Control and Coordination · Class 10 Science: quick revision, 45 bites

Animals Need Speed

Why deer beat daffodils at dodging

Coordination in animals is built around **speed** — sensing danger and food, and acting in milliseconds. The specialised cell that makes it possible is the **NEURON**, a living electrical wire.

Takeaway. Fast responses demand a wired network — the nervous system.

The Neuron's Parts

A cell stretched into a wire

Takeaway. Receive, process, conduct, pass on.

The Synapse

The gap the spark can't jump

Between neurons lies a microscopic gap — the **synapse**. The arriving electrical impulse releases **chemicals**; they drift across and restart the impulse in the next neuron's dendrites. The same chemistry commands muscles and glands.

Takeaway. Electrical along the wire, chemical at the junction.

Receptors

The body's sensor catalogue

Takeaway. Five families of detectors feed the network.

Reflex Action

Gone before the ouch

Touch a flame — the hand withdraws **before pain registers**. A reflex is a rapid, automatic response that skips the brain's deliberation entirely. The thinking is outsourced to the spinal cord.

Takeaway. Reflex = instant response, zero thinking.

The Reflex Arc

Five stations, no pauseing

Takeaway. Receptor → sensory → spinal cord → motor → effector.

Why Reflex Arcs Exist

Why evolution kept the shortcut

The brain's rich processing takes TIME an emergency doesn't grant. The spinal shortcut answers in milliseconds; the brain merely receives the report afterwards (the pain you feel). Efficient enough that evolution kept reflex arcs even after big brains arrived.

Takeaway. Speed first, awareness second.

Fore-Brain (Cerebrum)

The thinking floor

Takeaway. The cerebrum is where 'you' happens.

Cerebellum

The balance engineer

Orders come from the cerebrum, but the **cerebellum** (hind-brain) makes them GRACEFUL: precision of voluntary actions, posture, balance. Cycling through traffic, walking a straight line, lifting a pencil in one clean arc — all cerebellum polish.

Takeaway. Cerebrum commands; cerebellum choreographs.

Medulla and Mid-Brain

The autopilot deck

**Medulla** (hind-brain): blood pressure, salivation, vomiting — involuntary life-support you never think about. **Mid-brain**: involuntary adjustments like **pupil size** changing with light. **Pons** joins in regulating breathing.

Takeaway. The body's autopilot lives below the thinking floor.

Protecting Brain and Cord

Armour and airbags

The brain floats in a **fluid-filled cushion** inside the bony **skull** — the liquid absorbs shocks like a built-in airbag. The spinal cord threads through the **vertebral column**'s protective rings. Helmets are humanity's add-on to the same design.

Takeaway. Fluid cushion + bone case = factory-fitted protection.

Muscles Obey by Folding Proteins

How thought becomes motion

The chain ends at a muscle cell: the nerve's chemical lands, and **special muscle proteins change shape and arrangement**, shortening the cell. Millions shortening together = contraction = movement. Decision becomes deed through protein origami.

Takeaway. Nerve chemical in → proteins refold → cell shortens → limb moves.

The Knee-Jerk Test

The doctor's rubber hammer

Takeaway. One tap audits the entire emergency circuit.

Board Favourites

The bankers of this topic

Takeaway. Five staples carry the marks here.

Memory Pack

Whole topic in three lines

Takeaway. Three codes, the whole wiring diagram.

Two Kinds of Plant Movement

No nerves, no muscles — still moving

Takeaway. Fast water tricks vs slow growth steering.

Touch-Me-Not's Turgor Trick

The plant that flinches

Touch Mimosa pudica and hinge cells at the leaflet bases **dump their water** — turgor collapses, cells go limp, leaflets fold shut. Signal relayed cell-to-cell, movement made hydraulically. **No growth, no muscle — just water pressure released.**

Takeaway. The fold is plumbing, not flexing.

What Is a Tropism?

Growth with a compass

Takeaway. Direction-locked growth = tropism.

Phototropism

Shoots chase light, roots flee it

Shoots bend **toward** one-sided light (positive phototropism); roots bend **away** (negative). Keep a potted plant by a window and its new growth writes the proof in its curve.

Takeaway. Shoot +, root − for light.

Geotropism

Gravity's opposite readings

Roots grow **with** gravity (positive geotropism), shoots **against** it (negative). Lay a seedling on its side: within days the root elbow-bends downward and the shoot upward — each organ re-reading the same pull oppositely.

Takeaway. Root down, shoot up — always.

Hydrotropism and Chemotropism

Water-seekers and chemical-followers

Takeaway. Roots follow water; pollen tubes follow chemistry.

Thigmotropism — Tendrils

The climbing handshake

A tendril touching a support grows **slower on the touching side** and faster on the free side — the imbalance coils it around the prop. Slow-motion gripping by pure growth arithmetic.

Takeaway. Unequal growth = the tendril's curl.

Auxin and the Bend

The hormone that steers with shade

Takeaway. Shade Side Stretches — that's phototropism.

Auxin, Gibberellin, Cytokinin

The growth accelerators

Takeaway. Elongate, heighten, divide — the three pushers.

Abscisic Acid and Ethylene

The brake and the ripener

Takeaway. ABA stops the party; ethylene sweetens it.

How Plant Hormones Travel

Post, not telegraph

Made in one tissue, acting in another, plant hormones move by **diffusion** (and in the sap streams). Slow compared to nerve impulses — but a rooted organism has nowhere to run and no need to hurry.

Takeaway. Chemical post suits the stationary life.

Touch-Me-Not vs Tendril

Same stimulus, two mechanisms

Takeaway. Both answer touch — by opposite machinery. Exam favourite!

Ethylene in Commerce

The fruit-seller's secret

Takeaway. Ripening on demand = hormone chemistry, industrialised.

Board Favourites

The bankers of this topic

Takeaway. Five staples rule this topic's papers.

Memory Pack

Whole topic in three lines

Takeaway. Three codes, the whole green control room.

What Hormones Are

The bloodstream broadcast

Slower than nerve impulses — but body-wide and sustained.

Takeaway. Chemicals in blood = the body's radio broadcast.

Ductless Glands

No pipes attached

Takeaway. Endocrine = straight into the bloodstream.

Adrenaline — Fight or Flight

The 10-second body takeover

Takeaway. One hormone, every organ, instant emergency mode.

Nerves + Adrenaline Teamwork

Wire triggers broadcast

The brain PERCEIVES the danger (nervous, milliseconds) and nerve signals order the adrenal glands to secrete (hormonal, seconds, body-wide). The two systems aren't rivals — the fast one pulls the slow one's trigger.

Takeaway. Nervous perception fires the hormonal cannon.

Thyroxine and Metabolism

The neck's fuel regulator

The **thyroid** secretes **thyroxine**, which sets the body's processing rate for **carbohydrates, proteins and fats** — the metabolic thermostat sitting in your neck.

Takeaway. Thyroxine = the metabolism manager.

Iodine and Goitre

Why your salt packet says 'iodised'

Takeaway. No iodine → no thyroxine → goitre. Salt solves it.

Growth Hormone

Feet and inches from a pea

The pea-sized **pituitary** secretes **growth hormone**, governing growth and development. Childhood deficiency → **dwarfism**; childhood excess → **gigantism**. The master gland's most visible verdict.

Takeaway. Pituitary GH writes your height.

Insulin and Diabetes

The sugar gatekeeper

The **pancreas** secretes **INSULIN**, which lowers and regulates blood sugar. Insufficient insulin → sugar stays high in blood (spilling into urine) → **DIABETES**, with its many harms. Management: insulin injections supplying what the pancreas cannot.

Takeaway. Insulin down → sugar up → diabetes.

Testosterone and Oestrogen

Adolescence's chemists

Puberty's transformation is hormonal: **testosterone** (from the testes) drives male changes; **oestrogen** (from the ovaries) drives female changes — growth spurts, voice, and the secondary sexual characteristics.

Takeaway. Two hormones re-engineer the teenage body.

Feedback — Insulin's Loop

The tap that turns itself

Takeaway. The response regulates its own trigger — a living thermostat.

Glands and Hormones at a Glance

The full roster

Takeaway. Six glands, six hormones — the exam's favourite table.

Nervous vs Hormonal Control

Telephone vs radio

Takeaway. Fast-narrow-brief vs slow-wide-lasting — the body keeps both.

Adrenaline You Have Felt

The pre-exam pounding heart

Takeaway. Exam nerves are a chemistry lesson running live.

Board Favourites

The bankers of this topic

Takeaway. Five staples own this topic's mark-sheet.

Memory Pack

Whole topic in three lines

Takeaway. Three codes, the whole chemical government.