26.
As CSF is produced by the choroid plexuses, it flows into all four ventricles. CSF
from the lateral ventricles flows into the third ventricle and then through the
cerebral aqueduct into the fourth ventricle. By passing through three small holes
in the roof of the fourth ventricle, CSF enters the subarachnoid space. From here,
the CSF is transported through the arachnoid villi into the venous sinuses.
27.
The peripheral nervous system is that portion of the nervous system which
generally provides commands for skeletal muscles and other striated muscles and
carries sensory information from the periphery of the body. A nerve is a collection
28.
The 12 pairs of nerves attached to the right and left sides of the brainstem are
called cranial nerves. Each such nerve is identified by a Roman numeral in order
from I to XII and an individual name. Attached to the sides of the spinal cord are
31 pairs of spinal nerves. For each, the region is designated by a letter; within
each region, a nerve pair is identified by an Arabic numeral. (para 11-14c)
29.
Like a tree, a typical spinal nerve has roots, a trunk, and branches (called rami).
Coming off of the posterior and anterior sides of the spinal cord are the posterior
and anterior roots of the spinal nerve. An enlargement on the posterior root is the
posterior root ganglion. A ganglion is a collection of neuron cell bodies, together,
outside the CNS. Laterally, the posterior and anterior roots of the spinal nerve join
to form the spinal nerve trunk. The spinal nerve trunk of each spinal nerve is
located in the corresponding intervertebral foramen of the vertebral column. As
the nerve trunk emerges laterally, it divides into the anterior and posterior rami.
30.
If it carries information from the periphery to the CNS, it is an afferent (sensory)
neuron. If it carries information from the CNS to a muscle or gland, it is an efferent
31.
An automatic reaction to a stimulus is referred to as a reflex. The pathway from
the receptor organ to the reacting muscle is called the reflex arc. (para 11-15c(1))
32.
The pathway of a general reflex arc involves a minimum of five structures. The
stimulus is received by a receptor organ. The information is transmitted to the
CNS by the afferent (sensory) neuron. Within the spinal cord, there is a special
neuron connecting the afferent neuron to the efferent neuron; this special
connecting neuron is called the interneuron (or internuncial neuron). Carrying the
appropriate command from the spinal cord to the reacting muscle is efferent
(motor) neuron. The reacting muscle is called the effector organ. (para 11-15c(2))
33.
The autonomic nervous system is that portion of the nervous system generally
concerned with commands for smooth muscle, cardiac muscle, and glands.
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