6.2 Peripheral Nervous System

Question 1

What is a plexus?

Answer 1

A network of intersecting nerve fibers; combines ventral rami of sequential spinal nerves

Question 2

What does a nerve consists of?

Answer 2

A bundle of nerve fibers outside the CNS

Question 3

What are the 3 layers covering a nerve bundle?

Answer 3

Endoneurium, Perineurium, and Epineurium

Question 4

Define Nerve fibers

Answer 4

The axon of a neuron. A nerve is formed of a bundle of many such fibers, with their sheaths.

Question 5

Define Peripheral Nervous System

Answer 5

The PNS consists of nerve fibers and cell bodies outside the CNS that conduct impulses to or aways from the CNS. The PNS is organized into nerves that connect the CNS with peripheral structures.

Question 6

Why is there a discrepancy between the number of cervical vertebrae and cervical spinal nerves?

Answer 6

Only 7 cervical vertebras but 8 cervical spinal nerves.
This is due to each cervical nerve running over the superior side of each cervical vertebra. This is opposite of the rest of the vertebra that travel inferior to the corresponding vertebra. Thus this allows for 8 cervical spinal nerves for 7 cervical spine

Question 7

What indicates the use of an Ankle Foot Orthosis?

Answer 7

Symptoms of a perineal nerve injury (foot drop) may include:

1) Inability to point toes toward the body. (dorsi flexion)
2) Pain
3) Weakness
4) Numbness (on shin or top of the foot)
5) Loss of function of the foot
6) High stepping walk (called stoppage gait or foot drop gait)

Question 8

What is an Ankle foot orthosis?

Answer 8

• Brace that is designed to be worn with appropriate footwear.
• Maintains ankle in a neutral position (90 degrees)
• Assistas patient with more normal gait.

Question 9

What peripheral nerve injury would necessitate the use of an Ankle Foot Orthosis?

Answer 9

Peroneal nerve injury

Question 10

What is meralgia paresthetica?

Answer 10

• It is a condition characterized by tingling, numbness, and burning in the outer thigh.
• No motor loss
• Usually self resolving

Question 11

What nerve is involved with meralgia paresthetica?

Answer 11

It is caused by the entrapment of the cutaneous nerve origination from the lumbar plexus.

Question 12

What is a Burner (stinger) injury?

Answer 12

• Traction or compression injury of the C5 &/or C6 ventral rami
• Motor and sensory involvement
• Usually transient (hours to weeks)

Question 13

What plexus is involved with the Burner injury?

Answer 13

The brachial plexus

Question 14

Define the Brachial Plexus

Answer 14

• A network of intersecting nerve fibers.
• Combines ventral rami of sequential spinal nerves.
• A peripheral nerve can have contribution from a number of spinal nerves