The Chemical Senses Flashcards
what are 3 functions of the chemical substances?
identifying food sources,
avoiding noxious substances,
finding a mate or marking territories.
what are the 5 basic tastes?
salt, sweet, sour, bitter, umami.
explain salty tastes:
salts are vital electrolytes,
ionotropic receptors in receptor cells detect salty tastes,
it is a craved taste.
explain sweet tastes:
we have an innate fondness,
they are usually of high energy foods,
detected by metabotropic receptors in taste receptor cells.
explain sour tastes:
usually of food with high H+ concentrations / acidic foods,
they are aversive to us,
ionotropic receptors detect these tastes in receptor cells.
explain bitter tastes:
instinctively rejected,
often poisons,
we can adapt to like these flavours,
metabotropic receptors in receptor cells detect these tastes.
explain umami tastes:
the savoury taste of glutamate,
it is a taste that is craved,
it is detected by metabotropic receptors in the receptor cells.
what tastes are detected by metabotropic receptors?
sweet,
bitter,
umami.
what tastes are detected by ionotropic receptors?
salt,
sour.
what is the lingual papillae?
area on the tongue where we find our taste buds.
what about the lingual papillae on the back of the tongue?
these are larger and called circumvallate papillae.
what are circumvallate papillae?
are ridges and folds at the back of the tongue containing taste buds.
what about lingual papillae at the edges of the tongue?
these aren’t as large, but there are foliate papillae and fungiform papillae.
what are foliate papillae?
ridges and folds at the edges of the tongue containing taste buds.
what are fungiform papillae?
projections at the edges of the tongue containing taste buds.
why is there more taste detection at the back of the tongue? (simple answer)
there are more taste buds there.
how is the glossopharyngeal nerve (cranial nerve 9) involved in taste?
it carries information about taste at the back of the tongue to to the brain.
how is the chorda tympanic nerve (cranial nerve 7) involved in taste?
it carries info from foliate and fungiform papillae on side and front of the tongue to the brain.
how do chemicals enter the taste bud?
through the taste pore.
explain what this means: the taste receptor cells are polarised.
the apical portion (top) has microvilli where transduction occurs,
signals move down to the basal portion (bottom) where neurotransmitter is released onto gustatory afferents.
what are the membranous receptors that detect salty and sour tastes?
ion channels - ENaC for salty and OTOP1 and proton channels for sour.
what are the membranous receptors that detect sweet, bitter, and umami tastes?
G-protein coupled receptors - T1R2 and T1R3 for sweet, T2Rs for bitter, and T1R1 and T1R3 for umami.
how many types of stimuli do taste cells respond to?
only 1 - they are specific.
how many stimuli do taste buds respond to?
they contain taste cells which respond to various stimuli.
gustatory afferents are separate to taste cells meaning what?
it requires neurotransmitter release across synaptic cleft.
basically describe how the olfactory system detects scents:
odorant molecules enter the nasal cavity and diffuse into mucus surrounding the olfactory epithelium,
this is connected to the olfactory bulb,
which connects to the olfactory cortex.
where are the cilia of the olfactory receptor cells found?
they project into the mucus, and the axonal section projects into the olfactory bulb.
explain how the olfactory receptor cells are bipolar chemoreceptive neruons:
odorants dissolve in the mucus layer,
transduction machinery in the cilia on the dendrites convert these molecules into electrical signals,
the primary afferent is the olfactory receptor cell axon.
what specifically detects odorants?
odorant receptor proteins ORs.
what type of receptors are odorant receptor proteins?
G-protein coupled receptors.
what happens if olfactory receptor cells express the same olfactory receptor proteins?
they converge on to the glomerulus in the olfactory bulb.
what does convergence in the olfactory enable?
enables low concentration of odorants to be detected.
what does convergence in the olfactory enable?
enables low concentration of odorants to be detected.
despite the replacement of olfactory receptor cells, each glomerulus…
each glomerulus will continue to be associated with the same odorant.
second order neurons carry info from the glomerulus to various parts of the brain:
olfactory cortex - conscious smell, hippocampus - olfactory cortex, amygdala - emotional responses, hypothalamus, reticular formation - visceral responses.
