Nerves

Question 1

Define Motor unit

Answer 1

An efferent neurone and all the muscle fibres it innervates

Question 2

If a nerve is damaged through traumatic injury or disorder of NS, the muscle group innervated by the nerve will cease to function. Loss of the posterior forearm muscle group leads to what?

Answer 2

Wrist-drop

Question 3

In what 2 ways do somatic nerves emerge from the spinal cord?

Answer 3

Sensory dorsal (posterior) nerve root
Motor ventral (anterior) nerve root

Question 4

Sensory dorsal (posterior) nerve root and motor ventral (anterior) nerve root join to form what? Where do they join

Answer 4

They form a mixed spinal nerve, in the intervetebral foramen

Question 5

The mixed spinal nerve exits the intevertebral foramen laterally and branches into what?

Answer 5

A dorsal and a ventral ramus

Question 6

What does the ventral ramus supply?

Answer 6

Skin, muscles and bones of anterolateral sides of the trunk, and the entire upper body and lower limbs

Question 7

What does the dorsal ramus supply?

Answer 7

Posterior side of trunk only

Question 8

Do dorsal rami supply the limbs?

Answer 8

No

Question 9

What does the dorsal root carry?

Answer 9

Afferent fibres

Question 10

What does the ventral root carry?

Answer 10

Motor fibres

Question 11

What does the mixed spinal nerve carry?

Answer 11

Motor and sensory fibres

Question 12

What does the dorsal and ventral rami carry

Answer 12

Motor and sensory fibres

Question 13

Define cutaneous iinnervation

Answer 13

The area of skin which is supplied by a specific cutaneous nerve.

It contains fibres from several spinal nerves

Question 14

Define dermatome

Answer 14

An area of skin served by a single spinal nerve - arising from only one level of the spinal cord

Question 15

In which part of the body are cutaneous nerves and dermatomes the same?

Answer 15

Thorax and abdomen

Question 16

In which part of the body are cutaneous nerves and dermatomes different, and why?

Answer 16

In the limbs. This is due to plexus formation of spinal nerves.

During development, limbs are “pulled out” from the trunk

Question 17

Why is it important for clinicians to understand dermatomal distribution?

Answer 17

To identify the cutaneous nerve involved in a deficit, and pinpoint the exact single spinal nerve that is responsible for non-function

Question 18

Partial overlap of adjacent dermatome means if nerve supply to one dermatome is lost, what happens?

Answer 18

A reduction in sensitivity of the skin of that dermatome, but not complete loss.

Question 19

Generally, nerve damage nearer the spinal cord involves what?

What about peripheral injuries?

Answer 19

Individual nerve roots and dermatomes

Peripheral - more than one nerve root and dermatome

Question 20

What joint occurs in the midline of the trunk at dermatome T2

Answer 20

Sternocostal joint

Question 21

What surface features of the body are found at dermatome T4

Answer 21

Nipples

Question 22

What surface feature of the body marks the dermatome T10?

Answer 22

Navel

Question 23

In what region of the body is the dermatome L1 found?

Answer 23

Groin

Question 24

The dermatomes of the thoracic trunk at the sternomanubrial joint jum from C5, just above the joint, directly to T2, just below the joint.

Where have dermatomes C5-T1 been diverted?

Answer 24

Posterior - neck and shoulders

Question 25

Define myelin

Answer 25

A fatty white substance that surrounds the axon of some nerve cells, forming an electrically insulating layer

Question 26

What secretes myelin?

Answer 26

Schwann cells

Question 27

Define endoneurium

Answer 27

A layer of delicate connective tissue around the myelin sheath of each nerve fibre

Question 28

Each fascicle lies in a protective sheath called what?

Answer 28

Perineurium

Question 29

In sufficiently large nerves, multiple fascicles may be bundled in a sheath called what? What are their features

Answer 29

Epineurium

Each has a blood supply and fatty tissue

Question 30

What surrounds:
Individual axons
Nerve fascicles
A nerve?

Answer 30

Individual axons - endoneurium
Nerve fascicles - perineurium
A nerve - epineurium