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Chapter 3 Notes Notes on chapter 3 in point form

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Eileen Wood

Psychology Chapter 3 Yen HoangCommunication in the Nervous SystemNervous tissue the basic hardwareCells in the nervous system fall into two major categories glia and neurons o Neurons individual cells in the nervous system that receive integrate and transmit informationBasic links that permit communication within the nervous systemVast majority of them communicate only with other neuronsA small minority receive signals from outside the nervous system from sensory organs or carry messages from the nervous system to the muscles that move the bodyThere is no one single drawing of a neuron theres many varieties of types and shapesParts of the neuronSoma cell body contains the cell nucleus and much of the chemical machinery common to most cells o The rest of the neuron is devoted exclusively to handling informationDendrites are parts of a neuron that are specialized to receive information o They are branch like structures o Most neurons receive information from many other cells sometimes thousands of others therefore more extensive dendritic treesAxon is a long thin fibre that transmits signals away from the soma to other neurons or to muscles or glands o They may be quite long and they may branch off to communicate with a number of other cellsMyelin sheath is insulating material derived from glial cells that encases some axons o It speeds up the transmission of signals that move along axons o If an axons myelin sheath deteriorates its signals may not be transmitted effectivelyTerminal buttons are small knobs that secrete chemicals called neurotransmitters o Theyre at the end of axons o These chemicals serve as messengers that may activate neighbouring neuronsSynapse is a junction where information is transmitted from one neuron to another o ie the parts at which neurons interconnectIn summary information is received at the dendrites passed through the soma and along the axon and is transmitted to the dendrites of other cells at meeting points called synapses Types of neurons afferent sensory and efferent motorAfferent sensory relay information from the senses of the brain and spinal cordEfferent motor sends information from the central nervous system to the glands and muscles enabling the body to move o Glia are cells found throughout the nervous system that provide various types of support for neuronsThey tend to be much smaller than neurons but they outnumber neurons by about 10 to 1Therefore they appear to account for over 50 of the brains volumeThey supply nourishment to neurons help remove neurons waste products and provide insulation around many axonsThe myelin sheaths that encase many axons are derived from special types of glial cellsThey also play a complicated role in orchestrating the development of the nervous system in the human embryoGlia may also send and receive chemical signals They may also play an important role in memory formationSome types of glia cells can detect neural impulses and send signals to other glial cellsThe Neural Impulse Using Energy to Send Information o The Neuron at Rest A Tiny Battery o The resting potential of a neuron is its stable negative charge when the cell is inactiveThe charge is about 70 millivolts o The Action Potential o An action potential is a very brief shift in a neurons electrical charge that travels along an axonAs long as the voltage of a neuron remains constant the cell is quiet and no messages are being sentWhen the neuron is stimulated channels in its cell membranes open where it briefly allows positively charged sodium ions to enterFor an instant the neurons charge is less negative or even positive creating an action potential o Ie shift in electrical chargeo The absolute refractory period is the minimum length of time after an action potential during which another action potential cannot beginAfter the firing of an action potential the channels in the cell membrane that opened to let the sodium in close up
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