taste and smell - perception

Question 1

What are the five basic taste modalities?

Answer 1

Sweet, sour, salty, bitter, and umami.

Question 2

Where are taste buds located and what do they contain?

Answer 2

Taste buds are primarily found on the tongue (within papillae) and contain clusters of receptor cells, supporting cells, and basal cells.

Question 3

How do taste receptor cells transduce chemical signals?

Answer 3

Tastants (chemical stimuli) bind to receptors on taste cells, triggering ion channel opening or G-protein coupled receptor (GPCR) cascades that lead to neurotransmitter release and signal transmission via cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus).

Question 4

What is the role of the gustatory cortex?

Answer 4

It processes taste information relayed from the brainstem via the thalamus, leading to perception of taste quality and intensity.

Question 5

Diagram – Taste Pathway

Answer 5

[Tongue: Taste Buds]
│
[Activation of Taste Receptor Cells]
│
[Cranial Nerves VII, IX, X]
│
[Brainstem Nuclei]
│
[Thalamus]
│
[Gustatory Cortex]

Question 6

What is the olfactory epithelium and where is it located?

Answer 6

A specialized tissue in the nasal cavity that contains olfactory receptor neurones (ORNs) responsible for detecting odourants.

Question 7

How do olfactory receptor neurone transduce odourant signals?

Answer 7

Odorants bind to G-protein coupled receptors (GPCRs) on ORNs, triggering a second messenger cascade (involving cAMP) that depolarizes the cell and generates an action potential.

Question 8

What is the role of the olfactory bulb in smell perception?

Answer 8

The olfactory bulb receives input from ORNs; within its glomeruli, signals are spatially organised and processed before being relayed to higher brain centres.

Question 9

What are two unique features of the olfactory system?

Answer 9

• It bypasses the thalamus, sending signals directly to the olfactory cortex.
• It has a direct connection with the limbic system, linking smells closely to emotion and memory.

Question 10

Diagram – Olfactory Pathway

Answer 10

[Olfactory Epithelium (in nasal cavity)]
│
[Olfactory Receptor Neurons]
│
[Olfactory Bulb (Glomeruli)]
│
[Olfactory Cortex & Limbic System]

Question 11

How do taste and smell work together in the perception of flavour?

Answer 11

Flavour is a multi-sensory experience where taste provides basic modalities (sweet, sour, etc.) and smell contributes the complex nuances; together they form the complete perception of food flavour.

Question 12

What happens when there is impairment in the olfactory system?

Answer 12

Loss or reduction of smell (hyposmia or anosmia) can significantly diminish flavor perception, as smell is a major contributor to taste.

Question 13

What is sensory adaptation in the context of olfaction?

Answer 13

Prolonged exposure to an odour leads to reduced sensitivity or diminished perception due to receptor desensitisation.

Question 14

How often do taste receptor cells regenerate?

Answer 14

Taste cells typically regenerate every 10–14 days, ensuring continual renewal of the sensory system.

Question 15

Uses both ion channel mechanisms (for salty and sour tastes) and GPCR cascades (for sweet, bitter, umami).

Answer 15

Primarily relies on GPCR cascades with cAMP as a second messenger for signal transduction.

Question 16

Compare the transduction mechanisms in taste and smell.

Answer 16

Taste: Uses both ion channel mechanisms (for salty and sour tastes) and GPCR cascades (for sweet, bitter, umami).
Smell: Primarily relies on GPCR cascades with cAMP as a second messenger for signal transduction.