounds that bind odorant receptors that impart an odor

Question 5

what is the sensory transduction in taste cells

Answer 5

specialized epithelial cells

chemosensory transduction is initiated on the apical domain and electrical signals are generated at the basal domain

TRansient receptor potential receptors (TRP) and Ion channels serve as the primary messengers

release of neurotransmitters

intracellular calcium release facilitiates the fusion and release of the neurotransmitters

Question 6

Stimulus and neurotransmitter of Sour

Answer 6

Stimulus: H+ ions

neurotransmitter: serotonin

Question 7

Stimulus and neurotransmitter for salty

Answer 7

Stimulus: Na+ binding ENaC

neurotransmitter: Serotonin

Question 8

Stimulus and neurotransmitter for sweet

Answer 8

Stimulus: sugars binding GPCRs

neurotransmittter: ATP

Question 9

Stimulus and neurotransmitter for Unami

Answer 9

Stimulus: Glutamate binding mGluR4 (GPCR)

neurotransmitter: ATP

Question 10

Stimulus and neurotransmitter for Bitter

Answer 10

Stimulus: various compounds binding GPCR

Neurotransmitter: ATP

Question 11

Sensory Transduction in olfactory neurons

Answer 11

Bipolar cells that release glutamate

odorant binds a odorant specific G protein (Golf) which activates a adenylate cyclase producing cAMP thus opening a (CNGC) cation channel allowing for the influx of Na+ and Ca+ this then opens a Ca+ and Cl- channel which allows for Cl- out of the cell further depolarizing the cell

Question 12

What happens as a odor persists

Answer 12

as an odor persists sensitivity of the CNGC to cAMP decreases reducing the cation influx all due to enzymatic activity

or a odorant receptor gets phosphorylated over time to become adapted to the smell

Question 13

Hyposima

Answer 13

thickened mucus blocks the odorant receptors making it harder to smell things

Question 14

What are the nutritional values for each taste: Sweet

Answer 14

sweet signals the presence of carbohydrates that serve as an energy source

Question 15

What are the nutritional values for each taste: Salty

Answer 15

Salty taste governs the intake of Na+ annd other salts essential for maintaining the bodys water balance and blood circulation

Question 16

What are the nutritional values for each taste: Umani

Answer 16

Umani is generally believed to reflect a foods protein content due to the presence of glutamate and other amino acids

Question 17

What are the nutritional values for each taste: Sour

Answer 17

sour taste signals the presence of dietary acids

spoiled foods often are acidic and thus avoided

Question 18

What are the nutritional values for each taste: Bitter

Answer 18

thought to gaurd against consuming poisons

since it is so important these bitter tuned GPCR bind with high affinity compared to other taste receptors and need for low concentration to better prevent ingestion of poisons

Question 19

What happens to gustatory and olfactory sensitivity with age

Answer 19

Declines with age

therefore adults eat food with more salt and spices which can be problematic for individuals that have hypertension and or electrolyte issues

Question 20

What is the significance of sugar with infants

Answer 20

babies are primed to the taste of amniotic fluid which reflects the composition of the maternal diet and therefore helps localize the rooting for breastmilk after birth

however newborns respond to sweet tastes and will cause relaxation and decreased heart rate of the infant therefore sweet tastes act as a analgesics if the infant has to do minor painful procedures

this is thought to activate the endogenous opioid system (beta endorphin release)

Question 21

How does sugar help with taking medicine

Answer 21

Most medicines taste bitter to an individual and trigger the bitter receptors

however masking with sodium salts (monosodium glutamate and sodium gluconate) suppress bitter taste at the level of the receptor

Sugar suppresses the bitterness at the cognitive level

Question 22

what is the function of the Nucleus of the solitary tract

Answer 22

receives multiple sensory inputs from vagus nerve that relays information about the viscera. Early site of gustatory and visceral information . reflex forms basis for salivary secretions, mimetic responses and swallowing

Question 23

what is the function of the ventral posterior medial nucleus of the thalamus

Answer 23

relay station for taste perception. The discriminitive aspects of taste are processed here

Question 24

what is considered the gustatory cortex

Answer 24

Insular taste cortex, operculum of the frontal lobe, post central gyrus

Question 25

What is the function of the hypothalamus and the amygdala

Answer 25

affective aspects of eating, emotional context to eating, memories of eating (amygdala)
Integration of homeostatic mechanisms of eating like hunger (hypothalamus)

Interplay between eating and the calming effects of food take place in the limbic and reward system

Question 26

What is the function of the orbitofrontal cortex

Answer 26

Integrating visual, somatosensory, olfaction and gustatory stimuli to collectively appreciate the flavor of food

Question 27

What is the perception of flavor

Answer 27

requires gustatory input, olfactory input, and somatosensory information which come together in the medial orbitofrontal cortex

Question 28

what is the function of the Anterior olfactory nucleus

Answer 28

Relay station to the ipsilateral and contralateral corticies

Question 29

What is the function of the priform cortex and the lateral hypothalamus

Answer 29

control of appetite and how olfactory input influences appetite and hunger

Question 30

What is the function of the piriform cortex and the medial orbitofrontal cortex

Answer 30

integration of sight, smell, and taste of food. appreciation of the flavor of food

Question 31

What is the function of the anterior cortical amygdaloid nuclei

Answer 31

emotional learning, olfactory fear conditioning

Question 32

What is the function of the periamygdaloid cortex

Answer 32

integration of the emotional aspect of food as elicted by odor

Question 33

What is the function of the entorhinal cortex and the hippocampus

Answer 33

memory formation and how olfactory input facilitates both memory and recall

connections within the limbic system and entorhinal cortex are responsible for highly evocative experience of memory upon odor sensation

Question 34

What are the layers of the olfactory bulb

Answer 34

olfactory epithelium

cribiform plate

GLomerular layer: contain olfactory glomerulus and periglomerular cells which release GABA to specify the signal

External plexiform layer: contain tuft cells which project to olfactory tract

Mitral cell layer: mitral cells that project to the olfactory tract

Granule cell layer: contain granule cell which release GABA to help specify the signal

Olfactory tract
(superior)

Question 35

What is the significance of loss of smell and neurodegenerative disease

Answer 35

Loss of smell has been shown as early prognosis of individuals with Parkinson disease

Olfactory testing is used as a biomarker for early diagnostic testing against neurodegenerative diseases