Lecture10.nervous_system

Lecture10.nervous_system - Nervous Systems The human brain...

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Nervous Systems
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The human brain contains about 100 billion nerve cells, or neurons Each neuron may communicate with thousands of other neurons
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Functional magnetic resonance imaging is a technology that can reconstruct a three- dimensional map of brain activity Brain imaging and other methods reveal that groups of neurons function in specialized circuits dedicated to different tasks
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Nervous systems consist of circuits of neurons and supporting cells All animals except sponges have a nervous system What distinguishes nervous systems of different animal groups is how neurons are organized into circuits
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Organization of Nervous Systems The simplest animals with nervous systems, the cnidarians, have neurons arranged in nerve nets
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More complex animals contain nerve nets as well as nerves Bundles of fiberlike extension of neurons
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More complex behavior evolved with cephalization in bilaterally symmetrical organisms
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Planarians have a simple well defines central nervous system (CNS) Small brain and longitudinal nerve cords
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Annelids and arthropods More complicated brains Ventral nerve cords containing segmentally arranged clusters of neurons called ganglia Nerves that connect the CNS with the rest of the body make up the peripheral nervous system (PNS)
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the nervous system organization correlates with an animal’s lifestyle Sessile or slow moving mollusks Little or no cephalization Relatively simple sense organs Active predatory mollusks Large brains Large image-forming eyes Rapid nerve signaling
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Sea stars have a nerve net in each arm connected by radial nerves to a central nerve ring
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Vertebrate Nervous System CNS Brain and spinal cord PNS Nerves and ganglia
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Information Processing Nervous systems process information in three stages: sensory input, integration, and motor output
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Sensory neurons transmit information from sensors that detect external stimuli and internal conditions Sensory information is sent to the CNS, where interneurons integrate the information Motor output leaves the CNS via motor neurons , which communicate with effector cells
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Reflexes Relatively simple nerve circuits The three stages of information processing are illustrated in the knee-jerk reflex
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Neuron Structure Most of a neuron’s organelles are in the cell body Most neurons have dendrites highly branched extensions that receive signals from other neurons The axon is typically a much longer extension transmits signals to other cells at synapses Many axons are covered with a myelin sheath
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Axon hillock The region where the axon joins the cell body Regions where signals are generated An axon usually divides into several branches Each ends in a synaptic terminal
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Neurons have a wide variety of shapes that reflect input and output interactions
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Supporting Cells (Glia) Glia are essential for structural integrity of the
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This note was uploaded on 11/02/2010 for the course CHEM 51LA 56555 taught by Professor Guan during the Spring '10 term at UC Irvine.

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Lecture10.nervous_system - Nervous Systems The human brain...

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