Class 10 Science Chapter 6 Control and Coordination NCERT Solutions 2026 PDF Download
📝 Introduction
Control and Coordination explains how organisms detect changes in their environment and respond to them efficiently. Unlike simple machines, living organisms have complex systems to ensure that movement and growth happen in a controlled manner. In animals, this is achieved by the Nervous System (electrical impulses) and the Endocrine System (chemical hormones). In plants, lacking a nervous system, coordination is achieved solely through chemical means (phytohormones). This chapter covers the structure of neurons, the reflex arc, the human brain, and the various hormones that regulate growth and metabolism.
[Image of Structure of Neuron]🔑 Key Concepts & Formulas
- Neuron: The structural and functional unit of the nervous system. Transmits information via electrical impulses.
- Reflex Arc: The pathway taken by a nerve impulse during a reflex action (Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector).
- Synapse: The gap between two neurons where the electrical signal is converted into a chemical signal (neurotransmitter).
- Human Brain:
- Forebrain (Cerebrum): Thinking, voluntary actions, memory.
- Midbrain: Involuntary actions (pupil size).
- Hindbrain: Cerebellum (Posture/Balance), Medulla (BP, Salivation, Vomiting).
- Plant Hormones:
- Auxins: Growth (cell elongation).
- Gibberellins: Stem growth.
- Cytokinins: Cell division.
- Abscisic Acid: Inhibits growth (wilting).
- Endocrine Glands: Pituitary (Growth Hormone), Thyroid (Thyroxin), Pancreas (Insulin), Adrenal (Adrenaline).
📚 Part 1: NCERT Solutions (In-Text & Exercises)
Q1: What is the difference between a reflex action and walking?
Ans:
- Reflex Action: An involuntary, rapid, and automatic response to a stimulus (e.g., pulling hand from heat). Controlled by the Spinal Cord.
- Walking: A voluntary action initiated by our will. Controlled by the Cerebellum (hindbrain) for balance and the Cerebrum (forebrain) for the decision to walk.
Q2: What happens at the synapse between two neurons?
Ans: At the synapse, the electrical impulse arriving at the nerve ending of one neuron releases certain chemicals (neurotransmitters). These chemicals diffuse across the gap and start a similar electrical impulse in the dendrite of the next neuron.
Q3: Which part of the brain maintains posture and equilibrium of the body?
Ans: The Cerebellum, which is a part of the Hindbrain, is responsible for maintaining the posture and equilibrium (balance) of the body.
Q4: How do we detect the smell of an agarbatti (incense stick)?
Ans: The smell is detected by Olfactory Receptors located in our nose. They send electrical impulses to the sensory area of the Forebrain (Cerebrum), which interprets the signal as the smell of agarbatti based on information stored in memory.
Q5: What is the role of the brain in reflex action?
Ans: In a reflex action, the immediate response is generated by the Spinal Cord to save time. However, the information signal is also sent to the Brain. The brain records this event for future memory but does not control the immediate reaction.
Q6: How does chemical coordination take place in animals?
Ans: It takes place via the Endocrine System. Endocrine glands secrete chemical messengers called Hormones directly into the blood. The blood carries these hormones to specific target organs, where they modify the functions of cells/tissues to coordinate growth, metabolism, and behavior.
Q7: Why is the use of iodised salt advisable?
Ans: Iodine is essential for the Thyroid gland to synthesize the Thyroxin hormone. Thyroxin regulates carbohydrate, protein, and fat metabolism. Deficiency of iodine leads to a disease called Goitre (swollen neck).
Q8: How does our body respond when adrenaline is secreted into the blood?
Ans: Adrenaline prepares the body for a "Fight or Flight" situation:
1. Heart beats faster to supply more oxygen to muscles.
2. Blood is diverted from digestion/skin to skeletal muscles.
3. Breathing rate increases.
This allows the body to deal with emergency situations.
Q9: Why are some patients of diabetes treated by giving injections of insulin?
Ans: Diabetes is caused by a deficiency of the hormone Insulin (secreted by the Pancreas), which is responsible for lowering blood sugar levels. Patients take insulin injections to artificially lower their blood sugar and prevent harmful effects of hyperglycemia.
⚡ Part 2: 15 Extra Practice Questions (PYQ Style)
Short Answer Type Questions
Q1: Draw the structure of a Neuron and label the following: (i) Part where information is acquired (ii) Part through which information travels as an electric impulse.
Ans:
(i) Dendrite: Acquires information.
(ii) Axon: Transmits electrical impulse.
Q2: Define Tropism. Give one example.
Ans: The directional growth movement of a plant part in response to an external stimulus is called Tropism.
Example: Phototropism (Shoot bends towards light).
Q3: What constitutes the Central Nervous System (CNS) and Peripheral Nervous System (PNS)?
Ans:
- CNS: Brain and Spinal Cord.
- PNS: Cranial nerves (from brain) and Spinal nerves (from spinal cord).
Q4: Name the hormone responsible for: (i) Elongation of cells (ii) Inhibiting growth.
Ans:
(i) Auxin (promotes elongation).
(ii) Abscisic Acid (inhibits growth/wilting).
Q5: How does the plant shoot detect light?
Ans: The tip of the shoot produces the hormone Auxin. When light comes from one side, auxin diffuses to the shady side of the shoot. This concentration of auxin stimulates the cells on the shady side to grow longer, causing the shoot to bend towards the light.
Long Answer Type Questions
Q6: Explain the structure and function of the human brain.
Ans:
- Forebrain (Cerebrum): Largest part. Controls voluntary actions, sensory perception, learning, and memory.
- Midbrain: Connects forebrain and hindbrain. Controls involuntary reflexes like change in pupil size.
- Hindbrain:
- Cerebellum: Balance and posture.
- Medulla: Involuntary actions like BP, vomiting, salivation.
- Pons: Respiration regulation.
Q7: What is a Feedback Mechanism? Explain with an example involving Insulin.
Ans: A mechanism that regulates the timing and amount of hormone released is called a Feedback Mechanism.
Example:
1. Blood sugar rises → Detected by Pancreas → More Insulin secreted.
2. Blood sugar falls → Detected by Pancreas → Insulin secretion reduced.
This ensures hormone levels are precise.
Q8: Trace the sequence of events in a Reflex Arc when you touch a hot object.
Ans:
1. Stimulus: Heat touches the skin.
2. Receptor: Thermoreceptors in skin detect heat.
3. Sensory Neuron: Carries impulse to Spinal Cord.
4. Relay Neuron: Connects sensory to motor neuron in Spinal Cord.
5. Motor Neuron: Carries impulse to muscle.
6. Effector: Muscle in arm contracts.
7. Response: Hand is pulled back.
Competency Based Questions
Q9: Why are electrical impulses not enough for coordination in multi-cellular organisms? Why is chemical coordination needed?
Ans:
1. Electrical impulses reach only those cells connected by nervous tissue (not all cells).
2. Once an impulse is generated, the cell takes time to reset before generating a new one (cannot be continuous).
Chemical coordination (Hormones) solves this by diffusing to all cells and providing a steady, persistent signal.
Q10: A person has a swollen neck and feels lethargic. Which mineral is likely deficient in their diet, and which gland is affected?
Ans: The person is likely suffering from Goitre.
Mineral deficient: Iodine.
Gland affected: Thyroid Gland. The gland swells in an attempt to absorb more iodine from the blood to produce Thyroxin.
Q11: Distinguish between Nastic movements and Tropic movements.
Ans:
- Tropic: Directional movement (growth) dependent on the direction of stimulus (e.g., Shoot bending to light).
- Nastic: Non-directional movement independent of the stimulus direction (e.g., Drooping of Touch-me-not leaves).
Q12: Which gland is called the "Master Gland" and why?
Ans: The Pituitary Gland. It produces hormones (like Growth Hormone) that control the secretions of other endocrine glands (like Thyroid, Adrenal, Testes/Ovaries).
Q13: Name the receptor for: (i) Taste (ii) Smell.
Ans:
(i) Taste: Gustatory receptors (Tongue).
(ii) Smell: Olfactory receptors (Nose).
Q14: Explain the movement in the 'Touch-me-not' (Mimosa pudica) plant.
Ans: It is a Thigmonastic movement (response to touch). When touched, the plant cells change the amount of water in them (turgor pressure), causing them to shrink or swell. This change results in the folding up and drooping of leaves. It is not growth-dependent.
Q15: What is the function of the cerebrospinal fluid (CSF)?
Ans: CSF fills the space between the brain/spinal cord and their protective membranes (meninges). It provides shock absorption, protecting the delicate nervous tissue from mechanical injury.