📌 Key Points
- Nervous system: CNS (brain + spinal cord) + PNS (nerves). Controls coordination via electrical/chemical signals
- Neuron structure: Dendrites receive → Cell body processes → Axon transmits → Terminals release neurotransmitters
- Reflex arc: Stimulus → Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector → Response. Brain informed after
- Reflex actions: Automatic, rapid, protective. Controlled by spinal cord - faster than conscious response
- Brain regions: Cerebrum (thinking, voluntary), Cerebellum (balance), Medulla (vital functions)
- Hypothalamus: Bridges nervous and hormonal systems, controls pituitary gland, regulates temperature/hunger/thirst
- Hormones: Chemical messengers from endocrine glands. Slower but longer-lasting effects than nerves
- Major glands: Pituitary (growth), Thyroid (metabolism), Pancreas (blood glucose), Adrenal (stress)
- Pituitary: Master gland, controls other endocrine glands via releasing hormones
- Plant hormones: Auxins (elongation, geotropism), Gibberellins (growth), Cytokinins (cell division), Ethylene (ripening)
- Phototropism: Plant bends toward light - auxin concentrates on dark side causing uneven growth
- Geotropism: Plant roots bend toward gravity - positive geotropism in roots, negative in shoots
- Feedback mechanism: Body senses change, produces response, response brings level back to normal
- Somatic nervous system: Voluntary movements and sensory input. Under conscious control
- Autonomic nervous system: Involuntary functions - heart, digestion, breathing. Not conscious
- Synapse: Gap between neurons. Neurotransmitter chemicals cross gap enabling one-way transmission
- Endocrine vs exocrine: Endocrine secretes into bloodstream (hormones), exocrine secretes through ducts (sweat, saliva)
- Spinal cord: Transmits signals between brain and body. Also directly controls reflex actions
- Cerebral cortex: Outer layer of cerebrum - seat of consciousness, controls voluntary actions
- Insulin and glucagon: Pancreas hormones that regulate blood glucose in opposite ways
📘 Important Definitions
⚠️ Common Mistakes
✗ Wrong: Brain controls all reflex actions.
✓ Correct: Spinal cord directly controls reflex actions - brain is informed only after reflex completes. This makes reflex faster.
✗ Wrong: Reflex actions are voluntary and conscious.
✓ Correct: Reflex actions are automatic and involuntary. Occur without conscious thought through spinal cord control.
✗ Wrong: Hormones act immediately like nerves.
✓ Correct: Hormones act slowly (seconds to minutes) but have longer-lasting effects than rapid nerve signals.
✗ Wrong: Medulla controls thinking and voluntary movements.
✓ Correct: Medulla controls involuntary vital functions (breathing, heart). Cerebrum controls thinking and voluntary movement.
✗ Wrong: Auxins promote both root and shoot growth equally.
✓ Correct: Auxins promote root growth only at low concentration. At high concentration they inhibit growth (inhibit at root tips, promote at shoot).
✗ Wrong: Plant hormones work instantly like animal nervous system.
✓ Correct: Plant hormones work slowly through gene expression. Plants have no nervous system for rapid response.
📝 Exam Focus
These questions are frequently asked in CBSE exams:
🎯 Last-Minute Recall
Close your eyes and try to recall: Key definitions, formulas, and 3 common mistakes. If you can recall 80% without looking, you're exam-ready!