Basic Elements Of Cell Signaling Systems

Cells usually interact with each other through molecules called Extracellular Messenger Molecules. Target cells must express appropriate receptor for first messengers otherwise transduction cannot take place.

1. Autocrine signaling – cell sends out a message to itself, self inhibition or stimulation may take place. It is setting itself up to give itself a message. (Why does it do that? Is it trying to do a self-systems check? Trying to figure out if it has mutated? 'Is there something I am missing?)

2. Paracrine signaling – cell messages local or surrounding cells. Very active and unstable chemicals, often interacts with the Extra-Cellular Membrane ECM). Signal has virtually no longevity once released from the cell. Can be degraded by enzymes.

3. Endocrine signaling – cell (or tissues) message distant cells (through vascular system), called hormones. Target cells are far away (head to toe?).

All Extracellular Messenger Molecules bind to an appropriate receptor.

Side note: there is also a process known as intracrine - interactions within the cell