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Chapter 3

PSY290 Chapter 3.docx

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Junchul Kim

Chapter 3 Anatomy of the Nervous System 3.1 General Layout of the Nervous System  Divisions of the Nervous System  Central Nervous System: Division of the nervous system that is located within the skull and spine  Peripheral Nervous System: Division that is located outside the skull and spine  Central Nervous System is divided into two divisions: brain (located in the skull) and spinal cord (located in the spine)  Peripheral Nervous System is divided into two divisions: the somatic nervous system (SNS) and the autonomic nervous system (ANS)  Somatic Nervous System is the part of the PNS that interacts with the external environment  SNS is composed of afferent nerves (which carry sensory signals) and efferent nerves (which carry motor signals from the central nervous system to the skeletal muscles)  Autonomic nervous system: the part of the peripheral nervous system that regulates the body’s internal environment  ANS is also composed of afferent nerves and efferent nerves  There are 2 kinds of efferent nerves: sympathetic nerves and parasympathetic nerves  Sympathetic nerves: the autonomic motor nerves that project from the CNS in the lumbar and thoracic regions of the spinal cord  Parasympathetic nerves: the autonomic motor nerves that project from the brain and sacral region of the spinal cord  3 principles of sympathetic nerves and parasympathetic nerves 1. Sympathetic nerves stimulate, organize, and mobilize energy resources in threatening situations, whereas parasympathetic nerves act to conserve energy 2. Autonomic target organ receives opposing sympathetic and parasympathetic input, and its activity is thus controlled by relative levels of sympathetic and parasympathetic activity 3. Sympathetic changes are indicative of psychological arousal, whereas parasympathetic changes are indicative of psychological relaxation  Most of the nerves of the peripheral nervous system project from the spinal cord, but there are 12 pairs of exceptions: cranial nerves  Cranial nerves: numbered in sequence from front to back, included purely sensory nerves and motor fibers  The autonomic motor fibers of cranial nerves are parasympathetic  Neurologists commonly assess cranial nerves as a basis for diagnosis, because their functions are specific.  Meninges, Ventricles, and Cerebrospinal Fluid  3 Meninges that are in bone covered the cortices: Dura mater (outer meninx), Arachnoid membrane (spider web like membrane) and pia mater (delicate, inner meninx that adheres of the surface of cortices)  In the subarachnoid space, the central canal of the spinal cord, and the cerebral ventricles of the brain, they are filled with cerebrospinal fluid (CSF)  Central Canal: small central channel that runs the length of the spinal cord  Cerebral Ventricles: the four large internal chambers of the brain; the 2 rd th lateral ventricles, the 3 ventricle, and the 4 ventricle  Cerebrospinal fluid supports and cushions the brain  Choroid Plexuses: the networks of capillaries that produce CSF  Blood-Brain Barrier  The cells of the blood vessel walls are tightly packed, which forms a barrier to the passage of many molecules  So many therapeutic or recreational drugs are penetrated the blood-brain barrier in order to influence the functions of the brain  Some big molecules, such as glucose, can pass through the barrier though 3.2 Cells of the Nervous System  Anatomy of Neurons  External Anatomy of Neurons  Internal Anatomy of Neurons  Neuron Cell Membrane  The neuron cell membrane is composed of a lipid bilayer  Classes of Neurons  4 kinds: 1. Multipolar Neuron 2. Unipolar Neuron 3. Bipolar Neuron 4. Interneurons: with a short axon or no axon at all; its function is to integrate the neural activity within a single brain structure, not to conduct signals from one structure to another  Neurons and Neuronanatomical Structure  Nuclei: the clusters of cell bodies in CNS;  Ganglia: the clusters of cell bodies in PNS  Tracts: Bundles of axons in CNS;  Nerves: Bundles of axons in PNS  Glial Cells: The Forgotten Cells  Glia cells: They can be found throughout the nervous systems, too  Oligodendrocytes: Glia cells with extensions that wrap around the axons of some neurons of the CNS  Myelin: a fatty insulating substance  Myelin Sheaths: formed by myelin, which increase the speed and efficiency of axonal conduction  Schwann Cells: Similar cells to oligodendrocytes in PNS, a second class of glial cells rd  Microglia: 3 class of glia cells; they respond to injury or disease by multiplying, engulfing cellular debris, and triggering inflammatory responses  Astrocytes: 4 class of glia cells; star-shaped, biggest glia cell, which cover the outer surfaces of blood vessels that course through the brain, and their function is to allow some chemicals from the blood into CNS and block some other chemicals  Astrocyte provides neurons nutrition, clearing waste, and forming a physical matrix to hold neural circuits together; in recent findings, they also send and receive signals to control and establish the maintances of synapses between neurons 3.3 Neuroanatomical Techniques and Directions  Neuroanatomical Techniques  Golgi Stain  Nissl Stain  Electron Microscopy  Neuroanatomical Tracing Techniques  Anterograde Tracing: It’s used when an investigator wants to trace the paths of axons projecting away from cell bodies located in a particular area; the investigators would inject chemicals that are taken up by cell bodies
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