Question

Choose the correct statement(s) for axon of a neuron:

• A. Myelin sheath in humans is an alternative to a thick axon in giant squid.
• B. In CNS, myelin is produced by schwann cells.
• C. Nodes of Ranvier are booster sites for transmission of electrical signals.
• D. Smaller axons are often not myelinated.

Answer 1

Answer: (A), (C), (D)

Smaller axons are often not myelinated.

Myelin is a fatty white substance that acts like insulators and prevent the loss of electrical signals. In giant squid, instead of myelin, thick axons are present. Since it is not possible to have thick axons in humans due to enormous number of axons in our body, axons have a meylin sheath. In PNS and CNS, myelin is produced by schwann cell and oligodendrocytes respectively. Nodes of Ranvier are places where myelin sheath is absent in the axons. It speeds up electrical signals. Since smaller axons have smaller distance for travelling of nerve impulses hence, even without myelin sheath, the nerve impulse can be transmitted through the axon.