Chemical senses

Question 1

What do smell and taste require?

Answer 1

Contact with the molecules the protect the body from - neurogenesis (1-2 weeks taste, 5-7 weeks smell)

Question 2

What is the importance of taste and smell

Answer 2

Prepare the body for digestion, strongly connected to memory, contribute to “flavour” of food and role of “gatekeeper”

Question 3

What are the functions of taste?

Answer 3

Gatekeeper function to identify what the body needs and detect substances that are damaging

Question 4

What are the 4 basic tastes?

Answer 4

Salty - sodium chloride, sour - hydrochloric acid, sweet - sucrose, bitter - quinine
Umami was later added - meaty taste

Question 5

What is the structure of the taste system?

Answer 5

Tongue contains papillae. Filiform are cone shaped, fungiform are mushroom shaped and foliate are folds. Circumvallate are flat mounds. All papillae contain taste buds except filiform. No taste sensation when centre of tongue is stimulated

Question 6

What are taste buds?

Answer 6

Each bud contains 50-100 taste cells and the tips of these cells protrude into the taste pore

Question 7

What are taste signals?

Answer 7

Transduction occurs at the taste receptors. Nerve fibres from tongue and mouth synapse in the nucleus of the solitary tract. From there to the thalamus and to the frontal operculum and the insula

Question 8

What is cortical processing of taste?

Answer 8

The insula and the frontal operculum (combined gustatory cortex) are considered to be the primary taste cortical areas

Question 9

What is the olfactory system?

Answer 9

Humans are microsmatic so smell isn’t crucial to survival whereas many animals are microsmatic so a good sense of smell is important to survive. Difficulty in relating specific molecules to a smell as molecules with similar structure can be different and molecules with different structures can be similar. Some odours are made up of many molecules

Question 10

How does the olfactory system work?

Answer 10

Each olfactory receptor specific to narrow range of chemicals. Signals are transmitted to the glomerulus and then sent to higher cortical areas

Question 11

What is a chemotopic map?

Answer 11

Different odours cause different patterns of activation. Different features of molecules are represented by different regions on the olfactory bulb. This ‘map’ of odours in the olfactory bulb is known as the chemotopic map

Question 12

What are the brain pathways for smell?

Answer 12

Olfactory bulb to piriform cortex to orbitofrontal cortex to the amygdala, linking to emotion

Question 13

What is the link between the piriform cortex and odours?

Answer 13

Odour objects have the ability to categorise odour even though the composition can differ greatly. The piriform cortex participates to the formation of odour objects, by a process of pattern completion

Question 14

What is flavour?

Answer 14

Flavour is taste and smell. Retronasal olfaction is when the odorant molecules in the oral cavity and pharynx reach the olfactory mucosa. Orthonasal olfaction occurs via the nose

Question 15

What is the link between retronasal olfaction and taste?

Answer 15

Our perception of flavour can be very different with the nostrils open and closed

Question 16

How do taste and olfaction occur in the brain?

Answer 16

Flavour perception is multimodal so taste and olfaction in the brain also interact with vision, touch and sound

Question 17

What is the orbitofrontal cortex?

Answer 17

It’s suggested as a centre for processing flavour. Presence of bimodal neurons responding to more than one sense and neurons often respond to congruent qualities in different modalities

Question 18

What are multisensory interactions?

Answer 18

Congruent colours can enhance taste and flavour intensity increases with colour saturation.