Chapter 11
Fundamentals of the Nervous System and Nervous Tissue
427
5.
In the Netherlands a young man named Jan was admitted
to the emergency room. He and his friends had been to a
rave. His friends say he started twitching and having muscle
spasms which progressed until he was “stiff as a board.” On
examination, staff found a marked increase in muscle tone
and hyperreflexia involving facial and limb muscles. In his
pocket, he had unmarked dark yellow tablets with dark flecks.
Analysis of the tablets showed them to contain a mixture of
ecstasy and strychnine. Ecstasy would not cause this clinical
picture, but strychnine, which blocks glycine receptors, could.
Explain how.
thereby rendering the nervous system quiescent while surgery is
performed. What specific process do anesthetics impair, and how
does this interfere with nerve impulse transmission?
3.
When admitted to the emergency room, John was holding his
right hand, which had a deep puncture hole in its palm. He
explained that he had fallen on a nail while exploring a barn. John
was given an antitetanus shot to prevent neural complications.
Tetanus bacteria fester in deep, dark wounds, but how do their
toxins travel in neural tissue?
4.
Rochelle developed multiple sclerosis when she was 27. AFer
eight years she had lost a good portion of her ability to control
her skeletal muscles. How did this happen?
Related Clinical Terms
Neuroblastoma
(nu
0
ro-blas-to
9
mah;
oma
5
tumor) A malignant
tumor in children; arises from cells that retain a neuroblast-like
structure. ±ese tumors sometimes arise in the brain, but most
occur in the peripheral nervous system.
Neurologist
(nu-rol
9
o-jist) A medical specialist in the study of the
nervous system and its functions and disorders.
Neuropathy
(nu-rop
9
ah-the) Any disease of nervous tissue, but
particularly degenerative diseases of nerves.
Neuropharmacology
(nu
0
ro-far
0
mah-kol
9
o-je) Scientific study of the
effects of drugs on the nervous system.
Neurotoxin
Substance that is poisonous or destructive to nervous
tissue, e.g., botulinum and tetanus toxins.
Rabies
(
rabies
5
madness) A viral infection of the nervous system
transmitted by the bite of an infected mammal (such as a dog,
bat, or skunk). AFer entry, the virus travels via axonal transport
in peripheral nerve axons to the CNS, where it causes brain
inflammation, delirium, and death. A vaccine- and antibody-
based treatment is effective if given before symptoms appear.
Rabies in humans is very rare in the United States.
Shingles
(herpes zoster) Inflammation of virally infected sensory
neurons serving the skin. Caused by the varicella-zoster virus,
which causes chicken pox (generally during childhood); during
the initial infection the virus is transported from the skin lesions
to the sensory cell bodies in the sensory ganglia. Typically, the
immune system holds the virus in check. It remains dormant
until the immune system is weakened, oFen by stress. ±en viral
particles multiply, causing nerve pain (neuralgia), and travel
back to the skin, producing characteristic scaly blisters. ±is
rash is usually confined to one side of the body trunk. Attacks
last several weeks, alternating between periods of healing and
relapse. Seen mostly in those over 50 years old. Vaccination can
prevent occurrence and minimize pain.
AT T H E C L I N I C
11
Elaine Sawyer, 35, was on her way to
the local elementary school with her
three children when the accident on
Route 91 occurred. As Mrs. Sawyer
swerved to avoid the bus, the right rear corner of her minivan struck
the side of the bus, causing the minivan to tip over and slide on its
side. Her children were shaken but unhurt. Mrs. Sawyer, however,
suffered a severe head injury that caused post-traumatic seizures.
The drugs initially prescribed for her treatment were insufficient
to control these seizures. Her doctor additionally prescribed Valium
(diazepam), but suggested that she use it only for a month because
Valium induces tolerance (loses its effectiveness). After a month of
Valium treatment, Mrs. Sawyer no longer had seizures and gradually
reduced and eliminated her use of Valium. After being seizure-free
for another year, restrictions on her driver’s license were lifted.
1.
Seizures reflect uncontrolled electrical activity of groups of
neurons in the brain. Valium is described as a drug that can
“quiet the nerves,” which means that it inhibits the ability of
neurons to generate electrical signals. What are these electrical
signals called, and what is happening at the level of the cell
when they are generated?
2.
Valium enhances inhibitory postsynaptic potentials (IPSPs). What
is an IPSP? How does it affect action potential generation?
3.
Valium enhances the natural effects of the neurotransmitter
GABA [gamma (
g
)-aminobutyric acid]. What chemical class of
neurotransmitters does GABA belong to? What are some of the
other neurotransmitters that fall into this same class?
4.
Theoretically, there are a number of possible ways that a drug
such as Valium could act to enhance the action of GABA. What
are three such possibilities?
5.
Valium actually works postsynaptically to promote binding of
GABA to its receptor, thereby enhancing the influx of Cl
ions
into the postsynaptic cell (the natural effect produced by
GABA). Why would this effect reduce the likelihood that this
cell would be able to produce an electrical signal?
(Answers in Appendix H)
Case Study
Nervous System
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