CBSE Class 10 Science Control and Coordination MCQs Set 05

Answer: (c) Hypothalamus. The hypothalamus regulates body temperature and urges such as hunger, thirst and sleep.

Teacher's Note:
1. The hypothalamus lies in the forebrain and also controls the pituitary gland.
2. Remember it as the body's thermostat.

Answer: (b) cerebellum. The cerebellum coordinates voluntary movements, posture and balance.

Teacher's Note:
1. Actions like walking in a straight line or picking up a pencil depend on it.
2. It is part of the hind-brain.

Answer: (c) medulla oblongata. The medulla in the hind-brain controls involuntary actions of internal organs.

Teacher's Note:
1. Damage to the medulla can stop breathing and heartbeat.
2. It is therefore a life-critical centre.

Answer: (a) fore-brain. The fore-brain (mainly the cerebrum) handles thinking, memory, hearing, smell, sight and voluntary action.

Teacher's Note:
1. It also contains centres for hunger.
2. The cerebrum is much larger in humans than in other animals.

Answer: (a) a synapse. A synapse is the functional junction where a chemical signal crosses from one neuron to the next.

Teacher's Note:
1. Impulses are electrical inside a neuron but chemical across the synapse.
2. This is why synaptic transmission is slightly slower.

Answer: (a) receptor → sensory neuron → spinal cord → motor neuron → effector. The impulse travels from the receptor along the sensory neuron to the spinal cord, then along the motor neuron to the effector.

Teacher's Note:
1. In a reflex the spinal cord, not the brain, is the main processing centre.
2. This makes the response very fast.

Answer: (b) Withdrawing the hand from a hot object. Pulling the hand away from heat is automatic, rapid and processed in the spinal cord.

Teacher's Note:
1. Reflexes do not need thinking.
2. Writing and riding are voluntary actions controlled by the brain.

Answer: (c) motor neuron. Motor neurons carry the response from the central nervous system to the effector.

Teacher's Note:
1. Sensory neurons do the opposite and carry information inwards.
2. Relay neurons connect the two inside the spinal cord.

Answer: (b) axon. The axon carries the electrical impulse away from the cell body towards the next cell.

Teacher's Note:
1. Dendrites acquire the information instead.
2. Remember: Dendrite Delivers in, Axon Away.

Answer: (c) retina. Rods and cones, the light-sensitive cells, are found in the retina.

Teacher's Note:
1. The retina converts light into electrical signals.
2. These pass to the brain along the optic nerve.

Answer: (b) olfactory receptors. Olfactory receptors in the nose detect chemicals in the air and send signals to the fore-brain.

Teacher's Note:
1. Gustatory receptors are those on the tongue for taste.
2. Both are chemoreceptors.

Answer: (a) Pancreas – insulin. Insulin is secreted by the pancreas and lowers blood sugar.

Teacher's Note:
1. Thyroxine comes from the thyroid and adrenaline from the adrenal glands.
2. Oestrogen is made by the ovary.

Answer: (b) thyroxine. Thyroxine contains iodine and regulates carbohydrate, protein and fat metabolism.

Teacher's Note:
1. Lack of iodine can cause goitre, a swelling in the neck.
2. Hence the use of iodised salt.

Answer: (c) Adrenaline. Adrenaline from the adrenal glands triggers the fight-or-flight response.

Teacher's Note:
1. It diverts blood to the muscles and raises blood sugar.
2. The effect starts within seconds.

Answer: (b) growth hormone. Growth hormone from the pituitary controls growth of the body.

Teacher's Note:
1. The pituitary is called the master gland.
2. Its hormones regulate several other glands.

Answer: (a) insulin. Insulin helps cells and the liver take up glucose; lack of insulin leads to diabetes.

Teacher's Note:
1. Insulin is released when blood sugar rises.
2. This is a feedback mechanism.

Answer: (b) testosterone. Testosterone from the testes causes changes such as a deeper voice and facial hair at puberty.

Teacher's Note:
1. In females, oestrogen does a similar job.
2. These changes are signs of puberty.

Answer: (c) Cytokinin. Cytokinins promote cell division and are abundant in fruits and seeds.

Teacher's Note:
1. Auxin and gibberellin mainly promote cell elongation.
2. Abscisic acid is a growth inhibitor.

Answer: (d) abscisic acid. Abscisic acid is a growth inhibitor that also closes stomata under water stress.

Teacher's Note:
1. It has the opposite effect to growth-promoting hormones.
2. It helps plants survive dry conditions.

Answer: (a) auxin. Auxin collects on the shaded side and makes those cells grow longer, so the shoot bends towards light.

Teacher's Note:
1. This response is called phototropism.
2. It is a growth movement, not a nastic one.

Answer: (b) positive geotropism. Roots grow towards gravity, which is positive geotropism.

Teacher's Note:
1. Shoots show negative geotropism by growing upwards.
2. Roots also respond to water (hydrotropism).

Answer: (c) chemotropism. The pollen tube grows in response to chemicals released by the ovule.

Teacher's Note:
1. Chemotropism is growth guided by chemicals.
2. Tropic movements are directional, unlike nastic movements.

Answer: (b) a non-directional movement due to changes in water in cells. Cells at the leaf base lose water and shrink, so the leaf droops; the movement is independent of the direction of touch.

Teacher's Note:
1. Plants have no nervous system.
2. They use electrical-chemical signals and changes in cell turgor.

Answer: (b) cells on the side away from the support grow faster. Auxin makes the cells on the far side grow faster, so the tendril curls around the support.

Teacher's Note:
1. This growth response to contact is called thigmotropism.
2. The side touching the support grows less.

Answer: (c) ethylene. Ethylene is a gaseous plant hormone that promotes fruit ripening.

Teacher's Note:
1. Traders use it to ripen raw fruits.
2. Gaseous hormones can spread to nearby fruits as well.