Hockenbury Discovering Psychology 5th txtbk

The Neuron45The NeuronThe Basic Unit of CommunicationKey Theme• Information in the nervous system is transmitted by specialized cells, calledneurons.Key Questions• What are the basic components of the neuron, and what are their functions?• What are glial cells, and what is their role in the nervous system?• What is an action potential, and how is it produced?Communication throughout the nervous system takes place via neurons—cells thatare highly specialized to receive and transmit information from one part of the bodyto another. Most neurons, especially those in your brain, are extremely small. A bitof brain tissue no larger than a grain of rice contains about 10,000 neurons! Yourentire brain contains an estimated 100 billion neurons. Special magnifying equipment,such as an electron microscope, is usually used to study neurons.Neurons vary greatly in size and shape, reflecting their specialized functions. Thereare three basic types of neurons, each communicating different kinds of information.Sensory neurons convey information about the environment, such as light or sound,from specialized receptor cells in the sense organs to the brain. Sensory neurons alsocarry information from the skin and internal organs to the brain. Motor neuronscommunicate information to the muscles and glands of the body. Simply blinking youreyes activates thousands of motor neurons. Finally, interneurons communicate informationbetween neurons. By far, most of the neurons in the human nervous systemare inter neurons, and many interneurons connect to other interneurons.Along with neurons, the human nervous system is made up of other specializedcells, called glial cells or simply glia (see photo). Glial cells outnumber neurons byabout 10 to 1 but are much smaller. Glia is Greek for “glue,” and at one time it wasthought that glial cells were the glue that held neurons together. Although theydon’t actually glue neurons together, glia do provide structural support for neuronsthroughout the nervous system. They also provide nutrition for neurons and removewaste products. Beyond their support functions, it’s now known that some glial cellsplay an active role in brain development and function (Allen & Barres, 2009).biological psychologySpecialized branch of psychology that studiesthe relationship between behavior andbodily processes and systems; also calledbiopsychology or psychobiology.neuroscienceThe study of the nervous system, especiallythe brain.neuronHighly specialized cell that communicatesinformation in electrical and chemical form;a nerve cell.sensory neuronType of neuron that conveys information tothe brain from specialized receptor cells insense organs and internal organs.motor neuronType of neuron that signals muscles to relaxor contract.interneuronType of neuron that communicates informationfrom one neuron to the next.glial cells(GLEE-ull) Support cells that assist neuronsby providing structural support, nutrition,and removal of cell wastes; manufacturemyelin.Glial Cells: More than Glue Thiscolored micrograph shows one type ofglial cell, an astrocyte (green),enveloping a neuron (red). Astrocytesprovide connections between neuronsand blood vessels in the brain. Otherglial cells form the myelin sheath, afatty insulating substance that iswrapped around the parts of some,but not all, neurons. Another type ofglial cell removes waste products fromthe nervous system, including deadand damaged neurons. Beyond thosefunctions, researchers now know thatglia are much more actively involved inregulating neuronal communicationand activity than previously thought(Allen & Barres, 2009; Gibbs & others,2008).