Nerve

Question 1

Resting membrane potential of nerve

Answer 1

-70 mV

Question 2

Classification of nerve injury

Answer 2

Neuropraxia
Axonia with recoverable disturbance of membrane potential at molecular level
DIstortion of myelin sheath
No Wallerian degeneration
Local conduction block

Axonotmesis
Axonal disruption, basal lamina and endoneurium and perineurium intact

Neurotmesis
Nerve completely transected

Question 3

Factors determining prognosis following nerve injury

Answer 3

Violence of injury
Delay between injury and repair
Age
Gap between nerve ends
Level of injury: Distal injury has better prognosis that proximal
Condition of nerve ends
Association with arterial/ bony injury
Type of nerve: Nerve that innervate one muscle have better prognosis than those with mixed cutaneous and muscle innervation

Question 4

Classification of nerve

Answer 4

Type A
A-alpha: large, myelinated, fast conduction (skeletal muscle)

A-Beta: Medium, myelinated, moderate conduction (touch)

A- Delta: Medium, myelinated, moderate conduction (Intrafusal fibre)

A-Gamma: Small, myelinated, moderate conduction speed (touch, pressure, temp, pain)

Type B: Preganglionic autonomic nerve

Type C: Slow pain, postganglionic autonomic nerve, slow conduction