Chapter 12

Front 1

A typical spinal cord has how may pairs of spinal nerves, and where does the spinal cord end?

Back 1

A typical spinal cord has 31 pairs of nerves, and the spinal cord ends at the level of lumbar vertebra 1 or 2 (L1 or L2)

Front 2

Describe the composition of the gray matter of the spinal cord.

Back 2

The gray matter in the spinal cord is composed of the cell body of neurons, neuroglia, and unmyelinated axons.

Front 3

Describe the gross anatomical features of a cross section of spinal cord.

Back 3

Gross anatomical features of the cross-sectioned spinal cord include the anterior median fissure (a deep groove along the anterior or ventral surface); the posterior median sulcus (a shallow longitudinal groove); white matter( composed of myelinated and unmyelinated axons); gray matter (composed of cell bodies of neurons, neuroglia, and unmyelinated axons); the central canal (a passageway containing cerebrospinal fluid); a dorsal root of each spinal nerve (axons of neurons whose cell bodies are in the dorsal root ganglion); a ventral root of each spinal nerve (the axons of motor neurons that extend into the periphery to control somatic and visceral effectors); dorsal root ganglia (contain cell bodies of sensory neurons); and spinal nerves (containing the axons of sensory and motor neurons).

Front 4

Identify and describe the three spinal meninges.

Back 4

The three spinal meninges are the dura mater (the outermost component of the cranial and spinal meninges), arachnoid mater (the middle meninx that encloses cerebrospinal fluid), and pia mater (the innermost layer of the meninges bound to the underlying neural tissue).

Front 5

Where is the cerebrospinal fluid that surrounds the spinal cord located?

Back 5

Cerebrospinal fluid is found in the subarachnoid space, which lies beneath the epithelium of the arachnoid mater and superficial to the pia mater.

Front 6

Name the structures and spinal coverings that would be penetrated during lumbar puncture procedures.

Back 6

The lumbar puncture needle would penetrate the epidermis, dermis, subcutaneous layer (hypodermis), and then skeletal muscle before reaching the protective spinal coverings: dura mater, then the arachnoid matter, and finally the subarachnoid space, which contains cerebrospinal fluid.

Front 7

Differentiate between sensory nuclei and motor nuclei.

Back 7

Sensory nuclei receive and relay sensory information from peripheral receptors; motor nuclei issue motor commands to peripheral effectors.

Front 8

A person with polio has lost the use of his leg muscles. in which area of his spinal cord would you expect the virus-infected motor neuron to be?

Back 8

The poliovirus-infected neurons would be in the anterior gray horns of the spinal cord, where the cell bodies of somatic motor neurons are located.

Front 9

A disease that damages myelin sheaths would affect which portion of the spinal cord?

Back 9

A disease that damages myelin sheaths would affect the white matter columns of the spinal cord, which are composed of bundles of myelinated axons.

Front 10

Identify the three layers of connective tissue of a spinal nerve and identify the major peripheral branches of a spinal nerve.

Back 10

The three layers of connective tissue of a spinal nerve are the outer epineurium, middle perineurium, and inner endoneurium; and the major peripheral branches of a spinal nerve are the dorsal root and ventral root.

Front 11

Describe a dermatome.

Back 11

A dermatome is a specific bilateral sensory region monitored by a single pair of spinal nerves.

Front 12

Explain the etiology (cause) of shingles.

Back 12

Shingles is caused by a reactivation of the varicella-zoster virus (VZV), the same herpes virus that causes chickenpox. Once reactivated, the virus stimulates painful inflammation of the nerve ganglia and causes skin eruptions in a pattern that reflects the affected dermatome.

Front 13

Define gray ramus and white ramus.

Back 13

The gray ramus is a bundle of postganglionic sympathetic nerve fibers that are distributed to effectors in the body wall, skin, and limbs by way of spinal nerve; the white ramus is a nerve bundle containing the myelinated preganglionic axons of sympathetic motor neurons en route to sympathetic ganglia.

Front 14

Indicate whether the following fibers make up the white rami or gray rami:
1) Preganglionic fibers connecting a spinal nerve with a sympathetic ganglion in the thoracic and lumbar region of the spinal cord.
2) postganglionic fibers connecting a sympathetic ganglion in the thoracic or lumbar region with the spinal nerve.

Back 14

1) = White rami
2) = Gray rami

Front 15

Which ramus innervates the skin and muscles of the back?

Back 15

The dorsal ramus of each thoracic or superior lumbar spinal nerve innervates the skin and muscles of the back.

Front 16

Define nerve plexus, and list the major nerve plexuses.

Back 16

A nerve plexus is a complex, interwoven network of nerves. The major plexuses are the cervical, brachial, lumbar, and sacral plexuses.

Front 17

An anesthetic blocks the function of the dorsal rami of the cervical spinal nerves. Which areas of the body will be affected?

Back 17

An anesthetic that blocks the function of the dorsal rami of the cervical spinal nerves would affect the skin and muscles of the back of the neck and of the shoulders.

Front 18

Injury to which of the nerve plexuses would interfere with the ability to breathe?

Back 18

Damage to the cervical plexus-more specifically, to the phrenic nerves, which originate in this plexus and innervate the diaphragm-would interfere with the ability to breathe.

Front 19

Define a nerve plexus trunk or cord.

Back 19

A trunk is a large bundle of axons contributed by several spinal nerves; a cord is a smaller branch of nerves that originates at a trunk.

Front 20

Describe the brachial plexus.

Back 20

The brachial plexus is a network of nerves formed by branches of spinal nerve segments C4-T1, en route to innervating the upper limb.

Front 21

Name the major nerves associated with the brachial plexus.

Back 21

The major nerves associated with the brachial plexus are the dorsal scapular, long thoracic, suprascapular, medial and lateral pectoral, subscapular, thoracodorsal, axillary, medial antebrachial cutaneous, radial, musculocutaneous, median, and ulnar nerves.

Front 22

Describe the lumbar plexus and sacral plexus.

Back 22

The lumbar plexus is a nerve network formed by axons from the ventral rami of spinal nerve segments T12-L4; the sacral plexus is a nerve network formed by the ventral rami of spinal nerve segments L4-S4.

Front 23

List the major nerves of the sacral plexus.

Back 23

The major nerves of the sacral plexus are the superior and inferior gluteal nerves; the posterior femoral cutaneous nerve; the sciatic nerve, and the pudendal nerve.

Front 24

Compression of which nerve produces the sensation that your lower limb has "fallen asleep"?

Back 24

Compression of the sciatic nerve produces the sensation that your lower limb has "fallen asleep".

Front 25

Define reflex and list the components of a reflex arc.

Back 25

A reflex is a rapid, automatic response to a specific stimulus. All reflex arcs include a receptor, a sensory neuron, a motor neuron, and a peripheral effector; interneurons may or may not be present as well.

Front 26

What are common characteristics of reflexes?

Back 26

All reflexes are rapid, unconscious patterned responses to a physical stimulus, which restore or maintain homeostasis.

Front 27

Describe the various classifications of reflexes.

Back 27

Reflexes are classified according to their development (innate reflexes vs. acquired reflexes), the nature of the resulting motor response (somatic reflexes vs. visceral reflexes), the complexity of the neural circuit involved (postsynaptic reflexes vs. monosynaptic reflexes), and the site of information processing (spinal reflexes vs. cranial reflexes).

Front 28

Define stretch reflex.

Back 28

A stretch reflex is a monosynaptic reflex that provides automatic regulation of skeletal muscle length.

Front 29

In the patellar reflex, identify the response observed and the effectors involved.

Back 29

In the patellar reflex, the response observed is leg extension, and the effectors involved are the quadriceps femoris muscles.

Front 30

In the patellar reflex, in what way does stimulation of the muscle spindle by gamma motor neurons affect the speed of the reflex?

Back 30

When stretch receptors are stimulated by gamma motor neurons, the muscle spindles become more sensitive. As a result, little (if any) stretching stimulus is needed to stimulate the contraction of the quadriceps muscles. Thus, the reflex response would occur more quickly.

Front 31

Identify the basic characteristics of polysynaptic reflexes.

Back 31

All polysynaptic reflexes involve pools of interneurons, are intersegmental in distribution, involve reciprocal inhibition, and have reverberating circuits.

Front 32

Describe the flexor reflex.

Back 32

The flexor reflex is an example of a withdrawal reflex that contracts the flexor muscles of a limb in response to a painful stimulus; hence, it has a protective function.

Front 33

During a withdrawal reflex of the foot, what happens to the limb of the side opposite the stimulus? What is this response called?

Back 33

During a withdrawal reflex, the limb on the opposite, side is extended. This response is called a crossed extensor reflex.

Front 34

Define reinforcement as it pertains to spinal reflexes.

Back 34

Reinforcement is an enhancement of a spinal reflex through the facilitation of motor neurons involved in reflexes.

Front 35

What purpose does reflex testing serve?

Back 35

Reflex testing provides information about the nervous system's functional status.

Front 36

After injuring her back, 22-year-old Tina exhibits a positive Babinski reflex. What does this imply about her injury?

Back 36

A positive Babinski reflex is abnormal in adults; it indicates possible damage of descending tracts in the spinal cord.