AP BIOLOGY

Detailed explanation-1: -In endocrine signaling, the signaling molecules (hormones) are secreted by specialized endocrine cells and carried through the circulation to act on target cells at distant body sites.

Detailed explanation-2: -Multiple hormones such as ghrelin, leptin, cholecystokinin, and other peptides all relay peripheral signals to the hypothalamus.

Detailed explanation-3: -There are four categories of chemical signaling found in multicellular organisms: paracrine signaling, endocrine signaling, autocrine signaling, and direct signaling across gap junctions (Figure 9.2).

Detailed explanation-4: -Endocrine signaling is an example of long distance communication between hormone producing cells, tissues and glands and cells that express hormone receptor molecules.