Chapter 6 — Control and Coordination

Chapter 6 of the Class 10 Science NCERT textbook, "Control and Coordination", covers the mechanisms by which the nervous system and hormones enable animals and plants to detect environmental stimuli and respond appropriately through electrical impulses, reflex arcs, brain regions, and chemical signals.

• The nervous system and reflexes — In animals, neurons carry information as electrical impulses and pass it across synapses to other cells. This allows fast reflex actions handled by the spinal cord and deliberate voluntary actions coordinated by the brain.
• How plants respond without nerves — Lacking nerves, plants coordinate through directional growth movements called tropisms, such as bending toward light. Hormones like auxin, gibberellins, cytokinins, and abscisic acid control this growth to promote or inhibit it.
• Chemical coordination by hormones — Animals also use chemical messengers — hormones such as adrenaline, insulin, and thyroxin — secreted by endocrine glands. Feedback mechanisms keep their levels balanced, so the body responds to needs without over- or under-reacting.

1. 01Neurons carry information as electrical impulses from dendrites through the cell body and axon; chemicals released at synapses bridge the gap to the next neuron or effector cell.
2. 02Reflex arcs are rapid, involuntary pathways processed in the spinal cord (not the brain), allowing quick responses such as withdrawing a hand from a flame.
3. 03The human brain has three regions: fore-brain (thinking, sensory areas), mid-brain/hind-brain (involuntary actions, blood pressure, salivation), and cerebellum (posture and balance).
4. 04Plants show two types of movement: growth-independent (e.g., sensitive plant folding leaves via water pressure changes) and growth-dependent tropisms (phototropism, geotropism, hydrotropism, chemotropism).
5. 05Auxin synthesised at the shoot tip causes unequal cell elongation, bending the plant towards light; gibberellins and cytokinins promote growth while abscisic acid inhibits it and causes leaf wilting.
6. 06Animal hormones including adrenaline (fight-or-flight), insulin (blood sugar regulation), thyroxin (metabolism), and growth hormone (development) are secreted by endocrine glands and regulated by feedback mechanisms.