Chapter 19: Chemical Coordination and Integration

🤝 Why We Need Chemical Coordination

Our body has two teamwork systems:

  • ⚡ Neural system: Super-fast messaging (like texting!), but effects are short-lived. Nerve fibers can’t reach every cell.
  • 🐢 Endocrine system: Slower but long-lasting coordination using hormones. It fills in where nerves can’t reach!

Together, they regulate body functions like a perfect duo! 🦸‍♂️🦸‍♀️

🧪 What Are Endocrine Glands?

  • ❌ NO ducts (tubes to carry secretions). That’s why we call them “ductless glands”!
  • 💧 Their secretions are called hormones.

🔬 What Exactly Are Hormones?

Classic definition: Chemicals made by endocrine glands that:

  1. Enter the bloodstream 🩸
  2. Travel to distant organs 🚛
  3. Act on target organs 🎯

Modern definition: Hormones are…

  • 🧪 Non-nutrient chemicals (not food!)
  • 📨 Intercellular messengers (cell-to-cell mail!)
  • 💡 Made in tiny trace amounts

✨ Fun fact: This new definition includes more molecules than just those from classic glands!

🐛🦒 Hormone Systems in Animals

  • Invertebrates (like worms/insects): Simple systems, few hormones. 🐌
  • Vertebrates (like humans/animals): Complex systems, LOTS of hormones. 🐯

🎯 NEET Must-Knows

  • ⭐ Hormones vs. Nerves: Nerves = fast/short-term ⚡, Hormones = slower/long-term 🐢 + reach more cells.
  • ⭐ Ductless = Endocrine: No tubes! Hormones go straight into blood. 🚫🧪
  • ⭐ Hormone Definition: Non-nutrient chemicals 🚫🍔, messengers ✉️, made in traces 🔍.
  • ⭐ New vs. Old Definition: Modern definition includes MORE messenger molecules 💌.