Q30
3 marksShort AnswerSection C

(a) List two constituents of Central Nervous System (CNS). How are these components protected from injuries? (b) Write two limitations of the use of electrical impulses.

Control and Coordination
Human Nervous System
Official Answer

(a) Two constituents of the Central Nervous System (CNS) and their protection:

  1. Brain: It is protected by a bony box called the skull (cranium). Inside this box, the brain is contained in a fluid-filled balloon (cerebrospinal fluid) which acts as a shock absorber.
  2. Spinal Cord: It is protected by a hard, bumpy structure called the vertebral column or backbone.

(b) Two limitations of the use of electrical impulses:

  1. Limited Reach: Electrical impulses reach only those cells that are directly connected by nervous tissue, and not each and every cell in the animal body.
  2. Reset Time (Refractory Period): Once an electrical impulse is generated in a cell and transmitted, the cell takes some time to reset its chemical mechanisms before it can generate and transmit a new impulse. Thus, cells cannot continually create and transmit electrical impulses.
BrainSpinal cordbony boxfluid-filled balloonshock absorptionvertebral columnbackboneconnected by nervous tissuereset its mechanismscontinually

Marking Scheme

  • 11 mark for listing Brain and Spinal Cord as the two constituents of CNS.
  • 21 mark for explaining the protection of both (bony box/fluid-filled balloon for brain, vertebral column for spinal cord).
  • 31 mark for listing two distinct limitations of electrical impulses (0.5 marks for each limitation).

Hint

For protection, think of the hard bony structures in your head and down your back, plus the fluid cushion. For limitations, think about which cells nerves can't reach and why a cell needs to rest after firing.

Quick Oral Answer

The two main parts of the CNS are the brain and the spinal cord. The brain is protected by the skull and a shock-absorbing fluid, while the spinal cord is protected by the backbone. Two limitations of electrical impulses are that they cannot reach every single cell, and cells need time to reset before sending another impulse.

Analysis & Explanation

Part (a) focuses on the structural protection of the central nervous system. The brain is highly delicate and is protected by both a hard outer shell (the skull) and a fluid cushion (cerebrospinal fluid) to absorb mechanical shocks. The spinal cord, which is a bundle of nerves extending downwards, is protected by the vertebral column.


Part (b) highlights the evolutionary necessity of chemical coordination (hormones). Since nervous tissue cannot connect to every single cell, and neurons require a recovery period to reset their ionic balance after firing an impulse, multicellular organisms rely on chemical messengers (hormones) for continuous and widespread communication.

Common Mistakes

  1. 1Forgetting to mention the fluid-filled balloon (shock absorber) when explaining the protection of the brain.
  2. 2Confusing the vertebral column with the spinal cord itself.
  3. 3Vaguely stating that electrical impulses are 'too fast' as a limitation, instead of explaining the reset time or lack of connection to all cells.

Interesting Facts

The fluid-filled balloon protecting your brain contains Cerebrospinal Fluid (CSF), which not only absorbs shocks but also makes the brain buoyant, reducing its effective weight from about 1400 grams to just 50 grams so it doesn't crush itself!

The human spinal cord is about 45 cm long in men and 43 cm long in women, yet it is protected along its entire length by 33 individual vertebrae.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2024?

This question carries 3 marks in the CBSE Class 10 Science 2024 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Control and Coordination" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Human Nervous System" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2024 paper?

This is a Short Answer question from Section C in the CBSE Class 10 Science 2024 paper.