act locally over different type of cells , including themselves
example IL1 in monocyte
signaling cell and target cell are nearly like secretion of local mediator which brings the effect in immediate area of signaling
example : histamines
signaling cell and target cell can far apart it is very slow process
example: secretion of hormone into the blood stream for dispersal like insulin, adernaline
signaling molecule in plasma membrane of a signaling cell interact with membrane bound receptor on the target cell, these cells are therefore restricted to cells which are in direct contact
shortest range system , inhibition of neighbor by differential nerve cells
nerve cells elicit responses by releasing neurotransmitters at synapses
signaling cam work out for very long distance too and is of very fast type
example : GABA