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Sympathetic
Sensory Innervation of the Heart
The heart
and other visceral organs are innervated by the classic sympathetic
and vagal autonomic motor neurons. The nerves that contain sympathetic
and vagal motor neurons also contain sensory neurons originating
from the viscera.
Some people
consider the autonomic nervous system to be a purely motor system,
despite the presence of the sensory neurons.
Langley, who
in one sense is the father of the autonomic nervous system because
he provided the initial descriptions, clearly believed that the
sensory fibers were an important component of the autonomic nervous
system. He suggested that these sensory neurons were involved
in autonomic reflex functions as well as visceral pain. He also
used the term "afferent sympathetic fibers" (for a review
of this issue, see Cervero and
Foreman, 1990).
Our own investigations
of these sensory neurons fully support Langley's view; hence,
we will refer to sympathetic and vagal afferents in the remainder
of this chapter.
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