Cells & Systems

🌟 Big Idea

Your body is like a team of systems that all work together to keep you alive and healthy.
No system works alone—they’re constantly helping each other out!

🍔Digestive System (How food becomes fuel)

Think of this as your body’s food processing factory.

🚶‍♂ The journey of food:

  1. Mouth 👄

    • Chewing = mechanical digestion (breaking food into pieces)

    • Saliva = starts chemical digestion (enzymes break down starch)

  2. Esophagus

    • Food slides down using peristalsis (muscle waves)

  3. Stomach 🥣

    • Churns food + strong acids break it down

    • Mucus protects the stomach from digesting itself

  4. Small Intestine 🧬

    • Nutrients are absorbed into the blood

    • Tiny structures (villi + microvilli) = more surface area = better absorption

  5. Large Intestine 🚽

    • Water removed

    • Waste becomes feces and exits the body

🌬 Respiratory System (Breathing = gas exchange)

Your body’s air system.

  • You inhale oxygen (O₂) and exhale carbon dioxide (CO₂)

  • The diaphragm helps you breathe in and out

Inside your lungs:

  • Tiny air sacs called alveoli

  • Oxygen moves into blood, carbon dioxide moves out
    👉 This happens by diffusion

❤ Circulatory System (Transportation system)

Your body’s delivery network 🚚

Main parts:

  • Heart ❤ = pump

  • Arteries = carry blood AWAY from heart

  • Veins = bring blood BACK to heart

  • Capillaries = tiny vessels where обмен (exchange) happens

🩸 Blood = what’s inside the system:

  • Plasma (55%) = carries stuff

  • Red blood cells (44%) = carry oxygen

  • White blood cells (<1%) = fight disease 🦠

  • Platelets (<1%) = help blood clot 🩹

👉 This system works closely with:

  • Digestive system (nutrients)

  • Respiratory system (oxygen)

🚽 Excretory System (Waste removal)

Your body’s cleanup crew 🧹

What happens:

  • Waste like ammonia is made by cells

  • Liver turns it into urea (less harmful)

  • Kidneys filter blood → make urine

Path of urine:

Kidneys → Ureters → Bladder → Urethra

Bonus:

  • Sweating removes salt + cools you down 🥵

🧠 Nervous System (Control center)

Your body’s communication system ⚡

Main job:

Send and receive messages FAST

🧬 Neurons:

  • Dendrites = receive messages

  • Axon = sends messages

  • Synapse = gap between neurons

Two main parts:

  1. Central Nervous System (CNS)

    • Brain 🧠 + spinal cord

  2. Peripheral Nervous System (PNS)

    • Nerves all over body

Types of responses:

  • Automatic (heartbeat, sweating)

  • Voluntary (moving your arm)

🔥 Reflexes & Temperature Control

Your body reacts quickly without thinking:

  • Touch something hot → pull away 🔥

  • Cold → shiver (makes heat)

  • Hot → sweat (cools you down)

The hypothalamus in your brain keeps your body temperature stable.

🧪 Section 4 – Science & Health

🦠Discoveries That Changed Medicine

  • Edward Jenner → created first vaccine (smallpox)

  • Louis Pasteur → proved germs cause disease

  • Joseph Lister → introduced clean surgery

  • James Lind → discovered Vitamin C prevents scurvy

⚠ What Affects Your Body Systems?

Things that can harm your body:

  • Smoking 🚬

  • Poor diet 🍟

  • Lack of exercise 🛋

  • Stress 😰

  • Pollution 🌫

  • Disease or genetics

🚬 Smoking (Major danger)

Cigarettes contain harmful chemicals:

  • Tar = damages lungs

  • Carbon monoxide = reduces oxygen in blood

  • Nicotine = addictive + raises heart rate

Can lead to:

  • Bronchitis

  • Emphysema

  • Lung cancer

❤ Circulatory Problems

  • High blood pressure (hypertension)

  • Heart attacks

  • Stroke

Causes:

  • Smoking

  • High-fat diet (cholesterol buildup)

  • Lack of exercise

🍽 Digestive Health

Your body needs:

  • Carbs = energy ⚡

  • Fats = energy + protection

  • Proteins = growth + repair 💪

  • Vitamins + minerals = overall health

Problems:

  • Ulcers (caused by bacteria)

  • Low fiber → colon issues

✅ Healthy Lifestyle = Strong Body

To keep all systems working well:

  • Eat healthy 🥗

  • Exercise regularly 🏃‍♂

  • Sleep enough 😴

  • Avoid harmful habits 🚫

👉 When you take care of your body, your immune system stays strong and fights disease better