Olfaction and taste Flashcards
Layers of the olfactory/smell system
Cribriform plate
olfactory epithelium
Olfactory sensory neurones
Why do you loose your sense of smell with covid?
damage to the cells that support and assist the olfactory neurons
Stages of the olfactory system
Olfactory bulb-PC(3 layered)-Thalamus- Associational cx
What feature does olfactory pathway have that other sensory pathways have?
No mandatory thalamic relay-
How many olfactory receptor neurone do we have compared to other mammals
Humans have a low amount around 12 million
odour dimensionality
This is when you smell something certain parts of the olfactory system is triggered
Humans can distinguish around 10^27 odours
Experiment with olfaction
Man and dog asked to track scent over loud periods of time
Overtime both dog and human got better
Dog was significantly quicker and more efficient
What does sensitivity to odours depend on
Concentration
hyposmia
Lack of olfactory sensitivity also presented in Parkinson’s disease
Anosmia
Lack of smell and taste also presented in Parkinson’s disease
Pheromones
Animals have a system of smell to report evolutionary fitness
ORNs(olfactory receptor neurones)
Bipolar neurones with connections to colliery and mucus layer
They are supported by basal cells
ORN issues
They are placed in a risky position and can easily be damaged but are slowly replaced
Where can you measure receptor potential in ORNs
Cilia of receptor neurone
Olfactory G protein
G protein binds to terminus C causing the release of cAMP which activates cyclic nucleotide gated channel allowing passage of na+ and ca2+
Ordarant receptor proteins
Genes associated with smell are TM1-TM7
Mechanism of odourant transduction?
odourant molecule binds to receptor-Active G protein- GTP activates cAMP-opens sodium and calcium channels-Chloride channel opens and diffuses out
olfactory glomerulus
axons of many olfactory receptor cells converge on an individual glomerulus in the olfactory bulb, where they make contacts with the distal dendrites of mitral and tufted cells.
Only 1 or 2 are activated by an odour
Mitral cells
Projection neurones
3 reasons for tase
Is it edible
Is it dangerous
Preparation for digestion
Taste system
T
Taste system
Taste buds send signal through cranial nerve to solitary tract to the thalamus
Different types of taste
Sour
Bitter
Salty
Sweet
Types of taste receptor cells
Type I- detects salty things In mouth releases potassium ions and re-uptake of glutamate
Type II- detects sweet and bitter cause release of ATP and release serotonin
Type III-Activate the presynaptic cell and promotes transmitter release
sensory transduction in taste cell stages
Odourant binds to villi
Secondary messengers cause membrane depolarisation
release of multiple transmitters
Action potential is received from postsynaptic neurone
Signal is sen to cortex
What type of molecule opens up GPCR?
sugary molecules open up GPCR(heteromeric complexes/2 subunits) and activate TRMPM5
Taste experiment
Different genes were deleted in order to test if they are responsible for certain taste
Gene responsible for sweet taste is T1R2
