Sensory Two - Olfactory and Taste

Question 1

What does the ability to discriminate two point touch rely on?

Answer 1

The receptive field or receptors and their density.

Question 2

Is receptor density uniform throughout a sensory organ?

Answer 2

No it is not

Question 3

Why are receptors in a sensory organ not uniform?

Answer 3

They may be localized to give higher definition

Question 4

How is intensity of a stimulus encoded generally?

Answer 4

BY the number of receptors activated and the frequency of their firing.

Question 5

Where does all sensory information go to?

Answer 5

The thalamus before it is relayed

Question 6

What do afferent pathways in sensory systems carry information about?

Answer 6

The detected stimulus (single type of stim, not bundled together)

Question 7

Describe the neuron structure between the receptor and the cortex?

Answer 7

Polysynaptic pathways

Question 8

What do chemical sense allow?

Answer 8

Identification of food, noxious stimuli and mates

Question 9

What are two human sense that are chemoreceptive?

Answer 9

Olfaction

Gustatory

Question 10

Where are the receptors located for gustation?

Answer 10

Chemoreceptors are localized to papillae

Question 11

Gustation and olfaction, differ how?

Answer 11

They are separate pathways but compliment one another

Question 12

Whats the density of taste receptors?

Answer 12

50-150 taste receptors per a taste bud.

Thus 2000-5000 taste receptors per a tounge

Question 13

How do taste receptors on each papillae respond to different concentrations of stimuli?

Answer 13

Very selective at low concentrations, less so at higher ones.

Question 14

The taste chemoreceptors are found where on the pipillae?

Answer 14

In taste pores and have a turnover rate of around 2 weeks.

Question 15

What to gustatory chemoreceptors synapse with?

Answer 15

They synapse with gustatory afferent axons.

Question 16

Whats unique about the tongue with regards to taste specificity?

Answer 16

The tounge is divided into five areas of taste. They somewhat overlap as no clear border is formed, like 99% of things in bio

Question 17

What are the three types of gustatory receptor cells and what taste do they detect?

Answer 17

Type One: Salty
Type Two: Sweet, Better, Umami
Type Three: Sour

Question 18

Salty and sour (acid) use what sort of receptors?

Answer 18

Ion channels

Question 19

Describe the transduction of salt taste into perception of salty goodness?

Answer 19

Salt (Na) influxes through the ion channel, depolarizing the membrane causing Ca influx through voltage gated Ca channels and thus neurotransmission onto the gustatory afferent axon.

Question 20

Describe the transduction of sour (acid) taste into perception of sourness?

Answer 20

Acid (H) influxes through the ion channel, inhibiting K efflux thus depolarizing the membrane causing Ca influx through voltage gated Ca channels and thus neurotransmission onto the gustatory afferent axon.

Question 21

What sort of receptors do Sweet, Bitter and umami use?

Answer 21

GPCRs

Question 22

What does chemointeraction with GPCRs result in?

Answer 22

The activation of phospholipase C, IP3 and or other secondary messangers.

Resulting in the opening of Na channels, depolarisation and thus Ca channels open and neurotransmission occurs

Question 23

What GPCR specifically does bitterness use?

Answer 23

T2R (30 types)

Cant distinguish bitterness only that it is bad

Question 24

What GPCR specifically does sweetness use?

Answer 24

T1R

• Requires two T1R receptors together (T1R2 and T1R3) together to detect sweetness

Question 25

What GPCR specifically does umami use?

Answer 25

Umami is the detection of amino acids

Requires two T1R receptors (T1R1 and T1R3)

Question 26

Are the gustatory afferent axons the same for every taste receptor?

Answer 26

No they are specific to the taste

Question 27

Where does gustatory information project to in the brain?

Answer 27

Firstly to the ventral posterior medial nucleus of the thalamus which relays it the the cerebral cortex

Question 28

Polysynaptic pathways for gustation are found in which cranial nerves?

Answer 28

7 (facial)
9 (Glossopharyngeal)
10 (vagus)

All cary gustatory fibres which innervate the NTS then the Thalamus

Question 29

What areas of the cerebral cortex are dedicated to gustation?

Answer 29

Frontal operculum and insular cortex

Question 30

What sort of receptors are olfactory receptors?

Answer 30

GPCRs

Question 31

How many odours are each receptor specialized to?

Answer 31

One or Two

Question 32

How is the olfactory organ organized?

Answer 32

The olfactory organ located in the upper nose is organized into zones which express a particular subset of receptor genes

Question 33

Describe the olfactory pathway

Answer 33

Olfactory receptors
Olfactory  Bulb
Several cerebral targets before all innervating either the:
- Thalamus
- Hypothalmus
- Orbitofrontal cortex

Question 34

Any receptor that is continuosly stimulated does what?

Answer 34

Adapts and stops firing i.e why bad smells cant be smelt after a while. In the case of light source, they fatigue and stop firing.

Question 35

Similar olfactory receptors do what?

Answer 35

Innervate the same glomeruli in the olfactory bulb

Question 36

Increasing the concentration of odour does what to the olfactory receptors?

Answer 36

Increases their rate of firing

Question 37

What is a unique property of the olfactory organ caused by its structure?

Answer 37

It may also be directional