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Download The Nervous System: Overview The nervous system Divisions of the
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12/01/2011 The nervous system Responsible for: Detecting changes in the internal and external The Nervous System: Overview environments Relaying messages to the endocrine system Relaying messages to the musculoskeletal system e ay g essages to t e uscu os e eta syste Section 9.1 Section 91 Page 412 Divisions of the nervous system Cognitive processes Perception Divisions of the nervous system Two main divisions: 1. Central nervous system (CNS): The brain & spinal cord NERVOUS SYSTEM 2. Peripheral nervous system (PNS): All of the other parts of the nervous system of the nervous system central nervous system (CNS) Somatic Autonomic peripheral nervous system (PNS) somatic nerves autonomic nerves control muscles, bones, and skin control internal organs of the body The peripheral nervous system Nerve cells The somatic nervous system is associated with conscious processes, and contains two types of neuron: Motor neurons Sensory neurons Two different types of cells make up nerve tissue: The autonomic nervous system is associated with unconscious processes, and has two divisions: Sympathetic Parasympathetic 1. Glial cells (support cells) 2. Neurons (functional cells): ( ) Sensory neurons – Relay environmental information to the CNS for processing Interneurons – Link neurons within the body; all neurons within the CNS are interneurons Motor neurons – Relay instructions to muscles, organs, and glands, in order to produce responses 1 12/01/2011 Neuron: Anatomy Receive information from other nerve cells; Conduct nerve impulses towards the cell bodies Conduction of nerve impulses Neurons conduct electrochemical messages from one neuron to the next. Contain the nucleus, cytoplasm, organelles y p , g The gap between neurons is called a synapse. Extension of cytoplasm, originating from the cell body; Project nerve impulses away from the cell body, towards other nerve cells Synapse Neuron: Anatomy (2) First neuron = Myelin sheath presynaptic neuron (fatty protein) Insulation Formed by Schwann p g cells)) cells ((special glial Second neuron = postsynaptic neuron postsynaptic neuron Nodes of Ranvier Increase speed of transmission Speed of impulses White matter vs. Grey matter Factors: White matter is myelinated Myelination Grey matter is not Diameter of axon (smaller = faster) 2 12/01/2011 Arrangement of nerve cells Neural circuits Nerve cells sometimes meet in bundles called ganglia Typical neural circuit: sensory receptor spinal cord brain spinal cord motor neurons (singular ganglion) Near the spine (dorsal root ganglia) Chain of ganglia, parallel to the spine (autonomic ganglia) Reflex arc: R fl sensory receptor spinal cord motor neurons Allows communication between central and peripheral nervous systems Reflex arcs Much faster than typical neural circuits Allows quick response to environmental stimuli 3