Fundamentals of Anatomy and Physiology

The Nervous System: The Brain, Cranial Nerves, Autonomic Nervous System, and the Special Senses 269

Common Disease, Disorder, or Condition

DISORDERS OF THE NERVOUS SYSTEM continued

older. Symptoms worsen dramatically in individuals older than 70. Symptoms in-clude

memory failure, confusion, a decrease in intellectual capacity, restlessness, dis-

orientation, and, occasionally, speech disturbances. The disease produces a loss of

neurons in the cerebral cortex of the brain, resulting in a decrease in brain size. The

sulci widen and the gyri become narrowed. The temporal and frontal lobes of the

cerebrum are particularly affected. Enlarged axons containing beta-amyloid pro-tein,

called plaques, form in the cortex. There is a genetic predisposition for the dis-ease.

The first symptoms of the disease usually begin with an inability to assimilate new

information despite the ability to retain old knowledge, difficulty in recalling words, and a

disorientation in common surroundings. Death usually occurs 8 to 12 years after the

onset of symptoms. These patients should be kept comfortable and carefully observed

to keep them from self-harm.

Cerebrovascular Accident^
Cerebrovascular (seh-REE-bro-VAS-kyoo-lar) accident (CVA) or stroke can be
caused by a clot or thrombus in a blood vessel, or by a piece of a clot or embolus that
breaks loose and travels in the circulatory system until it lodges in a blood vessel and
blocks circulation. It can also be caused by a hemorrhage in tissue or by the constriction
of a cerebral blood vessel, known as a vasospasm. These situations can result in
localized cellular death due to lack of blood supply to the tissue. This is known as an
infarct. Symptoms are determined by the size and location of the infarct but can include
pa-ralysis or lack of feeling on the side of the body opposite the cerebral infarct, weak-
ness, speech defects, or the inability to speak. Death may result. However, symptoms
may subside in minor strokes when the resulting brain swelling subsides.

Meningitis^
Meningitis (men-in-JYE-tis) is an inflammation of the meninges caused by bacterial or
viral infection, which results in headache, fever, and a stiff neck. Severe cases of viral
meningitis can result in paralysis, coma, and death.

Encephalitis^
Encephalitis (in-seff-ah-LYE-tis) is an inflammation of brain tissue usually caused by a
virus transmitted by the bite of a mosquito. It is manifested by a wide variety of
symptoms, including coma, fever, and convulsions and could result in death.

Tetanus^
Tetanus is caused by the introduction of the bacterium Clostridium tetani into an open
wound. The bacterium produces a neurotoxin that affects motor neurons in the spinal
cord and brainstem. It also blocks inhibitory neurotransmitters, resulting in muscle
contractions. The jaw muscles are affected earliest, locking the jaw in a closed position,
hence the common name lockjaw. Death can result from spasms of the respiratory
muscles and the diaphragm.

Parkinson’s Disease^
Parkinson’s disease is characterized by tremors of the hand when resting and a slow
shuffling walk with rigidity of muscular movements. It is caused by damage to basal
nuclei, resulting in deficient dopamine, an inhibitory neurotransmitter. The disease can
be treated to a certain degree with L-dopa. New research uses the transplanting