According to the textbook:

• Schwann cells (A) envelop myelinated nerve fibres and form the Myelin Sheath (III) around the axon .
• Synaptic knob (B) is the bulb-like terminal of an axon branch which possesses synaptic vesicles containing chemicals called Neurotransmitters (I) .
• Bipolar neurons (C) (with one axon and one dendrite) are found in the Retina (IV) of the eye .
• Multipolar neurons (D) (with one axon and two or more dendrites) are found in the Cerebral cortex (II) .