Histamine released by immune cells in the bronchial tree makes neighbouring smooth muscle constrict. Which kind of signalling is that?

1. A paracrine is a chemical that produces its response in neighbouring cells. 2. Histamine from bronchial immune cells acts on the smooth muscle next to it, so it is a paracrine. 3. An autocrine acts back on the very cell that released it, which is not the case here. 4. Endocrine signals travel in blood to distant targets, and paracrine concentrations are too low for that. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 17 "The Endocrine System", section 17.1 An Overview of the Endocrine System_