Darkthorn’s Blog

- chemical senses – oldest and most common form of sensory system

- pheromones released for chemosensory information/communication

- reproductive behavior, identification, aggression

- chemoreceptors – generate neural signals on binding with particular chemicals

- provide quality control for injestion

Taste

- tongue, mouth, palate, pharynx, epiglottis

- taste and smell are intertwined to detect flavor

- all tastes are combinations of salt, sweet, sour, bitter (umami)

- taste preferences are inborm and present very early in life

- can develop a taste for certain types of food

- can recognize a deficiency and crave that nutrient

- whole of tongue sensitive to all basic tastes

- threshold concentration for taste

- higher concentration, less selective – specificity lies in the brain

- adaptation to higher levels of the same taste

- 2000 à 5000 taste buds on oral cavity and throat

- tastebuds located along the edge of the papillae

- receptor cell microvilli protrude from pore in chemoreceptor to contact fluid

- dissolved molecules bind to receptor, producing receptor potentials

- depolarizes à open Ca2+ channels à release neurotransmitter

- if large enough, action potentials signal taste to the brain stem

- taste stimuli

- pass through ion channels (sweet and sour)

- bind to and block ion channels (sour)

- bind to a-protein coupled receptors, not voltage gated

- are these neurons? They form synapses and transmit signals….

- saltiness – special Na+ selective channels, not voltage gated

- sourness – acidity with protons, bind to and block K+ channels

- action potentials travel along different pathways to the brain stem

- medulla of brain stem, ventral posterior medial nucleus, gustatory cortex

- population coding – integrate activity across all neurons from tastebuds

Olfaction

- oderants reach the nose through diffusion/sitting/eating

- olfactory nerves of thin unmylinated axons, only one signaling system, opening of cation channels activated Cl- channels to depolarise membrane

- response adapts quickly

- glomeruli ‘smell’ maps for olfactory discrimination