C13 15-16

Question 1

Plexus

Answer 1

A network of converging and diverging nerve fibers. (ventral rami except thoracic)

Question 2

Four major plexes that innervate specific body regions?

Answer 2

Cervical (phrenic(serves diagphram)),
Branchial (radial),
Lumbar (femoral),
Sacral (sciatic)

Question 3

What is the advantage of a plexus?

Answer 3

An advantage of this fiber re-grouping is that damage to one spinal segment or root cannot completely paralyze any limb muscle. (alternative routes) Several nerves going to same part of body

Question 4

Cervical plexus

Answer 4

Phrenic nerve serves diaphragm sensory and motor. (hiccups!) (shigles)

Also Serves skin of neck/ear/back of the head/shoulder - sensory.

Question 5

Brachial plexus

Answer 5

Virtually all nerves that innervate the upper limb.

Radial - compression = Saturday night paralysis

Question 6

Lumbar plexus

Answer 6

Innervates femur/quadriceps.

Femoral (also ab wall/psoas muscles)

Question 7

Sacral plexus

Answer 7

Serves buttock and lower limb.

Sciatic

Question 8

Dermatome

Answer 8

Map of nerve distribution

Question 9

How are the spinal nerves formed?

Answer 9

Rootlets (coming off the spinal cord) —> form dorsal and ventral roots —> combine to form spinal nerves

Question 10

General features of spinal nerves?

Answer 10

proximal branches (dorsal root/dorsal root ganglion/ventral root),  
distal branches (dorsal ramus/ventral ramus/meningeal branch)

Question 11

Dorsal rami

Answer 11

Supply the posterior body trunk

Question 12

Ventral rami

Answer 12

Supply the trunk and the limbs (everything but the posterior body trunk)

Question 13

What are roots?

Answer 13

lie medial to and form the spinal nerves. Strictly sensory OR motor.

Question 14

What are ventral/dorsal rami?

Answer 14

lie distal to and are lateral branches of the spinal nerves. Carry both sensory and motor fibers.

Question 15

Which nerves do not form plexuses?

Answer 15

Intercostal nerves