Nervous and Endocrine Systems

What happens when you think?Some technology allows researchers tolook into the body of a living person.As recently as the 1970s, there was no wayfor doctors and scientists to see inside ofthe body without putting a patient throughsurgery. Today, researchers and others usemagnets and computer technology, such asthe MRI scan above, to look at the internalorgans of live patients.ConnectingCONCEPTSAnimals Although onlyvertebrates have a spinalcolumn, most animals haveneurons. Neurons arespecialized cells that sendsignals to different organsystems throughout thebody. Neurons connect thebrain to muscles and othertissues, and some neuronssend such fast signals thatthey can make a personblink in less than one onehundrethof a second.colored LM; magnification 25,000Chapter 29: Nervous and Endocrine Systems 873