Your Chemical Senses Taste and Smell
When you look at your tongue in the mirror you can see raised areas or “bumps” you are seeing papillae.
Nutrition • Cue logs due tomorrow • Article on taste perception – read and summarize, due Thursday
Taste Bud Structure • Taste buds are made of taste receptor cells • Taste receptor cells have microvilli • Sensitive, microscopic hairs on taste buds • Send chemical signals to brain • The brain interprets the signals and identifies the taste
Chemoreception • Sensory receptors: the presence of certain molecules creates an action potential which is understood by the brain • Action potential: spikes of electrical charge which carry information rapidly to the brain • Neurons are specialized to use changes in membrane potential for fast communication
Action Potentials • There is a difference in value or charges (voltage) across a membrane: it is said that the membrane is polarized • When the membrane potential of a cell becomes less negative than usual, we say that the cell is depolarized.
Chemoreception:Salty and Sour • Salty: Na+ ions • Presence in ion channels depolarizes membrane • Sour: H+ ions • Presence in proton channel closes K+ channels, K+ can’t leave cell, depolarizes membrane
Chemoreception: Bitter, Sweet, Umami • Sweet/Umami: • Substance binds with receptor, activates gustducin which activates the production of cyclic AMP • Cyclic AMP regulates Ca2+ ion channels; calcium causes neurotransmitter release; depolarizesmembrane • Bitter: • Substance binds with receptor, activates gustducin which activates phosphodiesterase; which in turn destroys cyclic AMP. • This closes K+ channels, depolarizing membrane