Ch3_Bio_Psy_09_02_09

Ch3_Bio_Psy_09_02_09 - Chapter3.2 Neurons&Behaviors...

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Chapter 3.2 Neurons & Behaviors
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Nervous System Cells Neurons The cells that make up your nervous system are called neurons. Neurons and communication Unique type of cell that can receive and transmit information electrochemically. Sensory neurons carry information from sense organs to the central nervous system. Neurons in the central nervous system process that information, interpret it, and then send commands to muscles, glands, and organs. Best estimate ~ 100 billion neurons
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  Figure 3.18 Figure 3.18 Distribution of the estimated 100 billion neurons in the adult human central nervous system. (Based on data of R. W. Williams & Herrup, 1988)
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Nervous System Cells Glia Support the neurons in many ways. They provide insulation, and remove waste products and foreign bodies. They are 1/10th the size of the neurons, but about 10 times as numerous. Anatomy of a neuron Neurons have a variety of shapes, but they all have 3 basic parts. A cell body that contains the nucleus and most of the organelles. The dendrites , widely branching structures that receive transmissions from other neurons. The axon , a single, long, thin fiber with branches near its tip.
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  Figure 3.20  Figure 3.20 The generalized structure of a motor neuron shows the dendrites, the branching structures that receive transmissions from other neurons, and the axon, a single, long, thin, straight fiber with branches near its tip. Axons range in length from 1 millimeter to more than 1 meter and carry information to other cells. Inset: A photomicrograph of a neuron.
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Nervous System Cells Axons The function of the axon is to send the electrochemical message on to the next cell. Most axons transmit information to the dendrites or cell bodies of neighboring neurons. Many axons have a coating of myelin, which speeds up transmission.
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Nervous System Cells Nerve cell growth Neurons do not have a fixed anatomy. Researchers have discovered that neurons are constantly growing and losing branches to dendrites and axons. This growth seems to be related to new experiences and learning.
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Nervous System Cells Action potentials Axons convey information by a combination of electrical and chemical processes. This combination is called an action potential. An action potential is an excitation that travels along the axon at a constant strength regardless of the distance it must travel.
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Nervous System Cells Action potentials The all-or-none law An action potential is an all-or-nothing process – it’s either happening or not; there’s no “sort of” action potential. This allows the message to reach the brain at full strength, but does slow it down compared to regular electrical conduction.
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Nervous System Cells How an action potential works: An un-stimulated axon has resting potential. Resting potential is an electrical polarization across the membrane
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Ch3_Bio_Psy_09_02_09 - Chapter3.2 Neurons&Behaviors...

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