Board PYQs — Control and Coordination
A curated collection of CBSE Board Previous Year Questions from 2018 to 2024.
Coverage: 1-mark MCQs, 2-mark short, 3-mark medium, 5-mark long.
This chapter typically contributes 8-10 marks to the Class 10 Science board paper.
Topic-wise Question Distribution (Last 5 Years)
| Topic | Frequency | Typical Marks |
|---|---|---|
| Neuron + Reflex Action | Very High | 3-5 |
| Human Brain | High | 3-5 |
| Plant Tropisms + Hormones | High | 2-3 |
| Endocrine Glands | Very High | 3-5 |
| Hormonal Disorders | High | 2-3 |
| Nervous vs Hormonal | Medium | 2-3 |
Strategy
1. Master Diagrams:
- Neuron structure.
- Reflex arc.
- Brain parts.
- Phototropism mechanism.
2. Compare-Contrast Questions:
- Nervous vs Hormonal.
- Tropic vs Nastic.
- Type 1 vs Type 2 diabetes.
- Cerebrum vs Cerebellum.
3. Memorise Hormones and Functions:
- Pituitary, thyroid, pancreas, adrenal, gonads.
- Plant hormones: auxin, gibberellin, cytokinin, ABA, ethylene.
4. Real-life Applications:
- Iodised salt → goitre prevention.
- Insulin → diabetes treatment.
- Adrenaline → fight or flight.
Master these for guaranteed 8-10 marks!
PYQ 1: CBSE Board 2024 — 1 mark
Q. Which gland is called the 'master gland'? (a) Thyroid (b) Pituitary (c) Adrenal (d) Pancreas
Answer: (b) Pituitary
Explanation: Pituitary is called 'master gland' as it controls many other endocrine glands. Located at base of brain.
PYQ 2: CBSE Board 2023 — 1 mark
Q. Define reflex action.
Answer: Reflex action = an immediate, involuntary, automatic response to a stimulus, controlled by spinal cord (bypassing brain). Speed: ~0.1 seconds.
PYQ 3: CBSE Board 2024 — 2 marks
Q. Define hormones. List 2 properties.
Answer:
'Hormones' = chemical messengers produced by endocrine glands that travel via blood to specific target cells.
2 Properties: 1. Effective in tiny amounts. 2. Act on specific target cells (with receptors). 3. Slow but long-lasting effects. 4. Travel through blood.
PYQ 4: CBSE Board 2022 — 3 marks
Q. What is phototropism? Explain with mechanism.
Answer:
'Phototropism' = directional growth of plants in response to light. Stems: positively phototropic (grow toward light). Roots: negatively phototropic.
Mechanism: 1. Tip of stem senses light. 2. Auxin moves to shaded side. 3. Cells with more auxin elongate more. 4. Stem bends toward light.
Discovered by Charles Darwin in 1880.
PYQ 5: CBSE Board 2024 — 3 marks
Q. Differentiate between nervous and hormonal coordination.
Answer:
| Feature | Nervous | Hormonal |
|---|---|---|
| Signal | Electrical (neurons) | Chemical (hormones) |
| Path | Through neurons | Via blood |
| Speed | Very fast (ms) | Slow (min-days) |
| Duration | Brief | Long-lasting |
| Examples | Reflexes | Growth, metabolism |
Both work together for complete coordination.
PYQ 6: CBSE Board 2023 — 5 marks
Q. Describe the structure of a neuron and explain reflex action with example.
Answer:
Neuron Structure (4 parts): 1. Cell body (cyton) — has nucleus. 2. Dendrites — receive signals. 3. Axon — carries signals away (covered with myelin sheath). 4. Axon terminals — transmit signals via synapse.
Reflex Action: Immediate, involuntary response (~0.1 seconds).
Example: Withdrawing hand from hot pan: 1. Skin (receptor) detects heat. 2. Sensory neuron → spinal cord. 3. Relay neuron processes. 4. Motor neuron → arm muscle. 5. Hand pulls back.
Bypasses brain — handled by spinal cord. Brain informed AFTER.
PYQ 7: CBSE Board 2022 — 3 marks
Q. Name 5 endocrine glands and one hormone each.
Answer:
| Gland | Hormone |
|---|---|
| Pituitary | Growth hormone |
| Thyroid | Thyroxine |
| Pancreas | Insulin |
| Adrenal | Adrenaline |
| Testes | Testosterone |
PYQ 8: CBSE Board 2024 — 5 marks
Q. Describe the human brain. State the major parts and their functions.
Answer:
3 Main Parts:
1. Forebrain: Largest part. Includes cerebrum, thalamus, hypothalamus. Functions: thinking, voluntary movements, senses, memory, emotions.
2. Midbrain: Functions: visual & auditory reflexes; connects forebrain to hindbrain.
3. Hindbrain: a) Cerebellum — balance, coordination. b) Pons — bridge, breathing. c) Medulla — heart rate, breathing, BP, vital reflexes.
Brain Protection: 1. Skull (bone). 2. Meninges (3 membranes). 3. CSF (cushion fluid).
PYQ 9: CBSE Board 2023 — 3 marks
Q. What is goitre? How can it be prevented?
Answer:
'Goitre' = enlarged thyroid gland. Caused by iodine deficiency.
Mechanism: Without iodine → thyroid can't make thyroxine → pituitary releases more TSH → thyroid enlarges.
Prevention: 1. Iodised salt (mandatory in India). 2. Iodine-rich foods: seafood, eggs, dairy. 3. Iodine supplements (in deficient regions).
PYQ 10: CBSE Board 2022 — 3 marks
Q. Compare insulin and glucagon.
Answer:
| Feature | Insulin | Glucagon |
|---|---|---|
| Source | Beta cells of pancreas | Alpha cells of pancreas |
| Effect | Lowers blood sugar | Raises blood sugar |
| When released | After meals (high sugar) | Between meals (low sugar) |
| Action | Cells take up glucose; storage as glycogen | Glycogen → glucose; released to blood |
Both maintain blood sugar via negative feedback.
Without insulin → diabetes (high sugar). Without glucagon → hypoglycemia (low sugar).
PYQ 11: CBSE Board 2024 — 2 marks
Q. Why is iodised salt mandated in India?
Answer:
Iodised salt is mandated to: 1. Prevent goitre (enlarged thyroid from iodine deficiency). 2. Prevent cretinism in children (mental retardation due to iodine deficiency in pregnancy/childhood).
Salt is universal (everyone consumes daily) → effective public health intervention. Successful in reducing iodine deficiency disorders in India.
PYQ 12: CBSE Board 2023 — 5 marks
Q. Describe the role of plant hormones with examples.
Answer:
| Hormone | Function |
|---|---|
| Auxin | Cell elongation; phototropism |
| Gibberellin | Stem elongation; seed germination |
| Cytokinin | Cell division; fruit growth |
| Abscisic Acid | Inhibitor; stomata closure (drought) |
| Ethylene | Fruit ripening (gas) |
Examples: 1. Auxin in cuttings: synthetic auxin promotes root formation. 2. Ethylene in fruit ripening: bananas, mangoes ripened with ethylene gas. 3. Gibberellin in grapes: sprayed for larger fruit. 4. ABA in drought: closes stomata to save water.
Plant hormones = chemical coordination in plants (no nervous system).
PYQ 13: CBSE Board 2022 — 3 marks
Q. What are tropic movements? Give 3 examples.
Answer:
'Tropic movements' = directional growth of plants in response to environmental stimuli.
Direction depends on stimulus.
3 Examples: 1. Phototropism — growth toward light (stems) or away from light (roots). 2. Geotropism — roots grow downward (gravity), stems upward. 3. Hydrotropism — roots grow toward water.
All driven by hormone auxin.
PYQ 14: CBSE Board 2021 — 5 marks
Q. What is feedback mechanism? Explain with example of blood sugar regulation.
Answer:
'Feedback mechanism' = self-regulating process where output controls its own input. Maintains homeostasis.
Negative feedback = reduces output to maintain balance. Most common in body.
Blood Sugar Regulation: 1. High sugar after meal: pancreas releases insulin → cells take glucose → sugar drops → pancreas stops insulin. 2. Low sugar between meals: pancreas releases glucagon → liver releases glucose → sugar rises → pancreas stops glucagon.
Insulin and glucagon are opposite hormones — together maintain stable blood sugar (70-110 mg/dL).
Loop ensures balance.
PYQ 15: CBSE Board 2024 — 5 marks
Q. (a) What is adrenaline? (b) Describe its 5 effects on the body. (c) Why is it called 'fight or flight' hormone?
Answer:
(a) Adrenaline: Hormone produced by adrenal medulla (above kidneys). Released during stress/danger/exercise.
(b) 5 Effects: 1. Heart rate increases. 2. Pupils dilate. 3. Breathing speeds up. 4. Liver releases glucose for energy. 5. Blood diverts to muscles (away from gut).
Result: body ready for action.
(c) 'Fight or Flight': Helps body either:
- Fight — defend against danger.
- Flight — run away from danger.
Evolutionary survival mechanism. Modern uses: sports, public speaking, emergencies.