Cells can send messages to themselves or to other cells in three main ways: autocrine, paracrine, and endocrine signaling.
1. Autocrine signaling
- The cell sends a signal to itself.
- The hormone or chemical acts on the same cell that made it.
Example: An immune cell releases a chemical that makes it divide faster.
Simple idea: The cell talks to itself.
2. Paracrine signaling
- The cell sends a signal to nearby cells.
- The signal does not travel in the blood; it acts only on nearby tissues.
Example: Nerve cells sending messages to nearby muscle cells.
Simple idea: The cell talks to its neighbors.
3. Endocrine signaling
- The cell (in an endocrine gland) releases a hormone into the blood.
- The hormone travels a long distance to reach target cells in other parts of the body.
Example: The pancreas releases insulin to control blood sugar in the body.
Simple idea: The cell sends a message through the blood to faraway cells.
In short:
- Autocrine → self
- Paracrine → nearby
- Endocrine → distant