neuroscience - taste and smell

how is sweetness detected?

with a single metabotropic receptor

what is sweetness?

molecules of sugar

how is umami detected?

with a single metabotropic receptor

what is umami?

molecules of glutamate/glutamine

how is bitterness detected?

with 50 different metabotropic receptors that bind different bitter molecules

what is bitterness?

a variety of molecules, like quinine

how is saltiness detected?

with an ion channel that is highly permeable to sodium

what is saltiness?

positive ions like sodium

how is sourness detected?

with an ion channel highly permeable to free protons

what is sourness?

pH level, concentration of free hydrogen ions

how is fattiness detected?

with metabotropic receptors and fatty acid transporters

what is fattiness?

fatty acids

taste buds

contain 20 to 50 taste receptor cells, dedicated to one type of taste, so every cell within a taste bud expresses the same taste receptor protein

do taste receptors have action potentials?

no, they release neurotransmitter in a grade fashion

how often are taste receptor cells replaced?

about every ten days

which tastes are instinctively rewarding?

sweet and umami

which taste is inherently aversive?

bitter

olfactory receptor proteins

metabotropic G protein-coupled receptors

how many odorant receptors do humans express?

about 400

odorant molecules

volatile substances that have a molecular weight in range of approximately 15 to 300, most are lipid soluble and of organic origin

olfactory epithelium

tissue of the nasal sinus that sits underneath the skull and contains olfactory receptor cells

where do olfactory receptor cells synapse?

in glomeruli in the olfactory bulb, which sends axons into the brain

how many odorants can humans recognize?

up to ten thousand

pheromones

molecules released by one animal to signal something to another member of the same species

Lee-Boot effect

when female mice are housed together, their estrous cycles slow down and eventually stop

Whitten effect

pheromones in the urine of male mice can trigger synchronous estrous cycles in groups of female mice

Vandenburgh effect

earlier onset of puberty seen in females housed with males

Bruce effect

tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male