Notes - Control & Coordination - Class 10

Control & Coordination

Overview: Nervous System, Reflex Arc, Brain, Plant Hormones, Animal Hormones.

1. Nervous System

Neuron: Structural and functional unit. Dendrite (receive) → Cell body → Axon → Nerve ending (transmit).

Synapse: Gap between two neurons where signal passes as chemical.

Reflex Arc: Stimulus → Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector (Muscle) → Response.

2. Human Brain

Forebrain: Cerebrum (Thinking, Memory, Voluntary actions).
Midbrain: Involuntary actions (Pupil size).
Hindbrain: Cerebellum (Balance/Posture), Medulla (BP, Salivation, Vomiting), Pons.

3. Plant Coordination

Tropic Movements (Directional): Phototropism (Light), Geotropism (Gravity), Chemotropism (Chemicals/Pollen), Hydrotropism (Water).

Nastic Movements (Non-directional): Touch-me-not (Thigmonasty).

Hormones: Auxin (Growth), Gibberellin (Stem growth), Cytokinin (Cell division), Abscisic Acid (Inhibits growth/Wilting).

4. Animal Hormones

Thyroxin (Thyroid) - Metabolism. (Iodine needed).
Growth Hormone (Pituitary) - Height.
Adrenaline (Adrenal) - Emergencies (Fight/Flight).
Insulin (Pancreas) - Blood sugar. (Diabetes).
Testosterone/Estrogen - Puberty.

NCERT In-Text Questions (Solved)

Page 119

Q1. Difference between reflex action and walking?

Reflex action: Involuntary, rapid, automatic response to stimulus. Controlled by Spinal Cord. (Touching hot plate).
Walking: Voluntary action. Controlled by Forebrain (Cerebellum balances). We think and walk.

Q2. What happens at synapse?

Electrical signal reaches axonal end, releases chemicals (neurotransmitters). These cross the gap (synapse) and start a similar electrical impulse in dendrite of next neuron.

Q3. Part of brain maintaining posture and balance?

Cerebellum (part of Hindbrain).

Q4. How do we detect smell of agarbatti (incense stick)?

Olfactory receptors in nose detect smell. Send message to Olfactory lobe in Forebrain. Brain interprets it.

Q5. Role of brain in reflex action?

Reflex arcs are formed in spinal cord (for speed). But input also goes to brain. Brain records the event for future memory but doesn't control the immediate action.

Page 122

Q1. Plant hormones involved?

Auxins, Gibberellins, Cytokinins, Abscisic Acid. They coordinate growth, development and response.

Q2. How movement of sensitive plant leaves different from movement of shoots towards light?

Sensitive plant (Touch-me-not): Nastic movement (Non-directional), fast, due to turgor change.
Shoot to light: Tropic movement (Directional), slow, due to growth (Auxin).

Q3. How auxin promotes growth of tendril?

Auxin diffuses to the side of tendril away from support. It stimulates faster growth of cells on that side. This causes tendril to curve/bend around the support.

Q4. Experiment for hydrotropism?

Take germinating seeds in moist sawdust on a sieve. Roots grow down (Geotropism) then bend towards moist sawdust (Hydrotropism), overcoming gravity. This shows Hydrotropism > Geotropism.

Page 125

Q1. How chemical coordination occurs in animals?

Through Hormones secreted by endocrine glands directly into blood. They reach specific target organs to modify functions.

Q2. Use of iodised salt advised?

Iodine is essential for Thyroid gland to make Thyroxin hormone. Thyroxin regulates metabolism. Deficiency causes Goitre (swollen neck).

Q3. Body response to adrenaline?

Heart beats faster (more Oxygen to muscles). Blood diverted from skin/digestive system to muscles. Breathing rate increases. Prepares for "Fight or Flight".

Q4. Why diabetes patients treated with insulin?

Diabetics have high blood sugar level because their pancreas doesn't produce enough Insulin. Insulin injection helps regulate blood sugar level.

Exercise Solutions - Coordination - Class 10

NCERT Exercise Questions

Complete solutions for Chapter 6 exercises.

Q1. Which is a plant hormone?

(d) Cytokinin. (Insulin, Thyroxin, Oestrogen are animal hormones).

Q2. Gap between two neurons is called?

(b) Synapse.

Q3. Brain is responsible for?

(d) All of the above (Thinking, Balancing body, Regulating heartbeat).

Q4. Function of Receptors? If not working properly?

Receptors detect stimuli from environment (Heat, Sound, etc.). If receptors don't work, we can't detect changes/dangers, reflex actions won't work, leading to harm (e.g., burning hand).

Q5. Structure of Neuron and function.

Structure: Cell body (Cyton), Dendrites (branching fibres), Axon (long fibre), Nerve ending.
Function: Transmit information via electrical impulses.

Q6. Phototropism in plants?

Movement of plant parts in response to light.
- Shoots bend towards light (Positive phototropism).
- Roots bend away from light (Negative phototropism).

Q7. Spinal cord injury signals disrupted?

Reflex actions and involuntary actions will be disrupted. Signals from body to brain and brain to body pass through spinal cord, so paralysis/loss of sensation may occur.

Q8. Chemical coordination in plants vs animals?

Plants: Simple hormones (Auxin, etc.) regulate growth/movement. No specific glands/blood. Diffusion.
Animals: Complex endocrine system. Specific glands secrete hormones into blood. Target organs. Feedback mechanism.

Q9. Need for system of control and coordination?

Multicellular organs have complex body. Different organs work together. To synchronize their activities (e.g., running requires muscle + breathing + heart rate coordination) and respond to environment efficiently.

Q10. Involuntary actions and Reflex actions?

Involuntary: Automatic actions controlled by Midbrain/Hindbrain (Heartbeat, Breathing). Constant.
Reflex: Sudden response to stimulus controlled by Spinal Cord (Pulling hand from fire). Occasional.

Q11. Nervous vs Hormonal mechanism?

Nervous: Electrical impulses. Very fast. Short-lived. Specific cells.
Hormonal: Chemical messengers. Slow. Long-lasting. Widespread effect.

Q12. Mechanism of Sensitive plant movement?

Nastic movement (Thigmonasty). No growth involved. Cells change turgor pressure (water content). Water moves out of cells causing them to shrink and leaves droop.

Formulas & Facts - Control & Coordination - Class 10

Key Hormones & Facts

List of hormones, glands, and functions.

Important Hormones (Animal)

Growth Hormone Pituitary Gland

Thyroxin Thyroid Gland (Needs Iodine)

Adrenaline Adrenal Gland (Emergency)

Insulin Pancreas (Lowers Sugar)

Testosterone Testis (Male)

Oestrogen Ovary (Female)

50 Important Facts

1. Neuron is the longest cell in body.

2. Neurons do not divide.

3. Synapse acts as one-way valve.

4. Reflex actions are faster than thoughts.

5. Spinal cord controls reflex actions.

6. Brain is protected by Cranium.

7. Cerebrum is the thinking part.

8. Cerebellum controls posture mechanism.

9. Medulla controls heartbeat/breathing.

10. Hypothalamus controls body temperature.

11. Auxin is a growth promoter.

12. Auxin causes phototropism.

13. Gibberellins help in stem growth.

14. Cytokinins promote cell division.

15. Abscisic acid (ABA) inhibits growth.

16. ABA causes wilting of leaves.

17. Ethylene causes fruit ripening.

18. Phototropism means movement towards light.

19. Geotropism means movement towards gravity.

20. Roots are positively geotropic.

21. Shoots are negatively geotropic.

22. Chemotropism: Growth of pollen tube.

23. Thigmotropism: Growth of tendrils (Touch).

24. Nastic movements are non-directional.

25. Touch-me-not shows Seismonasty.

26. Endocrine glands are ductless glands.

27. Hormones are chemical messengers.

28. Adrenaline is Fight or Flight hormone.

29. Iodine prevents Goitre.

30. Insulin regulates blood glucose.

31. Diabetes is caused by Insulin deficiency.

32. Pancreas acts as both exocrine and endocrine gland.

33. Pituitary is the Master Gland.

34. Growth Hormone excess causes Gigantism.

35. Growth Hormone deficiency causes Dwarfism.

36. Testosterone causes puberty in males.

37. Estrogen causes puberty in females.

38. Feedback mechanism controls hormone amount.

39. Nervous acting is fast but short-lived.

40. Hormonal acting is slow but long-lasting.

41. Electric impulses can't reach every cell.

42. Chemical signals reach every cell.

43. Brain consumes 20% of body oxygen.

44. CSF protection against shock.

45. Walking in a straight line is maintained by Cerebellum.

46. Picking up a pencil is voluntary action.

47. Vomiting is controlled by Medulla.

48. Salivation is involuntary.

49. Plants don't have nervous system.

50. Plants don't have muscles to move.

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