Sensory   transduction   by   a
   sweetness receptor.

   Binding  of  a  sugar  molecule  to a receptor cell initiates a signal
   transduction pathway involving cyclic AMP and protein kinase A.

   K^+ channels in the membrane close, and the membrane depolarizes.

   Voltage-gated calcium Ca^2+ channels open, and Ca^2+ diffuses into the
   receptor cell.

   Synaptic  vesicles  release  neurotransmitters, sending signals to the
   sensory neuron.