Q. Which statements are wrong? I.Synaptic cleft of neurons secrete adrenaline. II.Myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon. III.Non-myelinated nerve fibre is enclosed by a Schwann cell that does not form myelin sheath. IV.Spinal cord and cranial nerves are made of non-myelinated nerve fibres. Of the four statements,
A) I, II are correct but III and IV are incorrect
B) I, II and III are correct but IV is incorrect
C) III and IV are correct but I and II are incorrect
D) II and III are correct but I and IV are incorrect
Explanation
There are two types of axons-myelinated and non-myelinated. The myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier. Myelinated nerve fibres are found in spinal and cranial nerves. Non-myelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath around the axon, and is commonly found in autonomous and the somatic neural systems.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.