Psych 3 - Anatomy of the Nervous System (51-74) Nervous...

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Anatomy of the Nervous System (51-74) Nervous System - The central nervous system (CHS) is the division of the nervous system that is located within the skull and spine. The peripheral nervous system (PNS) is the division that is located outside the skull and spine. The central nervous system is composed of the brain, which is the part that is located in the skull, and the spinal cord, which is the part that is located in the spine. The PNS is composed of the somatic nervous system (SNS), which interacts with the external environment, containing afferent nerves that carry sensory signals from the skin, skeletal muscles, joints, eyes, ears, and so on, to the central nervous system, and efferent nerves that carry motor signals from the CNS to the skeletal muscles. The PNS is also composed of the autonomic nervous system (ANS), which is part of the peripheral nervous system that regulates the body’s internal environment, containing afferent nerves that carry sensory signals from internal organs to the CNS, and efferent nerves that carry motor signals from the CNS to internal organs. - The ANS has two kinds of efferent nerves, sympathetic, those that project from the CNS in the lumbar and thoracic regions of the spinal cord, and parasympathetic, those that project from the brain and sacral region of the spine. The sympathetic and parasympathetic neurons that project from the CNS and go only part of the way to the target organs before they synapse on other neurons that carry the signals the rest of the way. Sympathetic neurons project from the CNS synapse on second-stage neurons at a substantial distance from their target organs, where as parasympathetic neurons that project from the CNS synapse near their target organs on very short second-stage neurons. - Generally sympathetic nerves stimulate, organize and mobilize energy resources in threatening situations, whereas parasympathetic nerves act to conserve energy, each autonomic target organ receives opposing sympathetic and parasympathetic activity, and 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, except for the 12 pairs of cranial nerves (purely sensory), which project from the brain. The autonomic motor fibers of the cranial nerves are parasympathetic. - The brain and spinal cord are the most protected organs in the body; they are encased in bone and covered by three protective membranes (the three meninges). The outer meninx is a tough membrane called the dura mater, inside this is the fine arachnoid membrane (spider-weblike membrane), beneath this is the subarachnoid space which contains many large blood vessels and cerebrospinal fluid, then comes the innermost meninx, the delicate pia mater which adheres to the surface of the CNS. Also protecting the CNS is the cerebrospinal fluid (CSF), which fills the subarachnoid space, the central canal of the spinal cord, and the cerebral ventricles of the brain. The
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Psych 3 - Anatomy of the Nervous System (51-74) Nervous...

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