Signaling by secreted molecules
(a) Paracrine: secretory cell releases extracellular signal, which binds to receptor on adjacent target cell, induces change
*Autocrine: target cell is the same as secretory cell; cell secretes extracellular signal, which binds to receptors on ITS p.membrane
(b) Synaptic: nerve cell depolarizes, releases NT into synapse, causes target cell to either depolarize or hyperpolarize, etc. etc.
(c) Endocrine: endocrine gland secretes hormone molecule, which travels via blood stream to distant target cell (binds to rcptr, activates or represses, blah blah blah)