1. Structure of Neuron: Cell body (contains nucleus),
Dendrites (receive impulses), Axon (transmit impulses), Nerve endings (synapse with next neuron/effector).
2. Synapse: Gap between two neurons. Nerve impulse causes
release of neurotransmitters (chemicals) that cross the gap and trigger impulse in next neuron.
3. Transmission of Nerve Impulse: Stimulus → Receptor →
Sensory neuron → Relay neuron → Motor neuron → Effector (muscle/gland) → Response.
4. Reflex Action: Quick, automatic, involuntary response to
a stimulus without conscious thought. Examples: Knee-jerk, withdrawing hand from hot object.
5. Reflex Arc: Receptor → Sensory neuron → Spinal cord
(Relay neuron) → Motor neuron → Effector. It bypasses the brain for faster response.
6. Why are reflexes important? They protect us from harm by
responding faster than conscious thought. The brain is informed later for learning.
7. Cerebrum (Fore-brain): Largest part. Controls thinking,
memory, intelligence, voluntary actions, and receives sensory information.
8. Cerebellum (Hind-brain): Controls balance, posture, and
coordination of voluntary movements.
9. Medulla Oblongata: Controls involuntary actions like
heartbeat, breathing, blood pressure, salivation, vomiting.
10. Hypothalamus: Controls hunger, thirst, body temperature,
and links nervous system to endocrine system.
11. Auxin: Promotes cell elongation, phototropism,
geotropism. Moves away from light in shoots, causing bending towards light.
12. Gibberellins: Promotes stem elongation, seed
germination, breaking dormancy.
13. Cytokinins: Promotes cell division, delays aging of
leaves.
14. Abscisic Acid (ABA): Inhibits growth, causes wilting of
leaves (stomatal closure during stress), promotes seed dormancy.
15. Ethylene: Promotes fruit ripening and senescence. Used
commercially to ripen fruits.
