CHAPTER 18 NERVOUS SYSTEM Copyright 2003 by Mosby, Inc. All rights reserved.

Structure and Function The nervous system is divided into two major structures Central nervous system (CNS) Peripheral nervous system (PNS) The function of the nervous system is: To sense, interpret, and respond to internal and external environmental changes in order to maintain a steady state in the body’s homeostasis Copyright 2003 by Mosby, Inc. All rights reserved.

Figure 18-1 Divisions of the Nervous System Copyright 2003 by Mosby, Inc. All rights reserved.

Table 18-1 Functions of the Peripheral Nervous System Copyright 2003 by Mosby, Inc. All rights reserved.

The Autonomic Nervous System Sympathetic system The sympathetic nerves are stimulated in situations that require action like the fight-or-flight reaction Parasympathetic system The parasympathetic nervous system functions in response to normal everyday situations Copyright 2003 by Mosby, Inc. All rights reserved.

Copyright 2003 by Mosby, Inc. All rights reserved. Neurons A bundle of fibers that carries impulses Three main types of neurons Afferent Efferent Interneuron Each carries messages, or impulses, to and from the body’s organs Copyright 2003 by Mosby, Inc. All rights reserved.

Copyright 2003 by Mosby, Inc. All rights reserved. Figure 18-4 Neuron Copyright 2003 by Mosby, Inc. All rights reserved.

Copyright 2003 by Mosby, Inc. All rights reserved. Neuroglia Special nervous tissue cells that act as “glue” to support, bind, repair, and protect neurons Five major types Astrocyte cells Oligodendroglia Microglia Ependymal cells Neuroglia Copyright 2003 by Mosby, Inc. All rights reserved.

Copyright 2003 by Mosby, Inc. All rights reserved. Synapse Space between two neurons Impulses from one neuron are transmitted across the synapse to another neuron by a chemical called a neurotransmitter Two most common neurotransmitters Acetylcholine Norepinephrine Copyright 2003 by Mosby, Inc. All rights reserved.

Copyright 2003 by Mosby, Inc. All rights reserved. Brain Largest structure of the nervous system and one of the largest organs of the body The brain is covered by three layers of membranes called meninges Dura mater Arachnoid Pia mater Copyright 2003 by Mosby, Inc. All rights reserved.

Assessment Techniques Electroencephalography (EEG) Lumbar puncture Myelography Nerve conduction velocity Computed tomography (CT) Positron emission tomography (PET) Magnetic resonance imaging (MRI) Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System Alzheimer’s A form of senile dementia Cerebrovascular accident Commonly called a stroke or CVA, is caused by loss of oxygen to an area of the brain when a clot blocks a vessel or when a vessel breaks Down syndrome A genetic disorder caused by the presence of an extra chromosome Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Encephalitis An inflammation of the brain caused by a virus, bacteria, or chemical agent Guillain-Barré syndrome Also called infectious polyneuritis; it may appear shortly after a viral immunization or infection Headache The muscles around the occipital area of the brain constrict the blood flow to the area Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Migraine headaches Vascular headaches of unknown cause; the pain results from the narrowing of blood vessels in the brain Sinus headaches From the swelling of the membranes that line the sinus cavities Head injury Occurs when the brain impacts with the skull as a result of a blow or rapid movement Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Huntington’s chorea A degenerative neural disorder that affects brain tissues Hydrocephalus Occurs when more cerebrospinal fluid is produced than absorbed into the circulatory system; the excess fluid increases intracranial pressure and may enlarge the head Intracranial tumors Usually involve neuroglia, blood vessels, or membranes rather than neurons Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Meningitis A serious inflammation of the meninges caused by a bacterium, virus, or fungus Meningocele A birth defect that occurs when the membranes covering the brain or spinal cord protrude through a congenital defect in the skull or spinal column Multiple sclerosis From a defect in electrical transmission of the neurons caused by degeneration of the myelin sheath Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Neural tube defect Defect in the formation of the skull and spinal column Neurofibromatosis Caused by a defect in an autosomal dominant gene Parkinson’s disease Results from degeneration of certain brain cells Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Poliomyelitis Caused by a virus that spreads from the nose and throat to neural tissue Sciatica Cause is usually a rupture of an intervertebral disk and osteoarthritis, producing pressure on the nerve or other nerve injury Seizure Results from injury, infection, or epilepsy Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Spina bifida A birth defect involving a malformed spinal column resulting from neural tube defects Spinal cord injuries Trauma occurring in the cervical and lumbar area of the spinal column Transient ischemic attack (TIA) Caused by a decrease in blood to an area of the brain resulting from a small clot that temporarily lodges in a vessel Copyright 2003 by Mosby, Inc. All rights reserved.

Disorders of the Nervous System (continued) Trigeminal neuralgia A sudden intense, unpredictable pain on one side of the face caused by pressure on or deterioration of the trigeminal facial nerve Copyright 2003 by Mosby, Inc. All rights reserved.

Issues and Innovations • Memory research – Three components of memory: sensory memory, short-term memory, and long-term memory – Memories are retained differently and in different parts of the brain • Parkinson’s correction – Causes three functional changes: slowness of movement, tremor, and rigidity – Transplant of adrenal gland cells to stimulate growth of dopamine – Fetal tissue research Copyright 2003 by Mosby, Inc. All rights reserved.