INTRO: Is That Thing Alive?
Let’s start with a riddle:
If it grows, it lives. If it moves, it lives. But not all movement means growth. Then what does it mean?
A plant seedling pushing soil, a cat chasing a mouse, or you running from your math teacher—what’s common? Movement.
But here’s the catch: not all movement is caused by growth. When you run from danger or reach for candy, you’re responding to something. These responses to stimuli are not random but coordinated. And coordination needs—drumroll please—Control Systems!
So let’s dive into how animals and plants do this magical coordination show.
6.1 ANIMALS – NERVOUS SYSTEM
Keywords: Neuron, Impulse, Synapse, Receptor, Muscles, Neurotransmitter
Imagine a courier service. Receptors receive a parcel (stimulus), pass it to a neuron (delivery guy), and it zooms across a highway (axon), makes a delivery (synapse), and the message is received by muscle cells—who act like workers that now move!
Let’s understand this with an actual Neuron diagram:
🧠See Image 1:
- Information is received by dendrites
- Travels as an electrical impulse through the axon
- Reaches the nerve ending, where it triggers chemicals (neurotransmitters) across a synapse
Receptors in your skin detect a hot object. This message zips through neurons and makes your muscle jump back. Voilà —coordinated protection!
But wait… what if there’s no time to think?
6.1.1 Reflex Action – Fast & Furious
When you touch a hot cup, do you pause and say, “Hmm, should I move my hand?” NO! You jump back faster than a cricket ball being caught.
Why? Because of a pre-installed shortcut: Reflex Arc.
🧠See Image 3:
- Sensory neurons send the message to the spinal cord
- Instead of going all the way to the brain, relay neurons directly pass it to motor neurons
- The effector (muscle) moves instantly!
It’s like a fire drill in a school—no debates, just action!
👉 So now, a question: If reflex actions are fast but limited, who’s doing the real thinking?
6.1.2 Human Brain – The Thinking Boss
Enter the Brain—the CEO of your body.
🧠See Image 4:
- Forebrain: The office for thinking, memory, logic. It tells your hand to write and your eyes to roll.
- Midbrain: A quick messenger for sensory signals.
- Hindbrain:
- Medulla: Manages breathing, heart rate, and vomiting (yep, not your willpower).
- Cerebellum: Keeps your walk balanced. Imagine it as the dance choreographer.
Your brain is packed in a bony skull and cushioned in fluid. Like a phone in a shockproof case—because it’s precious.
🧠Bonus: Your spinal cord is also well-protected inside your vertebral column.
👉 Now that the nervous system is so advanced, why do we still use slow methods like hormones?
6.2 Coordination in Plants – The Slow & Steady
Wait—plants don’t have brains or muscles. But touch a chhui-mui, and it folds up like it’s shy!
🪴 See Image of Mimosa Plant
This is nastic movement—fast but not due to growth. Water moves in and out of cells, making them change shape. Voilà —movement!
Now let’s talk tropic movements: directional growth triggered by light, gravity, etc.
🪴 See Image of plant with directional growth
- Phototropism: Shoots bend towards light
- Geotropism: Roots grow downward
- Hydrotropism: Roots grow towards water
- Chemotropism: Pollen tubes grow towards ovules (love guided by smell?).
And who runs this slow but majestic show? Plant Hormones:
- Auxin: Helps cells grow longer
- Gibberellin: Makes stems grow tall
- Cytokinin: Promotes cell division
- Abscisic Acid: Brakes the growth (plant version of “Nope, not now!”)
👉 So if plants can do all this without nerves, what happens when animals need slow but wide-spread responses?
6.3 Hormones in Animals – Chemical Messages That Talk
Imagine a squirrel sees a snake. What happens?
Adrenaline yells “RUN!” and the body:
- Pumps heart faster
- Diverts blood to muscles
- Speeds up breathing
🎯 This is the work of endocrine glands, your body’s chemical post office.
🧬 See Image 5:
- Adrenal gland: Adrenaline
- Pituitary gland: The master gland
- Thyroid gland: Needs iodine for thyroxin to regulate metabolism
- Pancreas: Produces insulin—controls blood sugar
- Testes/Ovaries: Produce testosterone/oestrogen—control puberty
- Hypothalamus: Sends instructions to pituitary—like a whispering boss.
🎯 All hormones work on feedback loops.
Example: Too much sugar? Insulin kicks in. Too little? Insulin relaxes.
👉 Now tell me—what if we had no coordination between these hormones? (Chaos, like 10 drummers drumming out of sync.)
Summary – The Symphony of Life
Every action, from blinking to solving algebra, involves a symphony of:
- Electrical impulses in neurons
- Chemical messengers in synapses
- Muscle contraction by protein reshuffling
- Hormonal signals for long-term effects
Whether it’s a child running, a plant bending, or a brain thinking—it’s all about control and coordination. Without it, life would be like a phone without a processor. It might look smart, but it won’t respond to a thing.