REVISION SUMMARY: Control and Coordination (NCERT Class 10)
1. Chapter at a glance
- Living organisms use control and coordination systems to respond to environmental changes; in multicellular animals this is achieved by specialised nervous and muscular tissues.
- Information is acquired by receptors at dendritic tips of neurons, converted into electrical impulses that travel from dendrite to cell body to axon, and transmitted across synapses by chemicals.
- Reflex arcs formed in the spinal cord enable quick responses without involving the thinking process of the brain.
- The brain (fore-brain, mid-brain, hind-brain) integrates sensory input, controls voluntary actions, and regulates involuntary actions such as blood pressure and salivation via the medulla and cerebellum.
- Brain and spinal cord (central nervous system) are protected by bony enclosures and fluid cushions; peripheral nerves connect them to the rest of the body.
- Plants lack nervous tissue and use electrical-chemical signals plus hormones for coordination; movements may be growth-independent (e.g., sensitive plant) or growth-dependent (tropisms).
- Directional growth responses (phototropism, geotropism, hydrotropism, chemotropism) are mediated by plant hormones such as auxin, gibberellins, cytokinins and abscisic acid.
- Animal hormones (e.g., adrenaline, thyroxin, insulin, growth hormone, testosterone, oestrogen) provide chemical coordination; their timing and quantity are regulated by feedback mechanisms.
2. Definitions and laws
The chapter contains no boxed/highlighted definitions, laws or formulas. Key terms are described in context only (neuron, synapse, reflex arc, central/peripheral nervous system, tropism, hormone, endocrine system, feedback mechanism). No SI units are applicable.
3. Important diagrams and activities
- Fig. 6.1(a) Structure of neuron – shows dendrite (information acquisition), axon (impulse conduction) and cell body.
- Fig. 6.1(b) Neuromuscular junction – illustrates chemical transmission from neuron to muscle/gland.
- Fig. 6.2 Reflex arc – demonstrates direct connection between sensory and motor neurons in spinal cord for rapid response.
- Fig. 6.3 Human brain – labels fore-brain (sensory/motor areas), mid-brain and hind-brain (medulla, cerebellum) with their functions.
- Fig. 6.4 Sensitive plant (Mimosa) – illustrates movement due to change in water content of cells, independent of growth.
- Fig. 6.5 Phototropism activity (bean seedlings in box) – shows shoots bending towards light and roots away.
- Fig. 6.6 Geotropism – depicts roots growing downward and shoots upward in response to gravity.
- Fig. 6.7 Endocrine glands (male/female) – locates pituitary, thyroid, adrenal, pancreas, testes/ovaries.
- Activity 6.1 Taste with/without blocked nose – demonstrates role of olfactory receptors in flavour perception.
- Activity 6.2 Phototropism experiment – proves directional growth response to light.
- Activity 6.3 Identification of endocrine glands – reinforces location and function of hormone-secreting glands.
- Activity 6.4 Hormone table completion – links glands, hormones and functions.
4. Common misconceptions and exam pitfalls
- Assuming all movements in plants involve growth (text distinguishes growth-independent touch response from growth-dependent tropisms).
- Confusing reflex actions with voluntary actions or thinking that the brain is always required for reflexes.
- Believing plants possess nervous tissue or that animal hormones directly cause directional growth like plant auxins.
- Overlooking that electrical impulses cannot reach every cell and cannot be generated continuously, hence chemical (hormonal) coordination is also needed.
- Mixing up specific brain parts (e.g., attributing posture/balance to fore-brain instead of cerebellum) or hormone functions (e.g., adrenaline vs. insulin).
- Forgetting feedback regulation when explaining why precise quantities of hormones are secreted.
5. Formula sheet
No formulas, equations or quantitative relationships are present in the chapter.