olfaction smell

odorants

olfactory system is sensitive to specific molecules called odorants

400 different types

recognize up to 10000 in combos

volatile

lipid soluble and organic

each one sensitive to specific molecule

olfactory receptor cells

contains one receptor protein in each cell

in olfactory epithelium

synapse in glomeruli in olfactory bulb> one glomerulus is one odor

receptor protein

transduce the odorants

release in graded manner, no action potential

metabotropic g protein

pheromones

signalling molecules released by animals to members of the same species

behavioural responses are innately hardwired

why do ants use pheromones

• to signal danger

• to mark a path

• attract/repel members of same species

• signal sexual attractiveness and reproduction activity

pheromone signaling

initial transduction and processing occurs in the vomeronasal organ and the acessory olfactory bulb, parallel to normal ob.

activated by sniffing of mouth and anogenital region

secreted through blood, sweat, urine,

What type of receptors detect pheromones

vomeronasal receptors

who doesnt have pheromone organs

humans, birds, apes

rodent effects

female to male signalling is very powerful

males will only signal to females who are in heat if their vermonosal organ is functional

if its damaged, they’ll try to mate with anyone

male to female effects

more subtle, females will prefer males with healthy testosterone levels

4 effects of pheromones

1. lee-boot effect

2. whitten effect

3. vandenbergh effect

4. bruce effect

   these effects dont happen for castrated males

Lee boot effect

when female mice are housed together with no male present, their estrous cycles will slow down

Whitten effect

the pheromones signals from males can result in synchrous estrous cycles in groups of female mice

Vandenbergh effect

earlier onset of puberty when females are housed with males

Bruce effect

females tend to terminate their pregnancies when they come across an unfamiliar male scent