An axon are tiny connections in the nervous system from where electrical signals move to other neurons. Thats how your brains tell you someone is touching you, or you are feeling pains for example.

In Central Nervous System, CNS (including CN II), myelin is synthesized by oligodendrocytes.

In Peripheral Nervous System, PNS (including CN III-XII), myelin is synthesized by Schwann cells.

Mnemonic: 

COPS (CO PS) 

CNS = Oligodendrocytes, 

PNS = Schwann cells.

1. Abducens nerve or Cranial nerve VI (6)

2. Trochlear nerve or Cranial nerve IV (4)

3. Oculomotor nerve or Cranial nerve III (3)

• LR6 (SO4) R3

• LR6 = Lateral Rectus muscle --> Innervated by CN6 (VI) Abducens

• SO4 = Superior Oblique  muscle --> Innervated by CN4 (IV) Trochlear

• R3 = The Rest of the 4 eyeball movers --> Innervated by CN3 (III)  

1. Superior Rectus

2. Inferior Rectus

3. Medial Rectus

4. Inferior Oblique

The Oblique muscles take the eyeballs in the opposite direction. For example the Left Oblique is tested with the patient looking Right and .

Obliques go Opposite (Left SO and IO tested with patient looking right).

I O U: IO tested looking Up.