Chapter 13
Spinal Cord, Spinal nerves, and Spinal reflexes
I. Introduction
A. Introduction
1. The central nervous system consists of the __________and spinal cord.
2. The __________ is the largest and most complex part of the nervous
system
3. The brain includes two cerebral hemispheres, the diencephalon, the
brainstem, and the _________________.
4. The brainstem connects the brain and spinal cord and allows twoway communication between them.
5. The spinal cord provides two-way communication between the
central nervous system and the peripheral nervous system.
6. The brain lies within the ___________ cavity of the skull and the
spinal cord occupies the vertebral canal.
7. Meninges are located between the bone and the soft tissues of the
nervous system and protect the ___________and spinal cord.
II. Meninges
A. The meninges have ________________ layers.
B. The outermost layer is the __________ mater and is composed of tough,
white, dense connective tissue.
C. Dural sinuses are channels in dura ___________.
D. Denticulate ligaments are bands of pia mater that attach spinal cord to
________ mater.
E. The epidural space is between the dural sheath and the bony walls and
contains ________________ vessels.
F. The arachnoid mater is thin, weblike membrane that lacks blood vessels and is
located between the dura and _________________ maters.
G. The subarachnoid space is between the arachnoid and pia maters and contains
a fluid called ___________________ fluid.
H. The pia mater is very thin and contains many nerves and __________vessels.
I. The pia matter is attached to the surfaces of the brain and ___________ cord.
III. Ventricles and Cerebrospinal Fluid
A. Introduction
1. Ventricles are interconnected cavities and are located within the
_________________ hemispheres and brain stem.
2. The ventricles are continuous with the _____________ canal of the
spinal cord and are filled with cerebrospinal fluid.
3. The largest ventricles are the lateral ventricles which are located in the
cerebral ___________________.
4. The ____________ ventricle is located in the midline of the brain
beneath the corpus callosum.
5. The fourth ventricle is located in the brainstem just in front of the
______________.
6. The cerebral _______________ is a connection between the third and
fourth ventricles.
7. The choroids plexus is specialized mass of capillaries and functions to
secrete ____________________ fluid.
8. Most of the cerebrospinal fluid arises in the ___________________
ventricles and circulates into the third ventricle, fourth ventricle, the
central canal of the spinal cord, and the subarachnoid space.
9. Cerebrospinal fluid is continuously absorbed into the ______________.
10. Arachnoid granulations are tiny, fingerlike structures that project from
the ________________ space into the dural sinuses.
11. Cerebrospinal fluid is different from blood in that it contains a greater
concentration of _____________ and lesser concentrations of glucose and
potassium.
12. The functions of cerebrospinal fluid are to help maintain a stable
ionic concentration in the_______________nervous system, and provide a
pathway to the blood for wastes.
13. Because cerebrospinal fluid completely surrounds the brain and spinal
cord, it protects them by ______________ forces that might otherwise jar
and damage them.
IV. Spinal Cord
A. Introduction
1. The spinal cord is continuous with the brain and extends through
downward through the vertebral ______________.
2. The spinal cord begins at the level of the _____________ magnum and
terminates near the intervertebral disc that separates the first and second
lumbar vertebrae.
B. Structure of the Spinal Cord
1. The spinal cord consists of thirty-one segments, each of which gives
rise to a pair of _________________ nerves.
2. The two enlargements of the spinal cord are the cervical enlargement
and the _________________ enlargement.
3. The __________________ enlargement supplies nerves to the upper
limbs.
4. The lumbar enlargement supplies nerves to the ______________ limbs.
5. The ______________ medullaris is the tapered end of the spinal cord.
6. The filum terminale is a thin cord of connective tissue that anchors the
spinal cord to the upper surface of the ___________ (the tail vertebra)
7. The ____________equina is a group of spinal nerves below the conus
medullaris.
8. Two grooves that extend the length of the spinal cord are the anterior
median fissure and a __________ median sulcus.
9. In a cross section of the spinal cord, white matter surrounds
__________matter.
10. Each side of the gray matter is divided into the following three horns:
posterior horn, anterior horn, and ______________ horn.
11. Motor neurons are located in the _________________ horns.
12. The _____________commissure is a horizontal bar of gray matter in
the middle of the spinal cord.
13. The central canal is a canal running through the center of the gray
commissure down the entire length of the spinal ___________.
14. Three regions of the white matter are posterior funiculi, anterior
funiculi, and lateral ______________.
15. Nerve tracts are groups of myelinated nerve fibers in the
__________nervous system.
C. Functions of the Spinal Cord
1. Reflex Arcs
a. Reflex arcs carry out ________________.
b. A reflex arc begins with a receptor at the dendritic end of the of
a _____________________ neuron.
c. Nerve impulses on the sensory neurons enter the CNS and
constitute ______________ or sensory limb of the reflex.
d. The CNS is a _______________center.
e. Afferent neurons or interneurons ultimately connect with motor
neurons, whose fibers pass outward from the CNS to effectors
___________
2. Reflex Behavior
a. ______________ are automatic, subconscious responses to
changes within or outside the body.
b. Reflexes function to maintain homeostasis by controlling many
involuntary processes such as heart rate, _____________ rate, etc.
c. The knee-jerk reflex is an example of a simple ___________
reflex because it only uses two neurons.
d. The knee-jerk reflex is initiated by striking the ____________
tendon.
e. When the tendon is struck, the _______________ muscle is
pulled.
f. When the muscle is pulled, _____________ receptors are
stimulated.
g. The receptors generate a nervous impulse that enters the spinal
cord on an axon; the axon synapses with a ___________ neuron.
h. The axon of the __________ neuron synapses with the
quadriceps muscle and the muscle responds by contracting.
i. The _________-jerk reflex helps maintain posture.
j. The __________ reflex occurs when a person touches something
painful.
k. In the withdrawal reflex, muscles on the affected side contract
and the flexor muscles on the unaffected side are ____________.
l. The extensor muscles on the unaffected side ___________,
helping to support the body weight that has been shifted.
m. A crossed extensor reflex is due to interneuron pathways
within the reflex center of the spinal cord that allow sensory
impulses arriving on one side of the cord to pass across to the other
side and produce an ______________ effect.
n. A __________________ reflex protects because it prevents or
limits tissue damage when a body part touches something
potentially harmful.
3. Ascending and Descending Tracts
a. Ascending tracts conduct sensory impulses to the
______________.
b. ______________ tracts conduct motor impulses away from the
brain.
c. The names that identify nerve tracts often reflect the origin and
________________ of the tract.
d. Four major ascending tracts of the spinal cord are fasciculus
gracilis, fasciculus cuneatus, spinothalamic tracts, and
spino_____________ tracts.
e. The fasciculus gracilis and _____________ cuneatus are
located in posterior funiculi.
f. The fibers of ________________ gracilis and fasciculus
cuneatus conduct sensory impulses associated with the senses of
touch, pressure, and body movement from skin, muscles, tendons,
and joints to the brain.
g. The spinothalamic tracts are located in lateral and
____________funiculi.
h. The lateral spinothalamic tracts conduct impulses from various
body regions to the brain and give rise to sensations of pain and
_________________.
i. The anterior spinothalamic tracts impulses are interpreted as
_____________ and pressure.
j. Spinocerebellar tracts are located in ____________funiculi.
k. Impulses on the spinocerebellar tracts originate in the muscles of
the lower limbs and trunk and travel to the _______________.
l. Three major descending tracts of the spinal cord are
_____________tracts, reticulospinal tracts, and reubrospinal tracts.
m. Corticospinal tracts are located in ______ and anterior funiculi.
n. The corticospinal tracts conduct motor impulses associated with
voluntary movements from the brain to ______________ muscles.
o. The pyramidal tracts are the cortico__________ tracts and the
extrapyramidal tracts are all other descending spinal tracts.
p. Reticulospinal tracts are located in lateral and __________
funiculi.
q. Motor impulses of the reticulospinal tracts control muscular
_______________and activity of sweat glands.
r. Rubrospinal tracts are located in _____ funiculi.
s. Rubrospinal tracts carry motor impulses that coordinate muscles
and control ___________.
Spinal Nerves
1. Introduction
a. There are thirty-one pairs of _____________ nerves.
b. All spinal nerves are mixed nerves and they provide two –way
communication between the spinal cord and parts of the upper and
lower limbs, neck and ______________.
c. There are 8 pairs of ____________ nerves.
d. There are __________ pairs of thoracic nerves.
e. There are 5 pairs of ______________ nerves.
f. There are 5 pairs of sacral _____________.
g. There is 1 pair of _____________ nerves.
h. The adult spinal cord ends at the level of the first or second
_____________ vertebrae.
i. The cauda equina is a collection of spinal nerves at the end of the
_____________ cord.
j. Each spinal nerve emerges from the spinal ___________ by
roots.
k. The ________root ganglion contains the cell bodies of the
sensory neurons whose dendrites conduct impulses from the
peripheral body parts.
l. The axons of neurons in __________ root ganglia extend
through the dorsal root.
m. A _____________ is an area of skin that the sensory nerve
fibers of a particular spinal nerve innervate.
n. The _____________ root consists of axons from the motor
neurons whose cell bodies are located within the gray matter of the
cord.
o. A ventral root and dorsal root unite to form a ______________
nerve.
p. A meningeal branch of a spinal nerve supplies the
_______________ and blood vessels of the spinal cord, as well as
the intervertebral ligaments and the vertebrae.
q. A posterior branch of a spinal nerve supplies the muscles and
skin of the ________.
r. An _____________ branch of a spinal nerve supplies muscles
and skin on the front and sides of the trunk and limbs.
s. A ____________ is a complex network of anterior branches of
spinal nerves.
t. In a plexus, fibers of various spinal nerves are sorted and
recombined, so fibers associated with a particular peripheral body
part reach it in the same nerve, even though the fibers originate
from different spinal nerves.
2. Cervical Plexuses
a. The _____________ plexus is located deep in the neck on either
side.
b. The cervical plexus is formed by the anterior branches of the
first four cervical nerves.
c. Fibers from the cervical plexus supply the muscles and skin of
the neck and contribute to the _________________ nerve.
d. The phrenic nerve conducts impulses to the
_________________.
3. Brachial Plexuses
a. The brachial plexus is located deep within the shoulders between
the ______________ and axillae.
b. The brachial plexus is formed by the anterior branches of the
lower four cervical nerves and the first _______________ nerve.
c. The major branches emerging from the brachial plexus are the
musculocutaneous, ulnar, median, ___________, and axillary.
d. The musculocutaneous nerves supply muscles of the arms on the
anterior sides and the ____________ of the forearms.
e. The ____________ nerves supply muscles of the forearms and
hands and the skin of the hands on the ulnar side
f. The__________ nerves supply muscles of the arms on the
posterior sides and the skin of the forearms and hands on the radial
side
g. The median nerves supply muscles of the forearms and muscles
and skin of the hands of the medial part of the forearm
h. The _____________ nerves supply muscles and skin of the
anterior, lateral, and posterior regions of the arm. (in the axillary
region)
4. Lumbosacral Plexuses
a. The lumbosacral plexus is located in the ___________and pelvic
regions.
b. The _________________ plexus is formed by anterior branches
of the last thoracic nerve and lumbar, sacral, and coccygeal nerves.
c. The major branches of the lumbosacral plexus are obturator,
femoral, and ________________ nerves.
d. The _____________ nerves supply the adductor muscles of the
thighs.
e. The _____________ nerves supply motor impulses to muscles
of the anterior thigh and receive sensory impulses from the skin of
the thighs and legs.
f. The sciatic nerves supply muscles and skin the thighs, legs, and
_____________.
g. The anterior branches of thoracic spinal nerves do not enter a
plexuses; instead these branches become ______________ nerves
that supply motor impulses to the intercostals muscles and the
upper abdominal wall muscles.