20/ the chemical senses Flashcards
are chemical senses new or old
oldest and most common form of sense
functions of chemical sense
- identify food
- avoid noxious substances
- find a mate or mark territories
relationship between gustatory (taste) system and olfactory system
- parallel processing
- merged in the cns
salty - relates to, preference, relevance
- vital electrolytes
- high salt
- required for many physiological processes
sour - relates to, preference, relevance
- acidity H+ content
- avoid high acidity
- avoid rotting food - injury to GI tract
sweet - relates to, preference, relevance
- sugars
- high sugar content
- required for energy and growth
bitter - relates to, preference, relevance
- diverse chemical structures
- avoid bitter
- avoid toxic substances, poison
umami - relates to, preference, relevance
- amino acids like glutamate
- high aa preference
- protein synthesis, neurotransmission
function of lingual papillae and taste buds
- contains taste buds - groups of taste cells
- on tongue - give rough texture
- 4 types
- 2000-5000 taste buds
- 100 chemoreceptive taste cells per taste bud
- taste pore allows sensory transduction by microvilli
taste organs
- tongue, cheeks, soft palate, pharynx (throat), epiglottis (flap of cartilage that stops food getting in lungs)
which flavours are detected by ion channels and which by g protein coupled receptors
- ion channels: salty, sour
- g protein coupled: bitter, sweet, umami
- different current repsonse
foliate vs circumvallate papillae
- foliate: side of tongue
- circumvallate: back of tongue
how are gustatory afferents separate to taste cells
- requires nt release across synaptic cleft
overview of how olfactory physiology works
- olfactory bulb in brain
- odorants dissolve in mucus under olfactory epithelium
- olfactory receptor cells under epithelium
oderants as low as a few parts per … can be detected, area of human olfactory epithelium
- trillion
- 10 cm2
info on olfactory receptor cells
- bipolar chemoreceptive neurons
- odorants must dissolve in mucus layer
- transduction machinery is found within cilia at end of the dendrite
- primary afferent neuron is the axon of the olfactory receptor cell
- axons are thin and unmyelinated
- regularly replaced - vulnerable since cilia project into outside environment
odorant receptor proteins. how many do humans have, how many receptors does a receptor cell express, how do we get specific smells
- 350 - huge amount to a sense we don’t rely on anymore
- receptor cells only express one type of receptor
- one receptor can recognise multiple odorants
- unique combination of receptors allows specific smells
olfactory - how does transduction occur
- via g protein coupled odorant receptor proteins - golfs
- alpha subunit of g protein binds to adenyl cyclase
- ac converts atp into camp
- some ion channels are camp gated - intracellular ligand
- ions move in, cell gets more positive
- calcium acts as intracellular ligand to open another ion channel - calcium gated chloride channels open
- negative chloride out of cell - more positive
whats different about olfactory cells
- more positive to generate ap
- increase in intracellular chloride - chloride moves out, cilia more positive
info about glomeruli of the olfactory bulb
- like nuclei on olfactory bulb
- each glomeruli receives input from only one type of olfactory receptor
- convergence on second order neurons
