Question

Consider the following statements and state true or false.
1. Synaptic cleft of neurons secrete adrenaline.
2. Myelinated nerve fibres and enveloped with Schwann cells, which form a myelin sheath around the axon.
3. Non-myelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath.
4. Spinal cord and cranial nerves are made up of non-myelinated nerve fibres.

• A. 1, 2 are correct but 3 and 4 are wrong.
• B. 1 and 4 are correct while 2 and 3 are wrong.
• C. 1, 2 and 3 are correct but 4 is wrong.
• D. 3 and 4 are correct while 2 and 3 are wrong.
• E. 2 and 3 are correct while 1 and 4 are wrong.

Answer 1

Answer: (E)

Myelin sheath is the insulating envelope of myelin, that surrounds the core of a nerve fiber or axon and that facilitates the transmission of nerve impulses, formed from the cell membrane of the Schwann cell in the peripheral nervous system and from oligodendroglia cells. Nonmyelinated nerve fiber lacks the fatty myelin insulating sheath. Such fibers form the gray matter of the nervous system, as distinguished from the white matter of myelinated fibers.