Coordination and Response IGCSE Biology: Complete Guide

🧠 Understanding Coordination and Response in IGCSE Biology

Coordination and response systems help organisms react to environmental changes. This guide covers nervous system, hormones, and reflexes.

🧠 Memory Tips

Nervous System: “Central Peripheral”

• CNS: Brain and spinal cord
• PNS: All other nerves

Reflex Arc: “Stimulus Receptor Sensory Relay Motor Effector Response”

• Stimulus → Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector → Response

Hormones vs Nerves: “Hormones Slow Chemical, Nerves Fast Electrical”

📚 Key Concepts

Nervous System

• Function: Rapid communication
• Neurons: Nerve cells
• Impulses: Electrical signals
• Synapses: Gaps between neurons

Reflex Actions

• Automatic responses: No conscious thought
• Protective: Prevent injury
• Fast: Bypass brain
• Examples: Knee jerk, blinking, withdrawal

Endocrine System

• Hormones: Chemical messengers
• Glands: Produce hormones
• Target organs: Respond to hormones
• Slower: Than nervous system

Key Hormones

• Insulin: Controls blood glucose
• Adrenaline: Fight or flight response
• Growth hormone: Controls growth
• Thyroxine: Controls metabolism

Homeostasis

• Definition: Maintaining constant internal environment
• Examples: Temperature, blood glucose, water balance
• Negative feedback: Corrects deviations

🎯 Exam Focus

Common Questions:

1. Draw and label reflex arc (5 marks)
2. Compare nervous and endocrine systems (6 marks)
3. Explain homeostasis mechanisms (4 marks)

Key Processes:

• Stimulus → Response pathway
• Hormone regulation mechanisms
• Negative feedback loops

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