Assertion-Reason:
Assertion (A): Myelinated nerve fibers transmit signals faster compared to non-myelinated nerve fibres.
Reason (R): Due to the presence of a myelin sheath, nerve impulses are transmitted via saltatory conduction, which is significantly faster than continuous conduction in unmyelinated fibres.
Both A and R are true, and R is the correct explanation of A.
— Concept: This question tests your understanding of nerve impulse conduction, specifically the role of the myelin sheath…Concept: This question tests your understanding of nerve impulse conduction, specifically the role of the myelin sheath in increasing transmission speed.
Why (A) is correct:
The Assertion (A) states that myelinated nerve fibers transmit signals faster than non-myelinated ones, which is true. The Reason (R) correctly explains this by stating that the myelin sheath allows for saltatory conduction, where the impulse 'jumps' from one Node of Ranvier to the next. This saltatory conduction is indeed significantly faster than the continuous conduction seen in unmyelinated fibers, where the impulse has to depolarize every point along the membrane. Therefore, R is the correct explanation for A.
Why other options are wrong:
B) Both statements are true, and the reason directly explains the assertion.
C) Both the assertion and the reason are true statements.
D) Both the assertion and the reason are true statements.
Common Mistake: Students sometimes confuse the role of myelin in insulation with its role in saltatory conduction, or forget that continuous conduction is slower.
NEET Tip / Mnemonic: Think of myelin as a 'speed booster' for nerve impulses, allowing them to 'leap' (saltatory) instead of 'crawl' (continuous).
Correct Answer: (A)
Both A and R are true, and R is the correct explanation of A.