Lecture 19; Olfaction and Gustation Flashcards
Why is smell and taste sensory systems important
in an animals every day life?
To attract and to avoid
what key physiological features help us taste and smell what eat?
Olfactory Epithelium
Orthonasal Olfaction
Retronasal olfaction
Retronasal passage
What is the olfactory bulb?
Olfaction begins when odorant molecules enter the nasal cavity through inhalation or by rising from the mouth
The molecules interact with the receptors and intracellular process occurs until an action potential is released.
The axons terminate in the dendrites - glomeruli
Explain Transduction mechanism
of olfactory receptor cells?
takes place in the cilia
the mucus diffuses through by binding to olfactory receptor protein.
A G protein is activated and targets adenylyl cyclase
Which converts ATP into cAMP
The increase of cAMP causes calcium channels to open and an influx of calcium
This inadvertently depolarises the ciliary membrane
What can each olfactory receptor recognise?
multiple odours
What can each odour be detected by?
different ORs
What can different odours be recognised by?
different combinations of ORs
What do axons from functionally similar ORNs converge into?
the same glomerulus
What does the glomeruli organisation within a bulb represent?
represents a map of odor-processing information
What does the olfactory bulb use large responses of ORNs to encode what?
encode specific stimuli and activate specific areas in the brain
Explain the action of tuning an olfactory bulb?
Receptors vary in their breadth of tuning: some are broadly tuned, responding to many odors, whereas others are narrowly tuned, responding to few.
Where does the olfactory bulb project to?
Frontal cortex
Hypothalamus and thalamus
Hippocampus
Which nerves are associated with taste?
Vagus
Glossopharyngeal
Chorda Tymphani
Which receptors are on the tongue?
Circumvallate papillae
Foliate Papillae
Fungiform Papillae
Where do the nerves and receptors associated with taste project to?
Brain stem
Thalamus
Insula (primary taste cortex)
Orbitofrontal cortex
Describe the tastes there are receptors for?
Umami (savoury) sweet bitter sodium (salty) sour and carbonation cells
What is taste transduction?
is the process of a physical chemical stimulus becoming a neural signal
Explain taste transduction through ion channels?
Activation of ion channels are usually perceived as a salty or sour taste
Explain taste transduction metabotropically?
is usually perceived as a sweet or bitter neural taste.
When does ionic transduction occur, in regards to taste?
occurs when salty chemicals in food or drink enter the taste cell and depolarize the cell by making the cell more positive
How do sour chemicals produce depolarisation?
by blocking potassium(K+) ionotropic channels in the taste cells
Why does blocking potassium lead to action potential?
These increases in voltage make the cell more positive until a specific voltage is reached at which neurotransmitters are released
What is metabotropic transduction in taste?
Metabotropic transduction is a lock and key system
These chemicals bind to metobotropic binding sites on taste receptor cells, causing the release of a G-protein.
The G-protein then leads to the release of a neural signal.
There has been evidence for taste cell specific G-
proteins
what is sensory modality?
one aspect of a stimulus or what is perceived after a stimulus
What triggers immediate thirst?
Activation of excitatory neurons in the subfornical organ
Which neurones control thirst?
CamKII-positive subfornical organ (SFO) neurons
Activation of what supresses thirst?
Activation of Vgat-positive neurons in the SFO
Examples of sweetness?
Saccharine - Ira Remsen 1879
Cyclamate
Aspartame
What did David and Smithers find out about sweetness?
Obesity “epidemic” occurred over the same years as the introduction of low calorie foods into the American market
