Deck 12: Peripheral Nervous System

Question 1

Myasthenia gravis is an autoimmune disease affecting the:

A)Myelin of peripheral nerves.
B)ACh receptors at the neuromuscular junction.
C)Release of ACh from the presynaptic terminal.
D)Storage of calcium in the sarcoplasmic reticulum.
E)Alpha motor neurons in the ventral horn of spinal cord.

Answer 1

B
Explanation: Myasthenia gravis is an autoimmune disease that damages ACh receptors on the muscle membrane.

Question 2

The brachial plexus emerges from:

A)Between the anterior and middle scalene muscles
B)Between the posterior and middle scalene muscles
C)Psoas major muscle
D)Psoas minor muscle

Answer 2

A
Explanation: The brachial plexus is formed by anterior rami of C5-T1.The plexus emerges between the anterior and middle scalene muscles,passes deep to the clavicle,and enters the axilla.

Question 3

What does the lumbar plexus innervate?

A)Diaphragm
B)Medial leg and foot
C)Posterior thigh
D)None of the above

Answer 3

B
Explanation: The lumbar plexus is formed by the anterior rami of L1-L4;the plexus forms in the psoas major muscle.Branches of the lumbar plexus innervate skin and muscles of the anterior and medial thigh.A cutaneous branch from the plexus,the saphenous nerve,continues into the leg to innervate the medial leg and foot.Branches of the cervical,brachial,and lumbar plexuses provide sympathetic innervation via connections with the sympathetic chain.

Question 4

If NCV studies show that conduction is slowed at a single site in one nerve,yet the NCV is normal throughout the remainder of the nerve and in other nerves,the disorder is characterized as which of the following?

A)Traumatic myelinopathy
B)Axonopathy
C)Severance injury
D)Myopathy
E)Polyneuropathy

Question 5

Guillian-Barré syndrome is an autoimmune disease that causes:

A)Necrosis of the alpha motor neuron
B)Degeneration of the motor endplate
C)Spasticity
D)Peripheral demyelination
E)Degeneration of the C-fiber axons

Question 6

What occurs when a nerve is stretched past the capacity of the surrounding structures?

A)Tensile stress develops in the neural tissues.
B)Axons unfold.
C)The external epineurium stretches.
D)None of the above occurs.

Question 7

Which of the following characteristics distinguish central nervous system dysfunction from peripheral nervous system dysfunction?

A)Hypertonia in upper motor neuron involvement
B)Paraspinal sensation
C)Slow muscle atrophy
D)Hypertonia in lower motor neuron involvement

Question 8

What is the most functionally important branch of the cervical plexus?

A)Branch to the sternocleidomastoid muscle
B)Branch to the biceps brachii
C)Branch to the triceps
D)Phrenic nerve
E)Musculocutaneous nerve

Question 9

What is the most important branch of the cervical plexus?

A)Vagus nerve
B)Accessory nerve
C)Phrenic nerve
D)Mandibular nerve

Question 10

Miniature endplate potentials are essential for which of the following?

A)Inhibiting the action of lower motor neurons
B)Initiating contraction of muscles
C)Preventing atrophy of muscle fibers
D)A and B
E)All of the above

Question 11

Trophic changes after denervation include which of the following?

A)Muscle atrophy
B)Shiny skin
C)Brittleness of fingernails and toenails
D)A and B
E)All of the above

Question 12

What does the sacral plexus innervate?

A)Diaphragm
B)Medial leg and foot
C)Posterior thigh and most of the leg and foot
D)None of the above

Question 13

Which one of the plexes innervates the posterior thigh and most of the leg and foot?

A)Cervical
B)Brachial
C)Lumbar
D)Sacral
E)None of the above

Question 14

If the NCV is normal along the length of the peripheral nerve,yet the amplitude of the electromyogram (EMG)potential is decreased,the disorder is:

A)Myelinopathy
B)Myopathy
C)Lower motor neuron lesion
D)Upper motor neuron lesion
E)Axonopathy

Question 15

In a recording from a nerve conduction velocity (NCV)study,decreased amplitude of recorded potentials,combined with slowing of NCV,indicates which of the following?

A)Myelinopathy
B)Myopathy
C)Myasthenia gravis
D)Upper motor neuron lesion
E)Axonopathy