Lecture 19; Olfaction and Gustation

Question 1

Why is smell and taste sensory systems important

in an animals every day life?

Answer 1

To attract and to avoid

Question 2

what key physiological features help us taste and smell what eat?

Answer 2

Olfactory Epithelium
Orthonasal Olfaction
Retronasal olfaction
Retronasal passage

Question 3

What is the olfactory bulb?

Answer 3

Olfaction begins when odorant molecules enter the nasal cavity through inhalation or by rising from the mouth

The molecules interact with the receptors and intracellular process occurs until an action potential is released.

The axons terminate in the dendrites - glomeruli

Question 4

Explain Transduction mechanism

of olfactory receptor cells?

Answer 4

takes place in the cilia
the mucus diffuses through by binding to olfactory receptor protein.
A G protein is activated and targets adenylyl cyclase
Which converts ATP into cAMP
The increase of cAMP causes calcium channels to open and an influx of calcium
This inadvertently depolarises the ciliary membrane

Question 5

What can each olfactory receptor recognise?

Answer 5

multiple odours

Question 6

What can each odour be detected by?

Answer 6

different ORs

Question 7

What can different odours be recognised by?

Answer 7

different combinations of ORs

Question 8

What do axons from functionally similar ORNs converge into?

Answer 8

the same glomerulus

Question 9

What does the glomeruli organisation within a bulb represent?

Answer 9

represents a map of odor-processing information

Question 10

What does the olfactory bulb use large responses of ORNs to encode what?

Answer 10

encode specific stimuli and activate specific areas in the brain

Question 11

Explain the action of tuning an olfactory bulb?

Answer 11

Receptors vary in their breadth of tuning: some are broadly tuned, responding to many odors, whereas others are narrowly tuned, responding to few.

Question 12

Where does the olfactory bulb project to?

Answer 12

Frontal cortex
Hypothalamus and thalamus
Hippocampus

Question 13

Which nerves are associated with taste?

Answer 13

Vagus
Glossopharyngeal
Chorda Tymphani

Question 14

Which receptors are on the tongue?

Answer 14

Circumvallate papillae
Foliate Papillae
Fungiform Papillae

Question 15

Where do the nerves and receptors associated with taste project to?

Answer 15

Brain stem
Thalamus
Insula (primary taste cortex)
Orbitofrontal cortex

Question 16

Describe the tastes there are receptors for?

Answer 16

Umami (savoury)
sweet
bitter
sodium (salty)
sour and carbonation cells

Question 17

What is taste transduction?

Answer 17

is the process of a physical chemical stimulus becoming a neural signal

Question 18

Explain taste transduction through ion channels?

Answer 18

Activation of ion channels are usually perceived as a salty or sour taste

Question 19

Explain taste transduction metabotropically?

Answer 19

is usually perceived as a sweet or bitter neural taste.

Question 20

When does ionic transduction occur, in regards to taste?

Answer 20

occurs when salty chemicals in food or drink enter the taste cell and depolarize the cell by making the cell more positive

Question 21

How do sour chemicals produce depolarisation?

Answer 21

by blocking potassium(K+) ionotropic channels in the taste cells

Question 22

Why does blocking potassium lead to action potential?

Answer 22

These increases in voltage make the cell more positive until a specific voltage is reached at which neurotransmitters are released

Question 23

What is metabotropic transduction in taste?

Answer 23

Metabotropic transduction is a lock and key system

These chemicals bind to metobotropic binding sites on taste receptor cells, causing the release of a G-protein.

The G-protein then leads to the release of a neural signal.
There has been evidence for taste cell specific G-
proteins

Question 24

what is sensory modality?

Answer 24

one aspect of a stimulus or what is perceived after a stimulus

Question 25

What triggers immediate thirst?

Answer 25

Activation of excitatory neurons in the subfornical organ

Question 26

Which neurones control thirst?

Answer 26

CamKII-positive subfornical organ (SFO) neurons

Question 27

Activation of what supresses thirst?

Answer 27

Activation of Vgat-positive neurons in the SFO

Question 28

Examples of sweetness?

Answer 28

Saccharine - Ira Remsen 1879

Cyclamate

Aspartame

Question 29

What did David and Smithers find out about sweetness?

Answer 29

Obesity “epidemic” occurred over the same years as the introduction of low calorie foods into the American market