Control and Coordination — Class 10 Biology NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 10 Biology chapter "Control and Coordination" — 9 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 10 Biology chapter "Control and Coordination" — 9 important questions with detailed answers for CBSE board…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
NCERT Solutions for Class 10 Biology — Control and Coordination. Step-by-step answers to all 9 textbook questions from this chapter, written for CBSE board preparation and free to use.
Control and Coordination — All 9 Questions Solved
Q1. Define reflex action. Draw a labeled diagram of a reflex arc and explain how it works.
Reflex action is a quick, involuntary response to a stimulus that does not involve the brain. It happens automatically without conscious thought.
Reflex arc components (in order of response):
1. Receptor (e.g., sensory nerve ending in skin) - detects stimulus
2. Sensory neuron (afferent neuron) - carries signal to spinal cord
3. Spinal cord - contains relay neuron connecting sensory to motor neuron
4. Motor neuron (efferent neuron) - carries signal from spinal cord to muscle
5. Effector (muscle) - contracts causing response
How reflex arc works:
- When you touch a hot object, sensory receptor detects heat
- Sensory neuron sends signal to spinal cord
- In spinal cord, synapse between sensory and motor neuron
- Motor neuron activates muscle in arm
- Hand jerks away from heat automatically
- Signal reaches brain only after reflex occurs
Advantage: Reflex actions are faster than conscious responses because they bypass the brain, protecting body from injury.
Q2. What is the structure and function of a neuron? How do neurons transmit signals?
Structure of a neuron (nerve cell):
1. Dendrites - short branching extensions that receive signals from other neurons
2. Cell body (soma) - contains nucleus; integrates signals
3. Axon - long extension that transmits signals away from cell body
4. Axon terminals - branches at end of axon that form synapses with other neurons
Function: Neurons transmit electrical and chemical signals throughout body for communication and coordination.
Signal transmission:
1. Resting potential - neuron at rest has negative charge inside and positive outside
2. Stimulus causes depolarization - Na+ ions enter axon, making inside positive
3. Action potential propagates - wave of depolarization travels along axon
4. Repolarization occurs - K+ ions leave, restoring negative charge inside
5. At synapse - axon terminal releases neurotransmitters (chemical signals)
6. Neurotransmitters cross synaptic cleft and bind to receptors on next neuron
7. This may generate new action potential in next neuron
Synapses are one-way; signals travel from axon terminal of one neuron to dendrite of next neuron.
Q3. Compare the nervous system and endocrine system. How do they coordinate body functions?
Nervous system:
- Uses electrical signals (action potentials)
- Transmission through neurons
- Very fast (milliseconds)
- Effects are localized and short-term
- Composed of brain, spinal cord, and nerves
- Divisions: Central nervous system (brain and spinal cord) and Peripheral nervous system (somatic and autonomic nerves)
Endocrine system:
- Uses chemical signals (hormones)
- Transmission through blood
- Slower (seconds to hours)
- Effects are widespread and long-term
- Composed of glands (pituitary, thyroid, pancreas, adrenal, gonads, etc.)
- Hormones regulate metabolism, growth, reproduction, stress response
Coordination:
- Nervous system provides rapid responses to immediate stimuli (e.g., reflex, muscle contraction)
- Endocrine system maintains long-term regulation (e.g., growth, metabolism, reproduction)
- Both systems work together: brain controls pituitary gland which controls other endocrine glands
- Example: fight-or-flight response involves both nervous system (rapid) and adrenal glands releasing adrenaline (hormonal)
Together they maintain homeostasis and coordinate all body functions.
Q4. What are plant hormones (phytohormones)? Name the major ones and their functions.
Plant hormones (phytohormones) are chemical messengers produced in small amounts that regulate plant growth and development.
Major plant hormones and functions:
1. Auxins (e.g., Indole Acetic Acid):
- Promote cell elongation (growth)
- Promote root development
- Cause phototropism (bending towards light)
- Cause geotropism (roots grow downward, shoots upward)
- Inhibit abscission (dropping of leaves)
2. Gibberellins:
- Promote stem elongation
- Break seed dormancy
- Promote flowering
- Increase fruit size
3. Cytokinins:
- Promote cell division
- Delay senescence (aging)
- Promote shoot development
4. Ethylene:
- Promotes fruit ripening
- Promotes flowering (in some plants)
- Causes senescence and abscission
5. Abscisic acid (ABA):
- Closes stomata during stress (water stress)
- Inhibits seed germination
- Promotes senescence
Plant hormones work together to coordinate growth, development, and response to environment.
Q5. What is tropism? Explain phototropism and geotropism with examples.
Tropism is the directional growth movement of a plant in response to an external stimulus. The plant grows towards or away from the stimulus.
Phototropism (response to light):
- Definition: Growth movement in response to light direction
- Mechanism: Auxin hormone accumulates on shaded side of stem
- Result: Shaded side grows more, causing stem to bend towards light
- Adaptive value: Maximizes light exposure for photosynthesis
- Examples: Sunflower tracking the sun, seedlings bending towards window light
Geotropism (response to gravity):
- Definition: Growth movement in response to gravitational pull
- Two types:
a) Positive geotropism - growth towards gravity
Example: Root growth downward into soil
Mechanism: Auxin accumulates at bottom of root; root cells at bottom less sensitive to auxin, so they grow less, causing root to bend downward
b) Negative geotropism - growth against gravity
Example: Shoot growth upward
Mechanism: Auxin accumulates at bottom of shoot; shoot cells at bottom grow more, causing shoot to bend upward
- Adaptive value: Roots reach water and nutrients in soil; shoots reach sunlight
Both tropisms are growth movements and are slower than nervous system responses.
Q6. What is the human nervous system? Describe its divisions and functions.
The human nervous system is the body's communication and control system. It detects stimuli and coordinates appropriate responses.
Divisions of nervous system:
1. Central Nervous System (CNS):
a) Brain - controls all functions, processes information
- Cerebrum: conscious thought, sensation, voluntary movement
- Cerebellum: balance and coordination
- Medulla: involuntary functions (breathing, heartbeat)
b) Spinal cord - relay between brain and body; controls reflex arcs
2. Peripheral Nervous System (PNS) - nerves connecting CNS to rest of body:
a) Somatic nervous system - voluntary control of skeletal muscles and sensory input
b) Autonomic nervous system - involuntary control of internal organs:
- Sympathetic: increases heart rate, pupil dilation (fight-or-flight)
- Parasympathetic: decreases heart rate, promotes digestion (rest-and-digest)
Functions:
- Sensory function: collects information from environment via receptors
- Integration: brain and spinal cord process information
- Motor function: sends commands to muscles and glands
- Maintains homeostasis: adjusts body functions to maintain stable internal environment
Q7. Name the major endocrine glands in the human body and the hormones they produce.
Major endocrine glands and hormones:
1. Pituitary gland (master gland):
- Anterior pituitary: Growth hormone (GH), Thyroid-stimulating hormone (TSH), Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Adrenocorticotropic hormone (ACTH), Prolactin
- Posterior pituitary: Antidiuretic hormone (ADH), Oxytocin
2. Thyroid gland:
- Thyroxine (T4) and Triiodothyronine (T3) - increase metabolic rate
- Calcitonin - lowers blood calcium
3. Parathyroid glands:
- Parathormone (PTH) - raises blood calcium
4. Adrenal glands:
- Adrenal cortex: Glucocorticoids (cortisol), Mineralocorticoids (aldosterone), Androgens
- Adrenal medulla: Adrenaline (epinephrine), Noradrenaline (norepinephrine) - fight-or-flight
5. Pancreas:
- Insulin - lowers blood glucose
- Glucagon - raises blood glucose
6. Gonads:
- Testis: Testosterone - male sex characteristics
- Ovary: Estrogen and Progesterone - female sex characteristics
7. Thymus gland:
- Thymosin - immune function
8. Pineal gland:
- Melatonin - regulates sleep-wake cycle
Q8. What is homeostasis? Explain how the nervous and endocrine systems work together to maintain blood glucose levels.
Homeostasis is the maintenance of a stable internal environment despite external changes. The body maintains constant temperature, pH, water content, and glucose levels.
Blood glucose regulation:
Normal blood glucose: 70-100 mg/dL
When blood glucose is HIGH (after eating):
1. Pancreatic beta cells detect high glucose
2. Pancreas releases insulin hormone
3. Insulin allows glucose to enter cells from blood
4. Liver converts excess glucose to glycogen (storage)
5. Muscles take up glucose for respiration
6. Blood glucose returns to normal
When blood glucose is LOW (between meals, during exercise):
1. Pancreatic alpha cells detect low glucose
2. Pancreas releases glucagon hormone
3. Glucagon signals liver to break down glycogen into glucose
4. Adrenaline (from adrenal medulla) also released during stress/exercise
5. Glucose released into bloodstream
6. Blood glucose returns to normal
Nervous system involvement:
- Nerves sense low blood glucose
- Signals sent to pancreas and adrenal medulla
- Hormones released in response
Endocrine system involvement:
- Hormones (insulin, glucagon, adrenaline) directly regulate glucose level
- Works slowly but has long-lasting effects
Together, these systems maintain blood glucose homeostasis through negative feedback control.
Q9. Explain how the human eye detects and processes light to form images. Describe the path of light through the eye.
Structure and function of human eye:
Path of light through eye:
1. Light enters through cornea - first refraction occurs here
2. Passes through aqueous humor - transparent fluid
3. Enters iris - controls pupil size (dilates in dim light, constricts in bright light)
4. Passes through lens - adjusts shape (accommodation) to focus light on retina
5. Passes through vitreous humor - transparent gel filling eyeball
6. Strikes retina - light-sensitive tissue at back of eye
Structure of retina:
- Contains photoreceptor cells: rod cells (black and white vision, low light) and cone cells (color vision, bright light)
- Rods: ~120 million, sensitive to dim light, not sensitive to color
- Cones: ~6 million, sensitive to bright light, three types detect red, green, blue
Light detection and signal processing:
1. Light activates photopigments in rod and cone cells
2. This triggers electrical signal in photoreceptor
3. Signal passes through bipolar cells
4. Signal reaches ganglion cells
5. Ganglion axons form optic nerve
6. Optic nerve carries signal to visual cortex in brain
7. Brain interprets signal as image
Accommodation (focusing):
- Ciliary muscles contract: lens becomes thicker for near vision
- Ciliary muscles relax: lens becomes thinner for far vision
- This allows sharp images on retina at any distance
Control and Coordination — Practice MCQs with Answers
Attempt these 20 multiple-choice questions after working through the solutions above. Each carries the correct option and the reasoning behind it, so a wrong answer tells you which idea to revisit.
MCQ 1. What is the functional unit of the nervous system?
- A. Nephron
- B. Neuron
- C. Axon
- D. Dendrite
Answer: B. Neuron — A neuron is the structural and functional unit of the nervous system responsible for transmitting nerve impulses throughout the body.
MCQ 2. Which part of the brain is primarily responsible for maintaining posture and balance of the body?
- A. Cerebrum
- B. Cerebellum
- C. Medulla oblongata
- D. Hypothalamus
Answer: B. Cerebellum — The cerebellum, located at the back of the brain, coordinates voluntary movements, maintains balance, and refines motor skills.
MCQ 3. A person suffers from a condition where their blood sugar levels are consistently high due to insufficient insulin production. Which endocrine gland is directly affected in this condition?
- A. Thyroid gland
- B. Adrenal gland
- C. Pancreas
- D. Pituitary gland
Answer: C. Pancreas — The pancreas produces insulin, a hormone essential for regulating blood sugar levels. Insufficient insulin leads to high blood sugar, a condition known as diabetes.
MCQ 4. The microscopic gap between two adjacent neurons where nerve impulses are transmitted is called a:
- A. Dendrite
- B. Axon
- C. Synapse
- D. Myelin sheath
Answer: C. Synapse — A synapse is the specialized junction between two neurons where electrical or chemical signals are transmitted from one neuron to the next.
MCQ 5. Which of the following plant hormones primarily promotes cell division and delays the aging of leaves?
- A. Auxin
- B. Gibberellin
- C. Cytokinin
- D. Abscisic acid
Answer: C. Cytokinin — Cytokinins are plant hormones that play a crucial role in promoting cell division, differentiation, and delaying senescence (aging) in plants.
MCQ 6. If the secretion of growth hormone is deficient during childhood, what condition is likely to occur?
- A. Gigantism
- B. Acromegaly
- C. Dwarfism
- D. Goitre
Answer: C. Dwarfism — Insufficient secretion of growth hormone during the formative years of childhood leads to stunted growth, a condition medically termed dwarfism.
MCQ 7. Which part of the neuron is responsible for receiving information or signals from other neurons?
- A. Axon
- B. Cell body
- C. Dendrite
- D. Nerve ending
Answer: C. Dendrite — Dendrites are short, branched extensions of a neuron that act as primary receivers of signals from other neurons.
MCQ 8. Which of these is an example of a reflex action primarily controlled by the spinal cord without direct involvement of the brain?
- A. Speaking
- B. Walking
- C. Blinking
- D. Knee-jerk reflex
Answer: D. Knee-jerk reflex — The knee-jerk reflex is a classic example of a spinal reflex, where sensory input leads to a motor response via the spinal cord, bypassing direct brain processing.
MCQ 9. The 'fight or flight' response in humans is primarily regulated by which hormone?
- A. Thyroxine
- B. Insulin
- C. Adrenaline
- D. Estrogen
Answer: C. Adrenaline — Adrenaline, secreted by the adrenal glands, prepares the body for stressful situations by increasing heart rate, blood pressure, and energy supply, triggering the 'fight or flight' response.
MCQ 10. The bending of a plant stem towards a light source is an example of:
- A. Geotropism
- B. Hydrotropism
- C. Phototropism
- D. Thigmotropism
Answer: C. Phototropism — Phototropism is the growth movement of a plant in response to light, typically seen as stems bending towards the light source.
MCQ 11. Which endocrine gland is often referred to as the 'master gland' because it controls the functions of many other endocrine glands?
- A. Thyroid gland
- B. Pituitary gland
- C. Adrenal gland
- D. Pancreas
Answer: B. Pituitary gland — The pituitary gland, located at the base of the brain, secretes hormones that regulate the activity of other endocrine glands, earning it the title 'master gland'.
MCQ 12. A plant hormone that inhibits growth, promotes dormancy in buds and seeds, and causes wilting of leaves during stress is:
- A. Auxin
- B. Gibberellin
- C. Cytokinin
- D. Abscisic acid
Answer: D. Abscisic acid — Abscisic acid (ABA) is a plant hormone that acts as a growth inhibitor, playing a significant role in plant responses to stress, dormancy, and wilting.
MCQ 13. Which of the following is an involuntary action, meaning it occurs without conscious control?
- A. Reading a book
- B. Cycling a bicycle
- C. Heartbeat
- D. Writing a letter
Answer: C. Heartbeat — Involuntary actions, like the beating of the heart, breathing, and digestion, are regulated by the autonomic nervous system and occur without conscious thought.
MCQ 14. Damage to which part of the brain would most severely affect a person's ability to coordinate fine motor skills, such as playing a musical instrument or precise hand movements?
- A. Medulla oblongata
- B. Cerebellum
- C. Hypothalamus
- D. Cerebrum
Answer: B. Cerebellum — The cerebellum is crucial for coordinating voluntary movements, maintaining balance, and fine-tuning motor activities, making it essential for skilled tasks.
MCQ 15. A patient experiences tremors, rigidity, slow movements, and difficulty with balance. Which neurotransmitter deficiency is most likely associated with these symptoms?
- A. Acetylcholine
- B. Dopamine
- C. Serotonin
- D. GABA
Answer: B. Dopamine — The symptoms described are characteristic of Parkinson's disease, which is primarily caused by the degeneration of dopamine-producing neurons in the brain, affecting motor control.
MCQ 16. The main function of the sensory neuron in a reflex arc is to:
- A. Carry signals from the brain to muscles
- B. Carry signals from receptors to the central nervous system
- C. Process information within the central nervous system
- D. Release hormones into the bloodstream
Answer: B. Carry signals from receptors to the central nervous system — Sensory neurons (afferent neurons) transmit nerve impulses from sensory receptors in the body towards the central nervous system (brain and spinal cord).
MCQ 17. Which plant hormone is a gaseous compound primarily responsible for fruit ripening and senescence?
- A. Auxin
- B. Gibberellin
- C. Ethylene
- D. Cytokinin
Answer: C. Ethylene — Ethylene is a unique gaseous plant hormone that plays a critical role in the ripening of fruits and the aging processes of plants.
MCQ 18. Deficiency of which hormone leads to 'Cretinism' in children and 'Myxedema' in adults?
- A. Growth Hormone
- B. Thyroxine
- C. Adrenaline
- D. Insulin
Answer: B. Thyroxine — Thyroxine, produced by the thyroid gland, regulates metabolism. Its deficiency leads to cretinism (severe physical and mental retardation) in children and myxedema in adults.
MCQ 19. The growth of plant roots downwards into the soil, in response to gravity, is an example of:
- A. Phototropism
- B. Geotropism
- C. Hydrotropism
- D. Chemotropism
Answer: B. Geotropism — Geotropism (or gravitropism) is the growth of a plant in response to gravity. Roots exhibit positive geotropism by growing downwards.
MCQ 20. The function of gustatory receptors in humans is to detect:
- A. Smell
- B. Touch
- C. Taste
- D. Sound
Answer: C. Taste — Gustatory receptors are specialized sensory receptors located primarily on the tongue that are responsible for detecting different tastes.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.