1. Overview of intercellular signaling (c) Autocrine signaling (a) Endocrine signaling Key: Blood vessel o Extracellular signal Receptor ⊙ 9 Membrane-attached Hormone secretion signal into blood by endocrine gland Distant target cells Target sites on same cell (b)Paracrine signaling (d)Signaling by plasma membrane-attached proteins ⑧ Secretory cell Adjacent target cell Signaling cell Adjacent target cell General schemes of intercellular signaling1. Overview of intercellular signaling General schemes of intercellular signaling