ex. epinephrine in heart cell causes increased heart rate, epinephrine in liver cell causes breakdown of liver glycogen
signal pathways that act on proteins and structures that are already established and take seconds or less (ex. nerve cells, muscle cells, respiratory system)
signal pathways that have to create new proteins and take hours or longer (ex. cell growth and development, digestion)
long distance signaling used throughout the body, often hormones through blood stream
signal molecule stays local and only affects targets in that area (ex. swelling, immune responses, tumor formation and growth, some fetal development)
fast, specific pathways carried out by neurotransmitters
cell signaling to a cell in contact, very localized, signal molecule is often membrane-bound (ex. fetal development)
small hydrophobic molecules can only get to these (ex. Nitrogen Oxygen (NO) does this because it is so small)
more common, takes larger signal molecules that can't fit through a membrane
adding or removing a phosphate to turn on or off a signaling pathway inside the cell (ex. tyrosine kinases)
