Select the correct answers to the questions from the given options. (Do not copy the questions, write the correct answer only.)
Assertion (A): Arachnoid layer helps in speeding up the transmission of nerve impulses along the axons. Reason (R): Axon endings at the synapse secrete acetylene.
Topic: Assertion-Reason — arachnoid layer and neurotransmitter
Try it
Pick an option and check your answer. The full worked answer is below either way.
Answer
(d) Both (A) and (R) are false.
BOTH STATEMENTS ARE FALSE — and each contains a substituted word that a hurried reader will miss.
THE ASSERTION IS FALSE. The ARACHNOID is the middle one of the three MENINGES, the membranes that PROTECT the brain and spinal cord. It has no role in conducting impulses. The structure that speeds transmission along an axon is the MYELIN SHEATH, which insulates the fibre so that the impulse leaps from node to node.
THE REASON IS FALSE. The neurotransmitter secreted at the synapse is ACETYLCHOLINE. ACETYLENE is a hydrocarbon gas used in welding torches — an entirely different substance that merely sounds similar.
So both are false — option (D).
THE LESSON: assertion-reason questions are often built by swapping one technical term for a similar-sounding one. Arachnoid for myelin sheath, acetylene for acetylcholine. Read each noun deliberately rather than skimming for general plausibility.
Both (A) and (R) are false.