Short Questions Answer
1. What are receptors?
Answer: Receptors are specialised tips of nerve cells that detect information from the environment.
2. What is a synapse?
Answer: A synapse is the gap between two neurons where transmission of impulses occurs through chemicals.
3. Which part of the brain controls posture and balance?
Answer: The cerebellum (part of the hind-brain).
4. Name the part of the brain responsible for thinking.
Answer: The fore-brain.
5. What is a reflex action?
Answer: A reflex action is an automatic and rapid response to a stimulus without conscious thought.
6. What protects the brain and spinal cord?
Answer: The brain is protected by the skull and cerebrospinal fluid; the spinal cord by the vertebral column.
7. What causes movement in plant leaves like the touch-me-not plant?
Answer: Movement occurs due to change in water content in plant cells, not growth.
8. What is phototropism?
Answer: It is the directional growth of a plant part in response to light.
9. Name any two plant hormones.
Answer: Auxin and Gibberellin.
10. What is the role of auxin in plants?
Answer: Auxin promotes cell elongation and helps in phototropic movement.
11. Which gland secretes adrenaline?
Answer: The adrenal gland.
12. Why is iodised salt necessary?
Answer: Because iodine is needed for the thyroid gland to produce thyroxin.
13. Which hormone regulates blood sugar level?
Answer: Insulin.
14. What are involuntary actions?
Answer: Actions not under our conscious control, e.g., heartbeat and breathing.
15. What is the function of cytokinins?
Answer: Cytokinins promote cell division, especially in fruits and seeds.
Long Questions Answer
1. Explain the structure and function of a neuron.
Answer: A neuron consists of dendrites, cell body, and axon. Dendrites receive impulses, the cell body processes them, and the axon transmits them to the next neuron or effector through synapses. Neurons form a network to conduct information across the body.
2. Describe the sequence of events in a reflex action.
Answer: When a receptor detects a stimulus (like heat), sensory neurons carry the message to the spinal cord. The spinal cord processes it and sends a response through motor neurons to the effector (muscle), causing an instant action such as pulling the hand away.
3. Explain the different parts and functions of the human brain.
Answer:
- Fore-brain: Main thinking part; controls voluntary actions and stores sensory information.
- Mid-brain: Controls some involuntary actions and reflexes.
- Hind-brain: Includes cerebellum and medulla; controls posture, balance, and vital activities like breathing and heartbeat.
4. What are plant hormones? Describe their main types and functions.
Answer: Plant hormones are chemical substances that regulate growth and responses.
- Auxins: Promote cell elongation and phototropism.
- Gibberellins: Help in stem growth.
- Cytokinins: Promote cell division.
- Abscisic acid: Inhibits growth and causes leaf wilting.
5. Differentiate between the movement in a sensitive plant and movement in animals.
Answer:
- Sensitive Plant: Movement is due to change in water content; no nerves or muscles involved.
- Animals: Movement is due to muscle contraction controlled by the nervous system.
6. What is adrenaline? Explain its role in the human body.
Answer: Adrenaline is a hormone secreted by the adrenal gland during stress or fear. It increases heart rate, breathing, and blood flow to muscles, preparing the body for “fight or flight”.
7. Describe how chemical coordination takes place in animals.
Answer: Hormones secreted by endocrine glands travel through the bloodstream to target organs. For example, insulin regulates blood sugar, thyroxin controls metabolism, and growth hormone regulates body growth.
8. Explain the feedback mechanism of hormone regulation using insulin as an example.
Answer: When blood sugar rises, the pancreas releases insulin, which lowers the sugar level. Once normal levels are restored, insulin secretion reduces — this balance is called the feedback mechanism.
Leave a Reply