Chapter 14 - The Chemical Senses: Olfaction Flashcards
What is retronasal olfaction?
The sensation of an odour that is perceived when chewing and swallowing
‣ Forces an odourant in the mouth up, behind the palate into the nose
‣ These perception of odours are perceived as originating from the mouth, even though the actual contact of odourant and receptor occurs in the olfactory epithelium
What is taste?
The combination of true taste (Sweet, Bitter, Salty and Sour) and retronasal olfaction
What is an odour?
Translation of a molecule (chemical stimulus) into a sense
of smell
What are odourants?
Molecules that olfactory receptors recognize and respond
to by producing neural signals that the brain represents as
perceptions of different odours
Why are psyhophsyical measurements of olfaction difficult to do?
No clear relationship between the nature of the stimulus and the olfactory perception
- Difficulty of control and delivery of the stimulus
How do pre-existing biases affect how sensitive we are to a smell?
Whether we like the smell or dislike it will cause us to be more sensitive
How are people who have a stronger sense of smell different from people who are average or below?
People who have a stronger sense of smell are better able to discriminate between smells, but are no better at detecting them
What are the gender differences in odour perception?
Women are better at detecting than men in odour identifying tasks
What is receptor adaptation?
Normal biochemical phenomenon that occurs after prolonged exposure to an odourant
‣ Adaptation to odours reduces
sensitivity to that odour
What is cross-adaptation?
Reduced sensitivity to odourants that are chemically or
perceptually similar to odourants to which the person has been continuously or repeatedly exposed
Where does olfaction occur?
through a structure in the olfactory cleft known as the olfactory epithelium
What are olfactory receptor neurons?
Neurons that transduce odourant molecules into
neural signal
What 3 types of cells does the olfactory epithelium contain?
- supporting cells: Provide metabolic support to
the olfactory receptor neurons - Basal cells: Precursor cells to the olfactory receptor neurons
‣ Participate in the continuous replacement of ORN (every
28 days) - Olfactory receptor neurons: Located beneath the olfactory mucus, where their cilia project
How many different types of olfactory receptor neurons are there?
350 different types
What are G-protein coupled receptors?
‣ Ion channels are opened via a secondary messenger system
‣ Depolarizes the cell membrane and sends an action potential that travels up towards the olfactory bulb
