Chemical senses Flashcards
What are the functions of chemical senses?
Finding food
Finding a mate
Avoiding dangerous substances
Homeostasis
What are the receptors of chemical senses?
Chemoreceptors
What are the human chemical senses?
Taste (gustation)
Smell (olfaction)
What are the 5 basic tastes?
Salt Sour Sweet Bitter Umami
Where are the taste cells?
Tongue
Palate
Pharynx
What is the structural organisation of taste cells?
Papilla Taste buds Pore Basal cells Taste cells
What is the lifespan of taste receptor cells?
2 weeks
What are the stages from stimulus to action potential in a taste cell?
Chemical behinds Receptor potential Depolarisation Voltage gated Ca2+ Calcium entry Neurotransmitter released Excites sensory neurone Action potential
How is salt detected?
Sodium entry via non-gated channels
Results in depolarisation
How are sour tastes detected?
H+ entry via TRP
Blocks the K+ channel
Results in depolarisation
How are sweet, umami, bitter tastes detected ?
G protein coupled receptors
T1R and T2R families
Which nerves transmit taste?
VII
IX
X
Where does the signal go after the cranial nerves?
To the gustatory nucleus
Then the gustatory cortex
What is ageusia?
Inability to taste
What is neural coding of taste?
Comparing all pathways
What are the secondary pathways of taste?
Swallowing and salivation
What is more sensitive taste or smell?
Smell
What is the combination of taste and smell?
Flavour
Where are smell receptors?
Olfactory epithelium
Describe olfactory cells?
Olfactory cells are neurones
Replaced every 4-8 weeks
Each cell is one type of receptor molecule
Each receptor molecule binds a range of odorants
What is population coding?
Co-ordinated firing of multiple neurones
How are action potentials triggered in olfactory cells?
Odorant binds to receptor G protein mediated events Intracellular cascade Na+/Ca2+ channels open Depolarisation Receptor potential Action potential
Which cranial nerve carries olfactory signals?
I
What is the olfactory pathway?
Olfactory neurons
Olfactory bulb
Olfactory cortex
Recognition/association in the orbitofrontal cortex
