Smell & Taste Flashcards
What are the 3 characteristics of ‘smelly’ molecules?
- small
- volatile
- hydrophobic
What is the physiology of smell?
Odours bind to olfactory cilia which are a part of the olfactory sensory neuron (OSN) which has a single type of odor receptor
What are 2 problems with the shape theory of olfaction?
- Differences in smells between isotopes
- Some molecules smell the same when their shape is changed
How is smell transmitted to the cortex?
- OSN will fire once 8 binding sites are filled
- Signals sent to the olfactory bulb
- This has a direct line to the cortex
How can we generate so many smells?
- Only 300 types of receptor
- However, combine to generate pattern of activity in the cortex (entorhinal, piriform cortex)
Does the brain respond to smells that are not received?
yes
What is the vomeronasal organ?
- is a parallel olfactory system in many animals
- Contains a separate set of ‘heavy chain’ odorant receptors that bind to pheromones
How is flavour detected?
Retronasal olfaction as well as taste (smells coming from behind the palate)
What are the 5 basic tastes?
- Sweet
- Sour
- Salt
- Bitter
- Unami
What are taste buds?
- contains taste receptor cells embedded in papillae
- covey neural signals to the brain via taste nerves and cranial nerves
How are salt and sour detected?
Ions enter directly through channels
How are sweet and bitter tastes sensed?
- too big for ions, therefore use G couples proteins
What is the labelled lines theory and why is it important?
- Theory of taste coding in which each taste fibre carries a particular taste quality
- Can be used to measure neural responses in primates and predict responses in humans
What is unami caused by?
- MSG (glutamate)
- Can be harmful in large doses to certain sensitive individuals
What other factors influence taste?
- Learned aversions
- Cultural factors
- Visual perception
