Control and Coordination – Case-based Questions with Answers
Class 10
CBSE Board Examinations
Designed strictly as per NCERT — ideal for Class 10 board preparation
Instructions: These case-based questions are grouped by topic and follow the NCERT Class 10 syllabus for Chapter 6 — Control and Coordination. Read each scenario carefully, answer the questions that follow, and refer to the model answers for guidance.
Nervous System & Neurons (Case 1–6)
Case 1
Riya accidentally touches a hot kettle and immediately withdraws her hand. She feels the pain but by the time she realizes it, her hand is already away from the kettle.
Q1. Explain the sequence of events (reflex arc) that allowed Riya to withdraw her hand so quickly.
A1. Receptor (pain receptors in skin) detects heat → sensory neuron carries impulse to spinal cord → interneuron (relay) in spinal cord processes and connects to motor neuron → motor neuron sends impulse to arm muscles → effector (flexor muscles) contracts to withdraw hand. The brain receives information later, so the action is fast and protective.
Q2. Why is this reflex action faster than a voluntary response?
A2. Reflex is processed in the spinal cord without routing through the brain, reducing transmission time; fewer synapses and localized processing make it faster than voluntary (cerebrum-mediated) responses.
Case 2
A patient has damage to the myelin sheath in some neurons and shows symptoms of muscle weakness and slowed reactions.
Q3. Explain how damage to the myelin sheath affects nerve impulse conduction.
A3. Myelin insulates axons and enables saltatory conduction (impulses jump between nodes of Ranvier). Damage (demyelination) disrupts insulation, slows or blocks impulse propagation, causing delayed reflexes, muscle weakness, numbness, and coordination problems.
Q4. Name a human disease involving demyelination and one major symptom.
A4. Multiple sclerosis; common symptoms include muscle weakness, impaired coordination, and visual disturbances.
Case 3
A biologist observes three cells under a microscope: Cell A has many dendrites and a single long axon; Cell B is elongated and forms a bundle; Cell C surrounds neurons and provides support.
Q5. Identify Cell A, B, and C.
A5. Cell A = neuron (nerve cell); Cell B = nerve (bundle of axons/fibres); Cell C = glial cell (supporting cell, e.g., Schwann cell or oligodendrocyte).
Q6. Briefly state the function of glial cells.
A6. Glial cells provide support, insulation (myelination), nutrient supply, and help maintain homeostasis in nervous tissue.
Synapse & Neurotransmission (Case 4–7)
Case 4
A researcher applies a drug that blocks calcium channels at the presynaptic terminal of a neuron and notices reduced neurotransmitter release.
Q7. Explain why blocking calcium channels reduces neurotransmitter release.
A7. Calcium influx into the presynaptic terminal triggers synaptic vesicles to fuse with the membrane and release neurotransmitters. Blocking calcium channels prevents this influx, reducing vesicle fusion and neurotransmitter release, impairing synaptic transmission.
Q8. Suggest how this drug might affect muscle activity if it acts at neuromuscular junctions.
A8. It would decrease acetylcholine release at neuromuscular junctions, weakening or blocking muscle contraction and potentially causing paralysis.
Case 5
During an experiment, two chemicals are observed: Chemical X causes depolarization of the postsynaptic membrane, while Chemical Y causes hyperpolarization.
Q9. Which of these is likely an excitatory neurotransmitter and which an inhibitory one? Give examples.
A9. Chemical X (causing depolarization) is excitatory (e.g., glutamate, acetylcholine at some synapses). Chemical Y (causing hyperpolarization) is inhibitory (e.g., GABA, glycine).
Q10. How does the balance between excitation and inhibition affect neuronal circuits?
A10. Balance prevents over-excitation (which can cause seizures) and ensures appropriate signal processing; inhibition shapes timing, prevents runaway activity, and enables complex behaviours.
Case 6
A patient is given a drug that inhibits acetylcholinesterase at synapses.
Q11. Predict the immediate effect of inhibiting acetylcholinesterase at cholinergic synapses.
A11. Inhibition prevents breakdown of acetylcholine, increasing its concentration in the synaptic cleft and prolonging stimulation of the postsynaptic receptor—leading to enhanced or prolonged muscle contractions or continuous activation of certain pathways.
Q12. Name one therapeutic use and one potential danger of acetylcholinesterase inhibitors.
A12. Therapeutic use: treatment of myasthenia gravis or Alzheimer’s disease (to boost cholinergic signaling). Danger: excessive activation can cause muscle cramps, respiratory failure, or cholinergic toxicity.
Reflexes & Clinical Correlates (Case 7–11)
Case 7
During a neurological exam, a doctor taps the patellar tendon and observes a normal knee-jerk reflex in one leg but a very weak response in the other.
Q13. What could a diminished knee-jerk reflex indicate?
A13. It may indicate damage to the peripheral nerve supplying that reflex arc, lower motor neuron lesion, or muscle disease; local sensory or motor pathway impairment should be investigated.
Q14. Why is the knee-jerk reflex considered monosynaptic?
A14. Because sensory neuron synapses directly with the motor neuron in the spinal cord without interneurons, making the response very fast.
Case 8
A child shows exaggerated tendon reflexes and spasticity in limbs after a head injury.
Q15. What type of motor neuron lesion is suggested and why?
A15. Upper motor neuron lesion (damage to motor pathways in brain or spinal cord) is suggested—characterized by hyperreflexia (exaggerated reflexes), spasticity, and increased muscle tone due to loss of inhibitory control from higher centres.
Q16. Explain how loss of brain inhibition leads to exaggerated reflexes.
A16. The brain normally sends inhibitory signals that modulate reflex arcs. When these descending inhibitory pathways are damaged, spinal reflex circuits become overactive, resulting in exaggerated responses.
Case 9
While playing, a student gets a cut and the wound site contracts and bleeds less quickly than expected.
Q17. Describe the immediate nervous system-mediated response that helps reduce bleeding.
A17. Local pain receptors trigger sympathetic reflexes causing vasoconstriction (narrowing of blood vessels) around the injury, reducing blood flow. Additionally, reflex withdrawal and contraction of surrounding muscles may limit further damage.
Q18. How might the endocrine system also contribute to the body’s response to injury?
A18. Stress hormones (adrenaline) released by the adrenal medulla increase heart rate and redirect blood flow; cortisol from adrenal cortex modulates inflammation and promotes energy mobilization for repair processes.
Endocrine System & Hormonal Regulation (Case 12–16)
Case 10
A person feels thirsty, urinates frequently, and has high blood sugar levels on testing.
Q19. Which endocrine disorder is suggested and what is the basic hormonal problem?
A19. Diabetes mellitus is suggested. Basic problem: insufficient insulin production (Type 1) or insulin resistance (Type 2), leading to high blood glucose, osmotic diuresis (frequent urination), and dehydration (thirst).
Q20. Name two long-term complications of uncontrolled diabetes.
A20. Damage to eyes (retinopathy), kidneys (nephropathy), peripheral nerves (neuropathy), and cardiovascular disease (atherosclerosis) are common long-term complications.
Case 11
A teenage girl shows delayed growth and low energy; tests reveal low levels of thyroid hormones.
Q21. What condition is likely and how does thyroid hormone deficiency cause these symptoms?
A21. Hypothyroidism is likely. Thyroid hormones regulate metabolic rate and growth; deficiency slows metabolism causing fatigue, poor growth, weight gain, cold intolerance, and in children can impair physical and mental development.
Q22. How does the feedback mechanism involving the pituitary help regulate thyroid hormones?
A22. Low thyroid hormone levels stimulate the hypothalamus to release TRH, which causes the pituitary to secrete TSH, stimulating the thyroid to produce more thyroxine. When thyroxine rises, negative feedback reduces TRH and TSH release.
Case 12
A farmer treats harvested fruits with ethylene gas to speed up ripening before market.
Q23. Explain how ethylene promotes fruit ripening.
A23. Ethylene is a gaseous plant hormone that triggers biochemical changes—softening of cell walls, conversion of starches to sugars, and pigment changes—leading to coordinated ripening. It acts via gene regulation and enzyme activation involved in ripening.
Q24. Why must farmers handle ethylene carefully when storing mixed fruits?
A24. Ethylene diffuses and can induce ripening in nearby fruits, causing unwanted ripening and spoilage; sensitive crops should be stored separately to prevent premature ripening.
Plant Movements & Hormones (Case 17–20)
Case 13
A potted plant placed near a window shows stems bending toward the light over several days.
Q25. Which plant hormone is responsible for this and describe the mechanism?
A25. Auxin causes phototropism. Light causes auxin to redistribute to the shaded side of the stem, promoting cell elongation there. Differential growth makes the stem bend toward the light to maximize photosynthesis.
Q26. How would growth differ if the plant were placed in uniform light?
A26. If light is uniform, auxin distribution is more even, and stems grow straight upward (negative geotropism for shoots) without directional bending.
Case 14
A gardener notices that bean seeds treated with gibberellin germinate faster than untreated seeds.
Q27. Explain the role of gibberellins in seed germination.
A27. Gibberellins break seed dormancy by stimulating synthesis of enzymes that mobilize stored food reserves (e.g., amylases that convert starch to sugar), supplying energy and substrates for growth, leading to faster germination.
Q28. Suggest one agricultural use of gibberellins.
A28. Gibberellins are used to promote uniform germination, increase stem elongation in certain crops, induce flowering in seedless fruits, or improve malting in cereals.
Case 15
During a drought, a shrub’s leaves fold and the plant reduces growth.
Q29. Which hormone mediates these responses and how does it help the plant survive drought?
A29. Abscisic acid (ABA) mediates drought responses. ABA causes stomatal closure to reduce transpiration, slows growth, and induces dormancy-related genes—conserving water and energy until conditions improve.
Q30. Why is stomatal closure a trade-off for the plant?
A30. While stomatal closure conserves water, it reduces CO2 uptake and photosynthesis, limiting energy production and growth; this trade-off prioritizes survival over immediate growth.