Science — CBSE Class 10 board question

(a) The two constituents of the Central Nervous System (CNS) are:

1. Brain
2. Spinal cord

Protection: The brain is protected by a hard bony box called the cranium, and the spinal cord is protected by the vertebral column. Both are further enclosed in three membranous layers called meninges.

(b) Two limitations of electrical impulses:

1. Electrical impulses can reach only those cells that are connected by nervous tissue — not all cells in the body are connected this way.
2. Once an impulse is delivered and the response is complete, the cell takes time to reset; thus, it cannot continuously transmit impulses.

• Part (a) is standard 2-mark content from the Control and Coordination chapter — always name both CNS components and mention both cranium and vertebral column for full marks. Mentioning meninges adds accuracy.
• Part (b) tests why chemical coordination (hormones) is also needed. Examiners expect limitations related to reach and continuity/speed for long-term responses. These are the textbook-stated reasons for needing a chemical communication system alongside the nervous system.