Chapter 13 The Peripheral Nervous System and Reflex Activity

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Chapter 13 The Peripheral Nervous System and Reflex Activity Matching exam, true / false exam, short answer exam, fill in the blank exam, Clinical question exam
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Using Figure 13.1, match the following:

1) Innervates the superior oblique muscle.

2) Longest cranial nerve.

3) Damage to this nerve would cause dizziness, nausea, and loss of balance.

4) Involved in movement of the digestive tract.

5) Damage to this nerve would cause difficulty in speech and swallowing, but no effect on
visceral organs.

6) Damage to this nerve would keep the eye from rotating inferolaterally.

Using Figure 13.1, match the following:

1) Answer: B

2) Answer: D

3) Answer: C

4) Answer: D

5) Answer: E

6) Answer: B


Using Figure 13.2,
identify the following components of the reflex arc:

7) Integration center.

8) Sensory neuron.

9) Effector.

10) Motor neuron.

11) Receptor.

Using Figure 13.2,
identify the following components of the reflex arc:

7) Answer: E

8) Answer: C

9) Answer: B

10) Answer: D

11) Answer: A


Match the following:

12) Formed by the union of a
cranial and a spinal root.

13) Receptors located in
epithelium of the nasal cavity.

14) Serves the senses of hearing
and equilibrium.

15) Helps to regulate blood
pressure and digestion.

16) Turns the eyeball laterally.

A) Vagus
B) Olfactory
C) Accessory
D) Abducens
E) Vestibulocochlear

12) C
13) B
14) E
15) A
16) D


Match the following reflexes to their function:

17) Tests both upper and lower
motor pathways. The sole of
the foot is stimulated with a
dull instrument.

18) Checks the integrity of the
spinal cord and dorsal rami at
the level of T8 to T12.

19) Produces a rapid withdrawal
of the body part from a
painful stimulus; ipsilateral.

20) Prevents muscle
overstretching and maintains
muscle tone.

A) Stretch
B) Abdominal
C) Flexor
D) Plantar

17) D
18) B
19) C
20) A


Match the following:

21) The obturator and femoral
nerves branch from this

22) Striking the ʺfunny boneʺ
(ulnar nerve) may cause
injury to a nerve of this

23) Trauma to a nerve of this
plexus may cause wrist drop.

24) A fall or improper
administration of an injection
to the buttocks may injure a
nerve of this plexus.

25) The phrenic nerve branches
from this plexus.

A) Lumbar plexus
B) Brachial plexus
C) Cervical plexus
D) Sacral plexus

21) A
22) B
23) B
24) D
25) C


Match the following:

26) Controls the outputs of the
cortex and regulates motor

27) Central pattern generators.
Diff: 1 Page Ref: 519; Fig. 13.13
28) Intermediate relay for
incoming and outgoing

29) The cerebellum and basal

30) Includes cortical and brain
stem motor areas.

31) The neural machinery of the
spinal cord, including spinal
cord circuits.

A) Projection level
B) Segmental level
C) Precommand level

26) C
27) B
28) A
29) C
30) A
31) B


True/False Questions

1) The meningeal branch of a spinal nerve actually reenters the vertebral canal to innervate the
meninges and blood vessels.

Answer: TRUE


2) In the somatosensory system there are no third-order neurons in the cerebellum.

Answer: TRUE


3) There are 41 pairs of spinal nerves.

Answer: FALSE


4) The glossopharyngeal nerve is the only cranial nerve that contains sensory fibers.

Answer: FALSE


5) The musculocutaneous nerve is a major nerve of the brachial plexus.

Answer: TRUE


6) The second cranial nerve forms a chiasma at the base of the brain for partial crossover of
neural fibers.

Answer: TRUE


7) The only cranial nerves to extend beyond the head and neck region are the vagus nerves.

Answer: TRUE


8) The dorsal ramus consists only of motor fibers bringing information to the spinal cord.

Answer: FALSE


9) Dermatomes are skin segments that relate to sensory innervation regions of the spinal nerves.

Answer: TRUE


10) Dorsal and ventral rami are similar in that they both contain sensory and motor fibers.

Answer: TRUE


11) Irritation of the phrenic nerve may cause diaphragm spasms called hiccups.

Answer: TRUE


12) The obturator nerve branches from the sacral plexus.

Answer: FALSE


13) Reciprocal inhibition means that while one sensory nerve is stimulated, another sensory
neuron for synergistic muscles in the same area is inhibited and cannot respond.

Answer: FALSE


14) External strabismus and ptosis could be caused by damage to the oculomotor nerve.

Answer: TRUE


15) In order to regulate motor activity, to start and stop movements, and to coordinate postural
movements, the cerebellum and basal nuclei are involved.

Answer: TRUE


Fill-in-the-Blank/Short Answer Questions

1) ________ law states that any nerve serving a muscle that produces movement at a joint also
innervates the joint itself and the skin over the joint.

Answer: Hiltonʹs


2) ________ are modified free-nerve endings found in the deeper levels of the epidermis.

Answer: Merkel discs


3) The perineurium defines the boundary of a ________.

Answer: fascicle


4) The ________ nerve is the largest of the cranial nerves.

Answer: trigeminal


5) Ventral spinal cord roots contain ________ fibers, while the dorsal roots contain ________

motor (efferent); sensory (afferent)


6) The facial nerve is cranial nerve number ________.

Answer: VII


7) ________ is a protective reflex that also overrides the spinal pathways and prevents any other reflexes from using them at the same time.

Answer: Flexor reflex


8) ________ is the tingling sensation or numbness when blood has been cut off from an area, as
when the foot ʺgoes to sleep.ʺ

Answer: Ischemia


9) Pain, temperature, and coarse touch are involved in the ________ ascending pathways of the
somatosensory system.

Answer: nonspecific


10) Complex motor behavior such as walking depends on ________ patterns.

Answer: fixed-action


11) Mr. Smith staggered home after a long night at the local pub. While attempting to navigate the
stairs, he passed out cold and lay all night with his right armpit straddling the staircase banister. When he awoke the next morning, he had a severe headache, but what bothered him
more was that he had no sensation in his right arm and hand. Explain what caused this
symptom in his arm.

Answer: Continuous pressure interrupts blood flow along with oxygen and nutrients to the
neuron processes. As a result, impulse transmission is inhibited temporarily.


12) Define Golgi tendon organs and muscle spindles relative to the stretch reflex.

Answer: Golgi tendon organs work with muscle spindles to act as proprioceptors in skeletal
muscles and their associated tendons. When muscles are stretched due to contraction of
antagonist muscles, the sensory neurons send impulses to the spinal cord, where they
synapse with motor neurons of the stretched muscle. Impulses are then sent to the
stretched muscle, which then resists further stretching. This prevents muscle tissue


13) Distinguish between monosynaptic and polysynaptic reflexes and between ipsilateral and
contralateral reflex responses.

Answer: Monosynaptic refers to a single synapse in the reflex arc (one sensory and one motor
neuron). Polysynaptic refers to more than one synapse in the arc involving sensory
neurons, interneurons, and motor neurons. Ipsilateral refers to a reflex arc limited to
one side of the spinal cord, while contralateral reflexes cross to the opposite side.


14) What is the normal response of the plantar reflex? What is Babinskiʹs sign and what does it

Answer: The plantar reflex tests the integrity of the spinal cord from L4 to S2 and also
determines if corticospinal tracts are functioning and properly myelinated. The normal
plantar response is downward flexion of the toes. If there is damage, the great toe
dorsiflexes and smaller toes fan laterally (Babinskiʹs sign). Infants, who normally lack
complete myelination, exhibit this sign.


15) List and describe the functions of the three cranial nerves that serve the muscles of the eye.

Answer: The three cranial nerves are: oculomotor, trochlear, and abducens. The oculomotor is
mostly motor, with branches to the inferior oblique and superior, inferior, and medial
rectus muscles, as well as to the muscles of the iris and lens. The trochlear supplies
mostly motor fibers to the superior oblique muscles of the eye. The abducens supplies
mostly motor fibers to the lateral rectus muscles of the eye. Like most motor nerves,
they also carry some sensory information for proprioception.


16) Name an exteroceptor that is not a cutaneous receptor and explain why.

Answer: Exteroceptors that are not cutaneous receptors include the chemoreceptors of the tongue
and nasal mucosa, the photoreceptors of the eyes, and the mechanoreceptors of the
inner ear. These all monitor changes in the external environment, so they are classified
as exteroceptors.


17) Speculate about the benefit of having the nerve supply of the diaphragm, which is located in
the thoracic-lumbar area of the spinal cord, arise from cervical nerves?

Answer: The fact that the phrenic nerve originates so high in the spinal cord reduces the
likelihood of spinal damage above the phrenic origin, thereby reducing the possibility
that a spinal injury would stop the diaphragm from working.


18) George, a 20-year-old man, injured his jaw and lost several teeth in a barroom brawl. Several
weeks later he began to experience sharp stabbing pain in his lower jaw. After visiting the
dentist, he was told that he had trigeminal neuralgia. What is this condition and how is it

Answer: Trigeminal neuralgia, or tic douloureux, is an inflammation of the trigeminal nerve,
probably caused by the fight and subsequent damage to the jaw.


19) How is a receptor potential similar to an excitatory postsynaptic potential (EPSP) generated at a synapse?

Answer: A receptor potential acts essentially the same as an EPSP in that stimulus causes
changes in permeability of the receptor membrane, which results in a graded potential.
It will increase or decrease depending on the intensity of the stimulus.


20) How does accommodation of muscle spindles figure in the importance of stretch routines as a
warm-up for exercise?

Answer: Initially, as muscle spindles are stretched, the reflex sends impulses back to contract the muscle. With prolonged stretching, accommodation decreases the vigor of the stretch
reflex somewhat, and the muscle can relax and stretch more, reducing the risk of tearing
muscle tissue during exercise.


21) Name three unencapsulated sensory receptors and tell what they are used for.

1. Free nerve endings are found throughout the body. They are used by most body tissues to determine stretching, joint positioning, etc. In the epidermis they become
pain receptors, heat and cold receptors, and possibly very light pressure receptors.

2. Modified free nerve endings called Merkel disks. They are used as light touch

3. Hair follicle receptors are mechanical receptors that become very fine touch


22) When we hear a strange sound in a room what perceptual level is activated?

Answer: The perceptual detection level is the only level acted upon. In some cases this alone
allows our imagination to go ʺwildʺ with possibilities.


23) What is Wallerian degeneration?

Answer: The complete degeneration of the distal end of an axon after it has been severed.


Clinical Questions

1) Ralph sustained a leg injury in a bowling accident and had to use crutches. Unfortunately, he
never took the time to learn how to use them properly. After two weeks of use, he noticed his
fingers were becoming numb. Then he noticed his arms were getting weaker and tingling.
What could be his problem?

Answer: Compression of the radial nerve (in the region of the armpit) may cause temporary
cessation of nervous transmission, often called ʺSaturday night paralysis.ʺ Continued
pressure could cause permanent damage.


2) A patient suffers nerve damage to the sciatic nerve, requiring surgery to suture the nerve back
together. After surgery, the patient reports that sensation from the lateral and medial sides of
the knee seem to be reversed. How could this happen?

Answer: In suturing the nerve back together, there is no guide to ensure that each nerve fiber
continues across the transection into the same neurilemma in which it started. Nerve
fibers can grow into pathways different from their original ones and establish new
synapses. The brain cannot keep track of which nerve fibers have grown into different
pathways, and projects sensations back to the point of origin.


3) David, an aspiring baseball player, was struck on the left side of his face with a fastball pitch.
He was not wearing a safety helmet. His zygomatic arch was crushed, as well as parts of the
temporal bone. Following the accident and reconstructive surgery, he noted that his left lower
eyelid was still drooping and the corner of his mouth sagged. What nerve damage did he

Answer: He suffered facial nerve damage on his left side. Due to the bone damage, branches to
the eye and jaw were probably damaged. It is possible that the damage could be
reversible if the nerves were not cut or crushed completely.


4) A nurse is asked about the cause of the excruciating pain of tic douloureux. How should s/he answer?

Answer: The excruciating pain is caused by inflammation of the trigeminal nerve. Pressure on
the trigeminal nerve root can turn normal stimuli like tooth brushing into painful


5) A patient received Morphine Sulfate, 10 mg IV, two hours ago for standard postoperative
pain. She is now crying and complaining of continued pain. Is this an example of pain
threshold or pain tolerance? Explain why.

Answer: This is an example of pain tolerance. Pain tolerance is the maximum amount and duration of pain that an individual is willing to tolerate. In this case the patient appears to have a low tolerance because she is crying and complaining of continued pain.


6) The patient is receiving transcutaneous electrical nerve stimulation (TENS) for back pain.
Describe how this may work based on the gate control theory.

Answer: According to this theory, small-diameter nerve fibers carry pain stimuli through a gate,
but larger diameter nerve fibers going through the same gate can inhibit the transmission of those pain impulses by closing the gate. The electrical stimulation of the skinʹs large touch fibers causes the gates to close, thereby inhibiting pain.


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