(2) Descending. The descending pathways carry stimuli for voluntary and
involuntary functions.
3-2.
PHARMACOLOGIC CONSIDERATIONS OF THE CNS
The CNS is more sensitive to the action of drugs than any other system in the
body. Drugs act on it either by stimulation or by depression. Stimulation may range
from mild alertness to convulsions; depression may range from mild sedation to loss of
consciousness. The parts of the CNS respond to the presence of drugs with specific
action. When given in ordinary doses, drugs may affect only one specific portion of the
CNS, but when they are given in larger doses, they may affect the entire system. The
following are examples of this:
a. Caffeine given in small doses stimulates the psychic center; given in larger
doses, it stimulates the respiratory center; and given in very large doses, it may induce
convulsions.
b. Alcohol depresses the inhibitory centers in the cerebral cortex; large doses
depress the medulla, causing a slowing of respiration, sometimes even to the point of
death.
c. Anesthetics depress sensory and motor areas of the cortex and the reflex
centers in the spinal cord. Given in large doses, they depress the respiratory center in
the medulla.
d. Phenobarbital depresses sensory and motor areas of the cortex; large doses
depress the respiratory center in the medulla.
e. Morphine gives relief from pain by acting primarily on sensory areas in the
cerebral cortex. Given in large doses, it causes respiratory depression.
Section II. SEDATIVE-HYPNOTICS
3-3.
EFFECTS OF SEDATIVE-HYPNOTICS
A hypnotic, also called a soporific or somnifacient, is an agent that induces
sleep. A sedative is an agent that produces relaxation, lessens excitement, and slows
motor activity. However, a drug that falls into one of these categories generally falls
into the other also and is thus called a sedative-hypnotic. The effect of a sedative-
hypnotic depends on the dose. A small dose produces sedation; a large dose produces
sleep. However, because of differences in duration of action, some of these drugs are
preferable for use as hypnotics and others as sedatives. The effects that sedative-
hypnotics produce depend to some extent on the traits of the particular client, but we
can still give a description of the effects generally to be expected. Sedative-hypnotics
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