explain the second messenger pathway of bitter, sweet, and umami cells
when a tastant binds to one of these cells, it activates G proteins, which stiulate the enzyme phospholipase C, thereby increasing production of the intracellular messenger IP3. The IP3 activates a special type of ion channel depolarizing the cell. This depolarization, n turn, causes calcium channels to open, allowing Ca to flow inside. IP3 can also trigger realease of Ca from intracellular storage sites. These two sources of Ca both help trigger neurotransmitter release, thereby stimulating the gustatory afferent axon.