Peripheral nervous system lecture

Question 1

Read through the glossary of the peripheral nervous system

Answer 1

• Anterior ramus (ventral branch) – anterior division of spinal nerve
• Plexus (Latin for “braid”) – branching network of nerves/vessels
• Ganglion – nerve cell cluster/group of nerve bodies in the autonomic nervous system/sensory system
• Afferent – input nerve fibres (receive information)
• Efferent – output nerve fibres (motor supply)
• Dura – thick outer meningeal layer attached to skull
• Arachnoid – layer containing arachnoid spaces/blood brain barrier for exchange between blood and cerebrospinal fluid (CSF)
• Pia – protective layer directly over the brain and continues down spinal cord.
• White ramus communicans - preganglionic sympathetic nerve tract fibres from the spinal cord.
• Grey ramus communicans – Postganglionic nerve fibres for sympathetic tract

Question 2

What does the central nervous system comprise of?

Answer 2

Central = brain and spinal cord

Question 3

What does the peripheral nervous system innervate?

Answer 3

Peripheral nervous system = innervation to the limbs

Question 4

What does the somatic nervous system innervate?

Answer 4

Somatic = motor supply to somatic/ skeletal musculature AND VOLUNTARY

Question 5

What does the autonomic nervous system innervate?

Answer 5

Autonomic = supply the visceral smooth muscle and glands AND INVOLUNTARY

Question 6

Describe the structure of the spinal cord

Answer 6

1. The posterior primary ramus passes backwards between the transverse processes and then divides into a medial and lateral branch. These supply the adjacent vertebral muscles and send (from one or other branch) a cutaneous supply to the overlying skin.
2. The anterior primary ramus is linked to the sympathetic chain by a white and grey ramus communicans. It then runs in the body wall, and about half-way along its course gives off a lateral cutaneous branch which divides into anterior and posterior branches.

Question 7

What are the spinal nerves?

Answer 7

Spinal nerves
• mixed sensory and motor (segmental)
• formed from anterior and posterior roots
• exit via an intervertebral foramen

Question 8

What is Posterior primary ramus?

Answer 8

Posterior primary ramus
• smaller branch, passes posteriorly
• supplies paravertebral muscles
• also supplies overlying skin

Question 9

What is the Anterior primary ramus?

Answer 9

Anterior primary ramus
• much larger branch, passes anteriorly
• supplies limbs and most of body wall
• and skin of anterolateral body

Question 10

Describe the spinal cord blood supply

Answer 10

On image

Question 11

How is the spinal cord protected?

Answer 11

On image

Question 12

Describe the cervical plexus

Answer 12

• Arises from C1- C4/C5
• Contains the following: Cutaneous Branches – supply back of neck
• Ansa Cervicalis – supplies strap muscles of the neck
• Phrenic Nerve – C3, C4, C5 Remember Mnemonic – C3, C4, C5 – keeps the diaphragm alive!

Question 13

Describe the brachial plexus

Answer 13

Arises from C5-T1 – sensory and motor fibres
• Gives rise to the 5 Major peripheral nerves
• 5 Roots
• 3 Trunk
• 2 Divisions
• 3 Cords

Question 14

Describe the lumbosacral plexus

Answer 14

Arises from L1 – S3
• -lumbar plexus (L1 – L4)
• -lumbosacral trunk (L4 / L5) -sacral plexus (S1 – S3)

Question 15

What is the sciatic nerve?

Answer 15

• -largest nerve in the body

* -bifurcates to become the tibial and common fibular (or peroneal) nerves

Question 16

What are the major branches of the sciatic nerve?

Answer 16

femoral (quadriceps) -obturator (adductor muscles)
• -tibial (hamstrings, calf muscles)
• -common fibular/peroneal (anterior ‘leg’)