Rahul accidentally touched a hot pan while cooking. Instantly, he withdrew his hand without consciously thinking about it. Later, he recalled that he had not given his hand a command to move, yet it happened automatically. His teacher explained that such actions are controlled by the nervous system and are called reflex actions.
(a) What is a reflex action? (1 Mark)
(b) Explain the pathway of a reflex arc. (2 Marks)
(c) How is a reflex action different from voluntary actions? (1 Mark)
OR
(c) Which part of the brain controls involuntary actions like heartbeat and digestion? (1 Mark)
Ans:
(a) A reflex action is an automatic, quick response to a stimulus that does not involve conscious thought.
(b) The pathway of a reflex arc:
(c) Reflex actions are automatic and do not involve thinking, while voluntary actions are controlled by the brain and require conscious effort.
OR
(c) The medulla oblongata in the hindbrain controls involuntary actions like heartbeat and digestion.
During a sports event, Ananya had to catch a fast-moving ball. She was able to judge its speed, position, and direction and coordinate her hand movements to catch it. Her teacher explained that the human brain is responsible for these complex actions and different parts of the brain control different activities.
(a) Which part of the brain controls voluntary actions? (1 Mark)
(b) Explain the functions of the cerebellum in maintaining body balance. (2 Marks)
(c) What is the role of the spinal cord in nervous coordination? (1 Mark)
OR
(c) How is the brain protected inside the human body? (1 Mark)
Ans:
(a) The cerebrum in the forebrain controls voluntary actions.
(b) The cerebellum is responsible for:
(c) The spinal cord serves as a communication pathway between the brain and the rest of the body, conducting nerve impulses.
OR
(c) The brain is protected by:
Ravi noticed that when he touched the Mimosa pudica (Touch-Me-Not) plant, its leaves folded quickly. However, he observed that when a sunflower plant responded to sunlight, the movement was slow. His teacher explained that plant movements can be of two types—growth-dependent and growth-independent.
(a) How does the Touch-Me-Not plant respond to touch? (1 Mark)
(b) What is the difference between tropic and nastic movements in plants? (2 Marks)
(c) Name one plant hormone responsible for growth. (1 Mark)
OR
(c) How do tendrils in plants move around a support? (1 Mark)
Ans:
(a) The Touch-Me-Not plant responds to touch by losing water from certain cells, causing its leaves to fold.
(b) Tropic movements are directional and depend on growth (e.g., phototropism), while nastic movements are non-directional and do not depend on growth (e.g., response of Mimosa pudica to touch).
(c) Auxin is a plant hormone that promotes growth.
OR
(c) Tendrils show thigmotropism (response to touch) by growing towards a support, where the side in contact with the support grows slower than the opposite side, causing coiling.
Diya’s uncle was diagnosed with diabetes and was advised to take insulin injections to control his blood sugar levels. Diya was curious about how hormones regulate body functions. Her teacher explained that hormones act as chemical messengers and control various activities in the body.
(a) What is the function of insulin in the human body? (1 Mark)
(b) Explain how the secretion of hormones is regulated in the body. (2 Marks)
(c) Why is iodine necessary in our diet? (1 Mark)
OR
(c) Which hormone is responsible for the "fight or flight" response in humans? (1 Mark)
Ans:
(a) Insulin regulates blood sugar levels by helping cells absorb glucose from the blood.
(b) Hormones are regulated by a feedback mechanism:
(c) Iodine is essential for the synthesis of thyroxin, which regulates metabolism. A lack of iodine causes goitre.
OR
(c) The adrenal gland secretes adrenaline, which prepares the body for emergency situations (fight or flight response).
At a family gathering, Diya observed that her younger cousin was much taller than other children of the same age. Her aunt mentioned that doctors had said it was due to growth hormone imbalance. This made Diya curious about how hormones influence body growth and development.
(a) Which gland is responsible for the secretion of growth hormone? (1 Mark)
(b) What happens when the body produces too much or too little growth hormone? (2 Marks)
(c) How do hormones control puberty in males and females? (1 Mark)
OR
(c) Which hormone regulates blood sugar levels? (1 Mark)
Ans:
(a) The pituitary gland secretes growth hormone.
(b)
(c)
OR
(c) Insulin, secreted by the pancreas, regulates blood sugar levels.
During a science experiment, Rohan placed his hand near a flame and quickly pulled it away. His teacher explained that this response occurred because of the transmission of nerve impulses through neurons. Neurons communicate with each other at special junctions called synapses, where electrical signals are converted into chemical signals.
(a) What is a synapse? (1 Mark)
(b) Explain how nerve impulses are transmitted from one neuron to another. (2 Marks)
(c) Why do nerve impulses travel in only one direction? (1 Mark)
OR
(c) Which part of a neuron receives the information and which part transmits it? (1 Mark)
Ans:
(a) A synapse is a junction between two neurons where the electrical impulse is converted into a chemical signal for transmission.
(b) Transmission of nerve impulses:
(c) The impulse travels in one direction because neurotransmitters are released only at the axon terminals and the receptors are on the next neuron’s dendrites.
OR
(c) The dendrites receive the information, while the axon terminals transmit it.
Aman’s father was diagnosed with diabetes and was advised by the doctor to reduce sugar intake. He was also prescribed insulin injections. Aman learned that insulin is a hormone that regulates blood sugar levels, and its deficiency leads to diabetes.
(a) Which gland secretes insulin? (1 Mark)
(b) How does insulin regulate blood sugar levels? (2 Marks)
(c) What would happen if insulin is not secreted in the right amount? (1 Mark)
OR
(c) Which hormone regulates metabolism and requires iodine for its synthesis? (1 Mark)
Ans:
(a) The pancreas secretes insulin.
(b)
(c) If insulin is not secreted properly, blood sugar levels rise, leading to diabetes, which causes weakness, weight loss, and excessive urination.
OR
(c) The thyroid gland secretes thyroxin, which regulates metabolism and requires iodine.
Neha conducted an experiment where she placed a potted plant near a window. She noticed that over time, the plant’s shoot bent towards the light. Her teacher explained that this response is due to the plant hormone auxin, which controls growth and movement.
(a) What is phototropism? (1 Mark)
(b) How does auxin help in phototropism? (2 Marks)
(c) What is geotropism? Give an example. (1 Mark)
OR
(c) How do roots respond to water availability? (1 Mark)
Ans:
(a) Phototropism is the movement of plant parts towards or away from light.
(b) Auxin accumulates on the shady side of the stem, causing faster cell elongation on that side, making the plant bend towards the light.
(c) Geotropism is the response of plants to gravity. Example: Roots grow downwards (positive geotropism) and shoots grow upwards (negative geotropism).
OR
(c) Roots show hydrotropism, meaning they grow towards water sources.
During a medical check-up, a doctor tapped a small hammer on Sanya’s knee, and her leg moved involuntarily. The doctor explained that this response was due to a reflex action, which is controlled by the spinal cord without involving the brain.
(a) What are involuntary actions? (1 Mark)
(b) How are involuntary actions different from reflex actions? (2 Marks)
(c) Which part of the brain controls involuntary actions like digestion and breathing? (1 Mark)
OR
(c) Why are reflex actions faster than voluntary actions? (1 Mark)
Ans:
(a) Involuntary actions are automatic body functions that occur without conscious control (e.g., digestion, heartbeat).
(b)
(c) The medulla oblongata in the hindbrain controls involuntary actions like breathing, digestion, and heartbeat.
OR
(c) Reflex actions are faster because they do not involve the brain and are processed directly by the spinal cord.
During a health awareness session, the doctor explained that hormones control growth, metabolism, and development. He also mentioned that a deficiency of growth hormone during childhood leads to dwarfism, while its excess causes gigantism.
(a) Which gland secretes the growth hormone? (1 Mark)
(b) What happens if the body produces too much or too little growth hormone? (2 Marks)
(c) Which hormone controls secondary sexual characteristics in females? (1 Mark)
OR
(c) How does adrenaline prepare the body for emergency situations? (1 Mark)
Ans:
(a) The pituitary gland secretes the growth hormone.
(b)
(c) Oestrogen, secreted by the ovaries, controls secondary sexual characteristics in females.
OR
(c) Adrenaline increases heart rate, breathing rate, and energy supply, preparing the body for emergency situations (fight-or-flight response).
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1. What is the role of hormones in the control and coordination of the human body? | ![]() |
2. How do neurons transmit signals in the nervous system? | ![]() |
3. What are the differences between the nervous system and the endocrine system in terms of control and coordination? | ![]() |
4. What is a reflex action, and how does it occur? | ![]() |
5. What are some examples of plant hormones and their functions? | ![]() |