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.

Papillae Structure

Nutrition

1. Cue logs due tomorrow2. 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; depolarizes membrane

• Bitter: –Substance binds with receptor, activates gustducin

which activates phosphodiesterase; which in turn destroys cyclic AMP. • This closes K+ channels, depolarizing membrane

Chemoreception