Edexcel A Level (IAL) Biology -8.5 Myelination & Saltatory Conduction- Study Notes- New Syllabus

Role of Myelination in Saltatory Conduction

🌱 Introduction

Myelin is a fatty sheath produced by Schwann cells around axons in the PNS (or oligodendrocytes in CNS).
It insulates the axon and allows impulses to travel faster and more efficiently.

🔍 Key Features

1. Structure

• Axon is wrapped in layers of myelin.
• Nodes of Ranvier: small gaps between myelin segments.
• Axon membrane exposed only at nodes.

2. How Saltatory Conduction Works

• Action potential occurs only at the nodes.
• Depolarisation jumps from one node to the next instead of moving continuously.
• Reduces the number of times ions cross the membrane → faster impulse.

3. Advantages of Myelination

• Speeds up conduction: impulses travel much faster than in unmyelinated axons.
• Energy efficient: fewer ions moved → less ATP used by sodium-potassium pumps.
• Prevents signal loss: insulation keeps the impulse strong over long distances.

📌 Summary Table