BIOL 3P34 Lecture Notes - Lecture 12: Squid Giant Axon, Saltatory Conduction, Schwann Cell

• School: Brock University
• Department: Biological Sciences
• Course: BIOL 3P34
• Professor: S

Document Summary

Increasing diameter of axonal core: saltatory conduction: myelination of axons. Nodes of ranvier - interruptions in the myelin sheath. Depends on diameter of axon ( diam : speed) Aps develop only at nodes of ranvier (myelin restricts current flow). Myelinated axons also capable of firing faster and longer. Velocities vary from a few m/s to 100 m /s. World speed record : myelinated axons of shrimp: >200 m/s (447 miles / hr) Characterized by areas of demyelination of brain and spinal cord axons. Results of demyelination: dramatic effects on nerve fibres. Saltatory conduction more energy efficient than conduction along entire length of axon. Loss of myelin causes one or more of: Blood-brain barrier is disrupted at onset of symptoms. Acute inflammatory response of lymphocytes and macrophages produce demyelination by direct or indirect mechanisms. The dysregulated immune system no longer prevents memory t-cells from acting against myelin, entering cns and mediating damage.