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Unformatted text preview: Chapter 6 Monday, February 20, 2006 12:36 PM Chapter 6 - Communication, Integration, and Homeostasis Cell-to-Cell Communication • Introduction o OK let's start out really basic. What are the 2 basic types of physiological signals? Which kind is responsible for most of the information in the body? • Electrical signals: changes in a cell's membrane potential • Chemical signals: molecules secreted into the extracellular fluid (ECF) by cells This type of communication is the majority of communication within the body o What are the 4 basic kinds of cell-to-cell communication used in the body? Talk BRIEFLY about each. • Gap junctions: direct cytoplasmic transfer of electrical and chemical signals between cells • Contact-dependent signals: when surface molecules on one cell bind to surface molecules on another cell • Local communication: when chemicals diffuse through extracellular fluid • Long-distance communication: this is done by electrical signals carried by nerve cells (think action potential!) and chemical signals transported in the blood (think hormones!) • Gap junctions transfer chemical and electrical signals directly between cells o Talk to me about gap junctions. • See Figure 6.1, pg. 172 • The idea here is that membrane-spanning proteins on EACH cell called CONNEXINS bind together to create a protein channel called a CONNEXON which allows ions, small molecules (ATP, amino acids, etc.) to flow freely between the two cells (it's kind of like one big cell with 2 nuclei) Note that there are different types of connexins which will form different types of connexons which in turn vary in what they allow to cross • Gap junctions occur in almost every cell type in the body (heart, smooth, whatever) • Contact-dependent signals require cell-to-cell contact o OK now what's up with contact-dependent signals? • As mentioned before, this is when surface molecules on one cell bind to surface molecules on another One type of molecule known for its role in this process is CAM, or CELLULAR ADHESION MOLECULE • This is seen in the IMMUNE SYSTEM and during GROWTH AND DEVELOPMENT • Paracrines and autocrines are chemical signals distributed by diffusion o What is the difference between a paracrine and an autocrine? • A paracrine is a chemical that is secreted by a cell which will diffuse to and act on cells in its IMMEDIATE VICINITY • Whereas an autocrine acts on the cell that secreted it Just to make it interesting, sometimes a chemical can be BOTH a PARACRINE and an AUTOCRINE o What is a good example of a paracrine, and how does it work?What is a good example of a paracrine, and how does it work?...
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This note was uploaded on 04/01/2010 for the course BIOL 373 taught by Professor Vijayan during the Spring '10 term at Waterloo.
- Spring '10