7. The Chemical Senses Flashcards
What is JND?
Just Noticeable Difference: The detection threshold of the concentration of odorants.
What is identification of odours like without visual cues?
Poor, but when given a choice of options the performance is often perfect. This shows how important contextual information is.
What’s the relationship with smoking and identifying odours
Negative relationship
What’s the relationship with age and identifying odours?
Relatively constant until 70 where there is a steep drop off.
How many types of olfactory receptor neurones (ORN) are there?
350
How many types of olfactory receptor neurones (ORN) are there?
350
How many of each olfactory receptor neurones (ORN) are there?
10,000-20,000
What are GPCRs
G-protein coupled receptors
How does the olfactory system work?
- Odorant molecules dissolve into mucus
- Bind to olfactory receptors
- Open calcium and sodium channels resulting in their influx
- If the concentration of odorant molecules is high enough the membrane will depolarise resulting in an action potential
- AP goes to glomeruli in the olfactory bulb
- AP then goes to higher cortical areas.
What is the piriform cortex known as?
The primary auditory cortex
What does the piriform cortex do in the olfactory system?
- Receives signals from olfactory bulb
- Anterior piriform cortex: produces representations of features of the chemical structure of odorants.
- Posterior piriform cortex: produces representations of the quality of an odour overall.
What does the piriform cortex do in the olfactory system?
- Receives signals from olfactory bulb
- Anterior piriform cortex: produces representations of features of the chemical structure of odorants.
- Posterior piriform cortex: produces representations of the quality of an odour overall.
- After repeated neural activation related to the same odour, neural connections can form between each component.
What does the amygdala do in the olfactory system?
- Activated by emotional stimuli such as pleasant and unpleasant smells
- Sends signal to hypothalamus
What does the entorhinal cortex do in the olfactory system?
- Gateway to the hippocampus (memory)
What does the orbitofrontal cortex do in the olfactory system?
- Receives signals from the amygdala (emotions), piriform cortex (representations of odour) and entorhinal cortex (hippocampus gateway).
- Evaluates incoming stimuli as positive or negative.
What are the five taste sensations?
- Sweet
- Salty
- Bitter
- Sour
- Umami
What is taste onset?
How the taste unfolds over time.
What is taste intensity?
Proportional to the concentration of tastants and therefore activity in the taste-responsive neurones.
What is taste hedonics?
Whether a taste sensation is perceived as pleasant or unpleasant.
What is taste localisation?
Where in the mouth the taste is sensed.
What are the four types of papillae?
- Fungiform
- Filliform
- Circumvilliate
- Foliate
What are the four types of papillae?
- Fungiform
- Filliform
- Circumvilliate
- Foliate
Where are the papillae found?
- Fungiform
- Filliform
- Circumvilliate
- Foliate
- On the tounge.
- Fungiform: front of the tounge
- Filliform: middle of the tounge
- Circumvilliate: back of the tounge
- Foliate: back of the tounge on the sides
Which papillae contain taste buds?
- Fungiform
- Filliform
- Circumvilliate
- Foliate
- Fungiform: YES
- Filliform: NO
- Circumvilliate: YES
- Foliate: YES
Describe taste buds
- Contain taste cells
- Taste cells have receptor sites on their tip.
Describe the pathway of mouth to brain
- Tongue
- Nucleus of the solitary tract (gustatory nucleus)
- Thalamus
- Insula (which projects to the amygdala, orbitofrontal cortex and hypothalamus).
What is the role of the amygdala in taste?
Representation of emotion
What is the role of the orbitofrontal cortex in taste?
Representation of the reward value of food.
What is the role of the hypothalamus in taste?
Representation of hunger.
What components make up flavour?
Taste, olfaction, hunger, thirst, expectation, vision, feeling in the mouth (texture, temperature, dryness).
What is the primary taste area?
Insula
What is the secondary taste area?
Orbitofrontal cortex
What route does flavour take?
The retronasal route.
What is sensory specific satiety?
Pleasantness is rated higher pre-satiety, and unpleasant post-satiety.
What is transduction?
Where molecules activate receptors resulting in neural activity.
