PNS

Question 1

What percentage of neurones are in the PNS?

Answer 1

10%

Question 2

How many pairs of nerves are in the PNS?

Answer 2

43 pairs

12 cranial nerves and 31 spinal

Question 3

Where do the nerves leave compared to the vertebral bone?

Answer 3

Cervical = nerve leaves above but then for thoracic and after that, the nerve leaves below the verterbral bone

Question 4

Compare the somatic and autonomic nervous systems

Answer 4

SNS = voluntary effector e.g. muscle 
Single motor from spinal cord to target organ 
Always stimulators
Ach releases 
Not at rest 

ANS = involuntary effectors 
Involve pre and post ganglionic 
Stimulatory and inhibitory 
Ach or noradrenaline released 
Fires at rest

Question 5

What is a dermatome and myotome?

Answer 5

Dermatome = part of skin that is stimulated by spinal nerve 
Myotome = part of muscle that is stimulator by spinal nerve

Question 6

What do the dorsal and ventral rami innervate?

Answer 6

Dorsal = neck 
Ventral = everything else

Question 7

Describe the structure of the PNS nerve

Answer 7

Each axon surrounded by endoneurium
Many axons for a fascicle surrounded by perineurium
Many fascicles bundle together with blood vessels to form nerve fibre surrounded by epineurium

Question 8

What are the 3 groups of PNS neurones?

Answer 8

A = large diameter, high conduction, myelinated 
B = small diameter, low conductance, myelinated 
C = small diameter, low conductance, non-myelinated

Question 9

What are plexuses?

Answer 9

Intersecting spinal nerves

Question 10

What is neuropraxia?

Answer 10

Reversible conduction block e.g. due to nerve compression

Causes demyelination

Question 11

What is axonotmesis?

Answer 11

Degeneration below and proximal to lesion
Demyelination and axon loss
Endometrium effected

Question 12

What is neurotmesis?

Answer 12

Severe nerve injury
Damage to epinerium so no cell growth
Demyelination and axon loss

Question 13

What methods can be used to determine neuropathies?

Answer 13

EMG
Nerve conduction study= velocity of impulse
Somatosensory evoked potential

Question 14

What can effect the nerve conduction velocity?

Answer 14

Age of the patient as children below 4 will have very very slower conduction velocities

Question 15

How do you carry out a somatosensory evoked potential?

Answer 15

Stimulating electrodes on arms/legs
Recording on head/spine
Can determine time and quality of transmission