1. CHAPTER 18 NERVOUS SYSTEM
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2. 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
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3. Figure 18-1 Divisions of the Nervous System
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4. Table 18-1 Functions of the Peripheral Nervous System
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5. 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
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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
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Figure 18-4 Neuron
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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
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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
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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
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11. Assessment Techniques
Electroencephalography (EEG)
Lumbar puncture
Myelography
Nerve conduction velocity
Computed tomography (CT)
Positron emission tomography (PET)
Magnetic resonance imaging (MRI)
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12. 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
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13. 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
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14. 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
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15. 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
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16. 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
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17. 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
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18. 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
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19. 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
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20. 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
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21. 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
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