Chapter 6 Summary — Control and Coordination
Comprehensive quick-revision guide for last-minute preparation.
1. What is Control and Coordination?
Control and coordination = sensing changes (stimuli) and producing appropriate responses. Essential for survival, growth, reproduction.
2. Two Coordination Systems
| Nervous System | Endocrine System | |
|---|---|---|
| Signal | Electrical | Chemical (hormones) |
| Path | Neurons | Blood |
| Speed | Fast (ms) | Slow (min-days) |
| Duration | Brief | Long-lasting |
Plants only use endocrine (hormones) — no nervous system.
3. Nervous System
Components: 1. CNS = Brain + Spinal cord. 2. PNS = All other nerves (12 cranial pairs + 31 spinal pairs).
Brain — 3 Main Parts: 1. Forebrain (cerebrum) — thinking, voluntary movement, senses. 2. Midbrain — visual/auditory reflexes. *3. Hindbrain:
- Cerebellum — balance, coordination.
- Pons — bridge.
- Medulla — heart, breathing.*
Brain Protection: 1. Skull (cranium). 2. Meninges (3 membranes). 3. CSF (cushion fluid).
4. Neuron — Functional Unit
4 Parts: 1. Cell body (cyton) — has nucleus. 2. Dendrites — receive signals. 3. Axon — carries signals (myelin sheath speeds it). 4. Axon terminals — transmit via synapse.
3 Types: 1. Sensory — receptor → CNS. 2. Motor — CNS → effector. 3. Relay — within CNS.
5. Reflex Action
Immediate, involuntary, automatic response. Speed: ~0.1 sec. Bypasses brain (uses spinal cord).
Reflex Arc — 5 Components: Receptor → Sensory neuron → Spinal cord (relay) → Motor neuron → Effector.
6. Plant Coordination
Two Types of Movements: 1. Tropic — directional, growth-based (slow). 2. Nastic — non-directional, cell-pressure (fast, e.g., Mimosa).
5 Tropisms:
| Tropism | Stimulus | Direction |
|---|---|---|
| Phototropism | Light | Stems to light, roots away |
| Geotropism | Gravity | Roots down, stems up |
| Hydrotropism | Water | Roots toward water |
| Chemotropism | Chemicals | Pollen tube → ovary |
| Thigmotropism | Touch | Tendrils on supports |
All driven by auxin hormone.
7. 5 Plant Hormones
| Hormone | Function | Use |
|---|---|---|
| Auxin | Cell elongation, phototropism | Rooting from cuttings |
| Gibberellin | Stem elongation, germination | Bigger grapes |
| Cytokinin | Cell division | Tissue culture |
| ABA | Stress, stomata closure | Drought response |
| Ethylene | Fruit ripening (gas) | Banana ripening |
8. Major Endocrine Glands
| Gland | Hormone | Function |
|---|---|---|
| Pituitary (master) | GH, TSH, ADH, FSH, LH | Growth, controls others |
| Thyroid | Thyroxine | Metabolism (needs iodine) |
| Pancreas | Insulin, Glucagon | Blood sugar |
| Adrenal | Adrenaline | Fight or flight |
| Testes | Testosterone | Male traits |
| Ovaries | Oestrogen, Progesterone | Female traits, pregnancy |
9. Negative Feedback
Self-regulation: when output is high, body reduces production. Example: blood sugar regulation. Maintains homeostasis (internal balance).
10. Hormonal Disorders
| Disorder | Cause |
|---|---|
| Diabetes mellitus | Insulin problem |
| Goitre | Iodine deficiency |
| Cretinism | Iodine deficiency in children |
| Dwarfism | Low GH (childhood) |
| Gigantism | Excess GH (childhood) |
| Hyperthyroidism | Excess thyroxine |
| Hypothyroidism | Low thyroxine |
Quick Revision — Key Concepts
1. Coordination = sensing + responding to stimuli. 2. Two systems: nervous (fast) + endocrine (slow, lasting). 3. Plants use only hormones (no nervous system). 4. Reflex ≠ voluntary action (reflex faster, via spinal cord). 5. Cerebrum = thinking + voluntary; cerebellum = balance. 6. Pituitary = master gland. 7. Iodised salt prevents goitre + cretinism. 8. Insulin lowers blood sugar (without it = diabetes). 9. Adrenaline = fight or flight hormone. 10. Auxin drives plant tropisms (especially phototropism).
Key Numbers
- Brain neurons: ~86 billion.
- Brain weight: ~1.4 kg.
- Cranial nerves: 12 pairs.
- Spinal nerves: 31 pairs.
- Reflex speed: ~0.1 seconds.
- Conscious action: ~0.5-1 second.
- Synapses in brain: ~100 trillion.
- Normal blood sugar: 70-110 mg/dL.
- Normal BP: 120/80 mmHg.
Important Comparisons
Nervous vs Hormonal: Nervous = electrical, fast, brief (reflexes). Hormonal = chemical, slow, lasting (growth).
Tropic vs Nastic: Tropic = directional, growth (phototropism). Nastic = non-directional, pressure (Mimosa).
Cerebrum vs Cerebellum: Cerebrum = thinking, voluntary movement. Cerebellum = balance, coordination.
Type 1 vs Type 2 Diabetes: Type 1: insulin not produced. Type 2: insulin not effective (resistance).
Common Mistakes to Avoid
1. Don't say plants have nervous system — they only have hormones. 2. Don't confuse reflex with voluntary — reflex is via spinal cord. 3. Don't forget pulmonary artery exception — relevant in transport, not here. 4. Don't say Mimosa folding is tropic — it's nastic. 5. Don't confuse hormones with neurotransmitters — hormones use blood, neurotransmitters use synapses. 6. Diabetes types are different — type 1 needs insulin, type 2 may not.
Final Tips
1. Master diagrams — neuron, brain, reflex arc. 2. Memorise hormones — gland, function, disorder. 3. Practice comparisons — important for 3-5 mark questions. 4. Real-life applications — iodised salt, diabetes, adrenaline. 5. 5 plant hormones + 5 tropisms = guaranteed marks.
This chapter rewards memory + understanding. Master both for top marks!
All the best for your exam!