BI110 Chapter 20: Module 20
Document Summary
Cells communicate with each other in response to environmental cues. Cues that stimulate responses and communication include light or heat, touch or pressure, and most frequently chemicals. The underlying mechanism used by cells to share information is signal transduction, which produces cellular responses to extracellular signals. Chemical cell signaling in multicellular eukaryotes involves information exchange between neighbouring cells as well as with those farther afield. Cells that respond to a stimulus are called sensory cells. These cells secrete ligands, signaling molecules that bind directly to receptors on target cells to produce biological responses. The assortment of signaling molecules includes hormones, chemical messengers secreted by glands, and neurotransmitters, chemicals produced by the nervous system. Autocrine signaling targets receptors in the same cell that originated the signal. Paracrine signaling targets cells near the signaling cell (diffuse through extracellular fluid to reach their destination). Endocrine signaling involves hormones that target distant cells. Adjacent cells can use direct contact to communicate locally.
