Control & Coordination Topic Hub

Control & Coordination — Class 10 Notes

CBSE 2027 — dates, rules and official papers →
Biology · Ch 6Class 10 · CBSE 2026–27High weightage

Control and Coordination

What the board actually asks: label-and-explain diagrams (the neuron, the reflex arc, the human brain and the endocrine glands), the reflex-action pathway traced step-by-step, comparison questions (reflex vs voluntary action, nervous vs hormonal control, plant movement by touch vs by growth), the plant and animal hormones with their glands and functions (Table 6.1), and short why/how reasoning - a diagram-rich chapter where most marks reward the exact NCERT terms.

NCERT VERBATIM sourced, word-for-wordAUTHORED LazyTopper teaching scaffolding
The Big Idea AUTHORED

Living bodies stay coordinated in two ways - fast electrical nerve signals and slower chemical hormones.

A multicellular body must recognise changes around it and respond with just the right action. Animals do this with a nervous system that carries information as electrical impulses and with hormones carried in the blood; plants, having no nerves or muscles, rely on changes in water content and on hormones that direct their growth. In Class 10 this chapter is examined mainly through labelled diagrams and step-by-step explanations, so most marks reward the exact NCERT terms and correctly labelled structures.

Formulae
Neuron path
Dendrite (receives) to cell body to axon to nerve ending; the gap to the next cell is the synapse
Reflex arc
Receptor to sensory neuron to spinal cord (relay) to motor neuron to effector muscle
Brain regions
Fore-brain - thinking, senses, voluntary action, hunger; mid-brain and hind-brain - involuntary; cerebellum - posture and balance; medulla - blood pressure, salivation, vomiting
Plant tropisms
Phototropism (light), geotropism (gravity), hydrotropism (water), chemotropism (chemicals)
Plant hormones
Auxin - elongation and bending; gibberellin - stem growth; cytokinin - cell division; abscisic acid - inhibits growth (wilting)
Animal hormones (Table 6.1)
Growth hormone - pituitary; thyroxin - thyroid (needs iodine); insulin - pancreas (blood sugar); adrenaline - adrenal gland; testosterone - testes; oestrogen - ovaries
Definitions the board rewards NCERT VERBATIM

State these in NCERT’s exact words

Receptors
NCERT verbatim — memorise this exact wording· Ch 6,
“These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on.”
What it means: Specialised nerve-cell tips in the sense organs that detect a particular kind of stimulus - gustatory receptors detect taste, olfactory receptors detect smell.
Nervous tissue
NCERT verbatim — memorise this exact wording· Ch 6,
“Nervous tissue is made up of an organised network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.”
What it means: The tissue built from neurons that carries information rapidly, as electrical impulses, from one part of the body to another.
Reflex arc
NCERT verbatim — memorise this exact wording· Ch 6,
“Such a connection is commonly called a reflex arc.”
What it means: The short nerve pathway - receptor to sensory neuron to spinal cord to motor neuron to effector - that gives a quick automatic response without waiting for the brain to think.
Central nervous system
NCERT verbatim — memorise this exact wording· Ch 6,
“The brain and spinal cord constitute the central nervous system.”
What it means: The brain plus the spinal cord - the main coordinating centre that receives information from all parts of the body and integrates it.
Cerebellum
NCERT verbatim — memorise this exact wording· Ch 6,
“These are possible due to a part of the hind-brain called the cerebellum. It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.”
What it means: The part of the hind-brain that fine-tunes voluntary movements and keeps the body balanced - it lets you walk in a straight line, ride a bicycle or pick up a pencil.
Phototropism
NCERT verbatim — memorise this exact wording· Ch 6,
“So, in two different kinds of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.”
What it means: Directional growth of a plant part in response to light - the shoot grows towards it (positive), the root grows away from it (negative).
Auxin
NCERT verbatim — memorise this exact wording· Ch 6,
“When growing plants detect light, a hormone called auxin, synthesised at the shoot tip, helps the cells to grow longer.”
What it means: A plant hormone made at the shoot tip that makes cells elongate; by collecting on the shady side of the shoot it bends the shoot towards light.
Adrenaline
NCERT verbatim — memorise this exact wording· Ch 6,
“This is done in many animals, including human beings, using a hormone called adrenaline that is secreted from the adrenal glands.”
What it means: The fight-or-flight hormone from the adrenal glands - it makes the heart beat faster, raises the breathing rate and diverts blood to the skeletal muscles to ready the body for action.
Key terms — NCERT verbatim (state word-for-word)
Synapse
These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. (Ch 6, )
Peripheral nervous system
The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord. (Ch 6, )
Medulla
All these involuntary actions including blood pressure, salivation and vomiting are controlled by the medulla in the hind-brain. (Ch 6, )
Geotropism
This upward and downward growth of shoots and roots, respectively, in response to the pull of earth or gravity is, obviously, geotropism. (Ch 6, )
Abscisic acid
Abscisic acid is one example of a hormone which inhibits growth. Its effects include wilting of leaves. (Ch 6, )
Thyroxin
Iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. (Ch 6, )
Insulin
This is a hormone which is produced by the pancreas and helps in regulating blood sugar levels. (Ch 6, )
Feedback mechanism
The timing and amount of hormone released are regulated by feedback mechanisms. (Ch 6, )
Must-know concepts AUTHORED FRAMING

…and where they’re tested

The neuron and the nerve impulse
Receptors in the sense organs pick up a stimulus at the dendritic tip of a neuron; this sets off an electrical impulse that travels dendrite to cell body to axon. At the axon end the impulse releases chemicals that cross the synapse to start a fresh impulse in the next neuron (or in a muscle or gland).
NCERT Fig 6.1(a)Structure of a neuron
The nerve cell - dendrites (receive information) around the cell body with its nucleus, the long axon that carries the impulse, ending in the nerve endings that pass it on.
5-mark: draw and label a neuron and explain its function; what happens at the synapse between two neurons.
Reflex action and the reflex arc
A reflex is a quick, automatic response to a stimulus. Because conscious thinking would be too slow, the sensory nerve is connected to the motor nerve in the spinal cord, forming a reflex arc: receptor to sensory neuron to spinal cord (relay) to motor neuron to effector. The information still travels on to the brain, but the response does not wait for it.
NCERT Fig 6.2Reflex arc
The pathway of a reflex - heat/pain receptors in the skin, the sensory neuron to the spinal cord (CNS), the relay and motor neurons, and the effector muscle in the arm; the message also travels on to the brain.
5-mark: what is a reflex arc; trace a reflex action; how are reflex actions different from voluntary and involuntary actions.
The human brain and its protection
The brain has three regions - fore-brain (main thinking part; sensory areas, voluntary motor control, and a hunger centre), mid-brain and hind-brain. Involuntary actions such as blood pressure, salivation and vomiting are controlled by the medulla; posture, balance and precision of voluntary movement are controlled by the cerebellum. The brain sits in a bony box (cranium) cushioned by fluid, and the vertebral column protects the spinal cord.
NCERT Fig 6.3Human brain
Sectional view - fore-brain (cerebrum) inside the cranium, mid-brain, and the hind-brain parts (pons, medulla, cerebellum) leading to the spinal cord; the hypothalamus and pituitary gland are also labelled.
5-mark: label the human brain and give the functions of cerebrum, cerebellum and medulla; how are the brain and spinal cord protected.
Coordination in plants - two kinds of movement
Plants have neither nerves nor muscles, yet they respond. Some movements are immediate and independent of growth - the sensitive plant (touch-me-not) folds its leaves by changing the amount of water in its cells, so they swell or shrink. Other movements are directional and caused by growth (tropisms), and are much slower.
NCERT Fig 6.6Plant showing geotropism
A potted plant laid on its side - the shoot turns upward, away from gravity (negatively geotropic) while the root turns downward, towards gravity (positively geotropic).
3-mark: how is the movement of the sensitive plant different from the movement of a shoot towards light; how do plants respond without a nervous system.
Tropisms and plant hormones
Directional growth movements are named after the trigger: phototropism (light), geotropism (gravity), hydrotropism (water) and chemotropism (chemicals). Plant hormones coordinate this: auxin (made at the shoot tip) causes elongation and bending towards light, gibberellins help stem growth, cytokinins promote cell division (abundant in fruits and seeds), and abscisic acid inhibits growth and causes wilting.
NCERT Fig 6.5Response of the plant to the direction of light
A germinated seedling in a flask inside a box open towards a window - the shoot bends towards the light while the roots grow away from it (phototropism).
3-mark: define phototropism and geotropism; name plant hormones and their functions; how does auxin make a shoot bend towards light.
Hormones and the endocrine system in animals
Animal hormones are secreted by endocrine glands directly into the blood and act on target organs. Adrenaline (adrenal glands) prepares the body for fight-or-flight; thyroxin (thyroid, needs iodine) regulates metabolism, and its deficiency causes goitre; insulin (pancreas) regulates blood sugar, and its deficiency causes diabetes; growth hormone (pituitary) controls growth, and its deficiency in childhood causes dwarfism; testosterone and oestrogen bring about the changes of puberty. A feedback mechanism keeps each hormone at the right level.
NCERT Fig 6.7Endocrine glands in human beings (a) male, (b) female
The endocrine glands and their positions - hypothalamus, pineal and pituitary glands, thyroid and parathyroid glands, thymus, pancreas, adrenal glands, and the testis (male) or ovaries and uterus (female).
3-5 mark: match hormone-gland-function (Table 6.1); why is iodised salt advisable; how does the body respond to adrenaline; why are diabetics given insulin injections.
Worked examples — real solved problems NCERT VERBATIM

Solved exactly as the source does them

Every problem is a real sourced item, quoted verbatim with its page; the step-by-step decoding and mark-logic are LazyTopper-authored coaching.

Example Fig. 6.2 reflex-arc walkthrough,
“[authored prompt] Trace, step by step, what happens in the reflex arc when you touch a hot object and pull your hand back.”
Receptor detects the stimulus.Heat and pain receptors in the skin of the hand detect the dangerous stimulus and generate a nerve impulse.
1 mark
Sensory neuron carries the input.The sensory neuron carries this impulse from the receptor towards the spinal cord.
1 mark
Relay in the spinal cord (the reflex arc).In the spinal cord the impulse is passed - through a relay neuron - straight from the incoming sensory nerve to the outgoing motor nerve, forming the reflex arc; the information also travels on to the brain.
1 mark
Motor neuron carries the output.The motor neuron carries the impulse from the spinal cord to the effector.
1 mark
Effector responds.The effector - the muscle in the arm - contracts and the hand is pulled back, all before the brain has consciously felt the pain.
1 mark
Mark-scheme logic (authored): CBSE 5-mark - 1 mark each for the receptor, the sensory neuron, the spinal-cord relay (the reflex arc), the motor neuron and the effector muscle response. The reflex arc is formed in the spinal cord so the response is quick; the signal still reaches the brain but the action does not wait for it.
Example Fig. 6.1 neuron walkthrough,
“[authored prompt] Explain how a nerve impulse is generated in a neuron and passed on to the next neuron across a synapse.”
Example Section 6.2 auxin walkthrough,
“[authored prompt] Explain, using the hormone auxin, how the shoot of a plant bends towards light coming from one side.”
Example Section 6.3 feedback walkthrough,
“[authored prompt] Describe how the level of sugar in the blood is controlled by insulin through a feedback mechanism.”
Problem-solving strategies AUTHORED
Diagram question?Draw it large and label with straight ruled lines, using the exact NCERT terms - cerebellum not balance centre, medulla not brain stem, axon not tail. The neuron, reflex arc, human brain and endocrine-gland diagrams are the ones most often asked.
Differences between asked?Answer in a two-column table - reflex action vs walking (voluntary), reflex vs involuntary action, nervous vs hormonal control, sensitive-plant movement vs growth movement. One crisp point per row scores faster than a paragraph.
Hormone question?Pair every hormone with its gland AND its function (Table 6.1): adrenaline-adrenal gland-fight or flight, thyroxin-thyroid-metabolism (needs iodine), insulin-pancreas-blood sugar, growth hormone-pituitary-growth. Examiners credit the gland and the function separately.
Why or how add-on?Board answers want the reason, not just the description - a reflex arc is quicker because the response is decided in the spinal cord, not the brain; iodised salt is advised because iodine is needed to make thyroxin. State the cause.
Common mistakes that cost marks

Where students lose easy marks

Writing that a reflex action is controlled by the brain - it is completed by the spinal-cord reflex arc; the impulse also reaches the brain, but the response does not wait for it.
Swapping the neuron parts: the dendrite RECEIVES information, the axon CARRIES the impulse away, and the gap between two neurons is the synapse (not the axon).
Mixing up cerebellum and medulla: the cerebellum controls posture, balance and precision of voluntary movement; the medulla controls involuntary actions such as blood pressure, salivation and vomiting.
Confusing plant hormones: auxin, gibberellin and cytokinin PROMOTE growth, while abscisic acid INHIBITS growth (it causes wilting). Naming abscisic acid as a growth promoter loses the mark.
Calling insulin or adrenaline a plant hormone - the plant hormones are auxin, gibberellin, cytokinin and abscisic acid; insulin, adrenaline, thyroxin and growth hormone are animal hormones.
Formulae
Neuron path
Dendrite (receives) to cell body to axon to nerve ending; the gap to the next cell is the synapse
Reflex arc
Receptor to sensory neuron to spinal cord (relay) to motor neuron to effector muscle
Brain regions
Fore-brain - thinking, senses, voluntary action, hunger; mid-brain and hind-brain - involuntary; cerebellum - posture and balance; medulla - blood pressure, salivation, vomiting
Plant tropisms
Phototropism (light), geotropism (gravity), hydrotropism (water), chemotropism (chemicals)
Plant hormones
Auxin - elongation and bending; gibberellin - stem growth; cytokinin - cell division; abscisic acid - inhibits growth (wilting)
Animal hormones (Table 6.1)
Growth hormone - pituitary; thyroxin - thyroid (needs iodine); insulin - pancreas (blood sugar); adrenaline - adrenal gland; testosterone - testes; oestrogen - ovaries
Mindmap
      • Receptors in the sense organs detect stimuli
      • Neuron - dendrite to cell body to axon; the synapse passes it on
      • Reflex action - reflex arc formed in the spinal cord (quick)
      • Brain - fore / mid / hind; cerebellum (balance), medulla (involuntary)
      • Protected by the skull, fluid and the vertebral column
      • Immediate movement - touch (sensitive plant folds by changing water content)
      • Growth movement - tropisms (slower)
      • Phototropism (light), geotropism (gravity), hydrotropism, chemotropism
      • No nerves or muscles - uses electrical-chemical and hormonal signals
      • Plant hormones - auxin, gibberellin, cytokinin, abscisic acid
      • Auxin makes the shoot bend towards light
      • Animal hormones - endocrine glands secrete into the blood
      • Adrenaline, thyroxin, insulin, growth hormone, sex hormones
      • A feedback mechanism keeps the amount right
      • A reflex action is completed by the spinal cord, not the brain
      • Dendrite receives, axon carries, the synapse is the gap
      • Cerebellum = balance; medulla = involuntary actions
      • Abscisic acid INHIBITS growth

The diagrams you must be able to draw and label - Control and Coordination is examined heavily through labelled figures. Learn each one in the exact NCERT form.

NCERT Fig 6.1(a)Structure of a neuron
The nerve cell - dendrites (receive information) around the cell body with its nucleus, the long axon that carries the impulse, ending in the nerve endings that pass it on.
NCERT Fig 6.2Reflex arc
The pathway of a reflex - heat/pain receptors in the skin, the sensory neuron to the spinal cord (CNS), the relay and motor neurons, and the effector muscle in the arm; the message also travels on to the brain.
NCERT Fig 6.3Human brain
Sectional view - fore-brain (cerebrum) inside the cranium, mid-brain, and the hind-brain parts (pons, medulla, cerebellum) leading to the spinal cord; the hypothalamus and pituitary gland are also labelled.
NCERT Fig 6.5Response of the plant to the direction of light
A germinated seedling in a flask inside a box open towards a window - the shoot bends towards the light while the roots grow away from it (phototropism).
NCERT Fig 6.6Plant showing geotropism
A potted plant laid on its side - the shoot turns upward, away from gravity (negatively geotropic) while the root turns downward, towards gravity (positively geotropic).
NCERT Fig 6.7Endocrine glands in human beings (a) male, (b) female
The endocrine glands and their positions - hypothalamus, pineal and pituitary glands, thyroid and parathyroid glands, thymus, pancreas, adrenal glands, and the testis (male) or ovaries and uterus (female).

3 competency questions from the CBSE board pattern, with the full step-marked solution for each — the marks are shown per step, as the official scheme awards them.

5 marksSection D

(a) How does blood sugar level get regulated in the human body? (b) (i) Which hormone is secreted into the blood when you are under stress? Name the gland that secretes this hormone. (ii) How does it help the body to cope up in an emergency situation?

Step-marked solution
  1. [1 mark] (a) Regulation of blood sugar: When the blood sugar level rises, the beta-cells of the pancreas detect it and secrete more of the hormone INSULIN.
  2. [1 mark] (a) Insulin lowers the blood sugar level by promoting the uptake of glucose and its conversion into glycogen; when the level falls, less insulin is secreted — this is controlled by a FEEDBACK MECHANISM.
  3. [1 mark] (b)(i) Under stress the hormone ADRENALINE is secreted into the blood; it is secreted by the ADRENAL GLAND, situated above the kidneys.
  4. [1 mark] (b)(ii) Adrenaline acts on the heart, making it beat faster so that more oxygenated blood is supplied to the skeletal muscles.
  5. [1 mark] (b)(ii) It also increases the breathing rate through contraction of the diaphragm and rib muscles and diverts blood to the muscles — preparing the body for a 'fight or flight' response.
3 marksSection C

A potted plant is kept near a window. After a few days its shoot is seen bending towards the light coming in through the window. Explain how the plant hormone controls this growth response of the shoot.

Step-marked solution
  1. [1 mark] The hormone auxin is synthesised at the shoot tip and diffuses down the shoot.
  2. [1 mark] When light falls from one side, auxin collects on the side of the shoot away from the light (the shaded side).
  3. [1 mark] Auxin causes the cells on the shaded side to elongate more, so that side grows faster and the shoot bends towards the light (phototropism).
1 markSection A

Sapna suffers from a condition due to which her average blood sugar level is 174 mg/dL. The average blood sugar level in a healthy adult is <140 mg/dL. Which of the following could be the cause of Sapna's condition?

  1. (A) insufficient production of thyroxine in her body
  2. (B) insufficient production of insulin in her body
  3. (C) excess production of thyroxine in her body
  4. (D) excess production of insulin in her body
Step-marked solution
  1. [1 mark] Correct option: (2) insufficient production of insulin in her body. Insulin lowers blood glucose; too little of it leaves the blood sugar persistently high, which is what her reading shows. Excess insulin would lower it, and thyroxine regulates metabolism rather than blood glucose directly.
Practise Control and Coordination competency questions

Official NCERT chapter PDF (jesc106) — ncert.nic.in

Sources: NCERT 2026-27 (tap to view)
Source ledger PROVENANCE

Source edition: NCERT Reprint 2026-27, Class 10 Science, Ch 6. One row per sourced item — every verbatim, example and NCERT figure traces to its page.

ItemTypeSource
ReceptorsverbatimNCERT 2026-27 Ch6
Nervous tissueverbatimNCERT 2026-27 Ch6
Reflex arcverbatimNCERT 2026-27 Ch6
Central nervous systemverbatimNCERT 2026-27 Ch6
CerebellumverbatimNCERT 2026-27 Ch6
PhototropismverbatimNCERT 2026-27 Ch6
AuxinverbatimNCERT 2026-27 Ch6
AdrenalineverbatimNCERT 2026-27 Ch6
SynapseverbatimNCERT 2026-27 Ch6
Peripheral nervous systemverbatimNCERT 2026-27 Ch6
MedullaverbatimNCERT 2026-27 Ch6
GeotropismverbatimNCERT 2026-27 Ch6
Abscisic acidverbatimNCERT 2026-27 Ch6
ThyroxinverbatimNCERT 2026-27 Ch6
InsulinverbatimNCERT 2026-27 Ch6
Feedback mechanismverbatimNCERT 2026-27 Ch6
Reflex action - withdrawing the hand from a hot objectexampleNCERT 2026-27 Ch6 Fig 6.2 -103
Transmission of a nerve impulse across a synapseexampleNCERT 2026-27 Ch6 Fig 6.1
How a shoot bends towards light (phototropism)exampleNCERT 2026-27 Ch6 Section 6.2
Hormonal control of blood sugar (feedback)exampleNCERT 2026-27 Ch6 Section 6.3 -111
NCERT Fig 6.1(a)figureNCERT 2026-27 Ch6 6.1(a)
NCERT Fig 6.2figureNCERT 2026-27 Ch6 6.2
NCERT Fig 6.3figureNCERT 2026-27 Ch6 6.3
NCERT Fig 6.5figureNCERT 2026-27 Ch6 6.5
NCERT Fig 6.6figureNCERT 2026-27 Ch6 6.6
NCERT Fig 6.7figureNCERT 2026-27 Ch6 6.7

Control and Coordination · spec-rendered note · NCERT Reprint 2026-27, Class 10 Science, Ch 6

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