24. The two main pairs of arteries supply oxygenated blood to the brain are the
internal
and
arteries. Beneath the brain, branches of these
arteries join to form a circle, called the
circle (of
). The main
pair of veins carrying blood back toward the heart is the internal
veins.
The blood supply of the spinal cord is by way of a combination of three l___________
arteries running along its length and reinforced by s
arteries from the sides.
25. Found in the cavities of the CNS is a clear fluid called
fluid (
).
This fluid is found in the
s of the brain, the sub
space, and the
spinal cord's
canal. Special collections of arterial capillaries found in the roofs
of the third and fourth ventricles are called choroid
s. These structures
continuously produce CSF from the
of the blood.
26. As CSF is produced by the choroid plexuses, it flows into all four
s.
CSF from the lateral ventricles flows into the
ventricle, and then through the
aqueduct into the
ventricle. By passing through three small holes
in the roof of the fourth ventricle, CSF enters the subarachnoid
. From here,
the CSF is transported through the arachnoid
into the venous sinuses.
27. The peripheral nervous system is that portion of the nervous system which
generally provides commands for
muscles and other
muscles
and carries
y information from the p
of the body. A nerve is a
collection of neuron
s, together and
the CNS.
28. The 12 pairs of nerves attached to the right and left sides of the brainstem
are called
nerves. Each such nerve is identified by a
in order from
to
and an individual name. Attached to the sides of the spinal cord are 31
pairs of
nerves. For each, the region is designated by a
; within each
region, a nerve pair is identified by an
.
29. Like a tree, a typical spinal nerve has
s, a
, and branches (called
). Coming off of the posterior and anterior sides of the spinal cord are the
posterior and anterior
of the spinal nerve. An enlargement on the posterior root is
the
. A ganglion is a collection of
, together,
outside the CNS. Laterally, the posterior and anterior roots of the spinal nerve join to
form the spinal nerve
. The spinal nerve trunk of each spinal nerve is located in
the corresponding intervertebral
of the vertebral column. As the nerve trunk
emerges laterally, it divides into the anterior and posterior
.
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