Class 10 Science Chapter 6: Important & Previous Year Questions – Bihar Board

Correct answer: (D) Cerebrum

Thinking, memory and voluntary actions are the work of the cerebrum, the main part of the fore-brain (lesson 3, Fig. 6.3).

Correct answer: (D) Geotropism

Roots grow down in the direction of gravity — geotropism (lesson 5, Fig. 6.6). The shoot grows up, against gravity.

Correct answer: (C) Ovary

Oestrogen comes from the ovary and controls the development of female sex organs and the menstrual cycle (lesson 7, Table 6.1). The testis secretes testosterone.

Main functions of the nervous system:

• Receiving information: receptors (eye, ear, nose, tongue, skin) pick up changes in the surroundings;
• Conduction: this information travels as electrical impulses to the brain and spinal cord;
• Processing and decision: the brain interprets it, thinks and remembers;
• Sending orders: motor nerves carry commands to muscles and glands (effectors);
• Reflex action: in danger, the spinal cord replies at once;
• Control of involuntary actions: blood pressure, salivation, vomiting (medulla), balance of the body (cerebellum).

👉 In this way the nervous system brings about control and coordination of all organs.

Correct answer: (D) Cytokinin

Cytokinin is a plant hormone — it promotes cell division (lesson 6). The other three are animal hormones. This is also NCERT exercise Q1.

Correct answer: (C) Ethylene

Ethylene is a gaseous plant hormone that ripens fruits. NCERT names auxin, gibberellins, cytokinins and abscisic acid; this board question asks about ethylene separately (lesson 6).

Correct answer: (A) 12 pairs

12 pairs of cranial nerves arise from the brain and 31 pairs of spinal nerves from the spinal cord; together they form the peripheral nervous system (lesson 3).

Correct answer: (C) Adrenal

Adrenaline from the adrenal gland makes the heart beat faster and contracts muscles around small arteries — blood pressure rises (lesson 7). (Among involuntary controls the medulla also looks after blood pressure — lesson 3.)

Neurotransmitters are chemicals released at the end of the axon of a neuron.

• The electrical impulse reaches the axon end and sets off the release of these chemicals;
• they cross the synapse (the gap between two neurons);
• they start a new electrical impulse in the dendrite of the next neuron.

👉 In the same way the impulse is passed from a neuron to a muscle or gland (Fig. 6.1).