BRAINCAKESaltatory Conduction
In a myelinated neurone, the myelin sheath insulates the axon membrane so ions cannot move across it, except at the nodes of Ranvier. Depolarisation can therefore only happen at the nodes.
When an action potential occurs at one node, the Na+ entering the axon sets up local currents that flow inside the axon, under the myelin, to the next node. These currents depolarise the membrane at the next node to threshold, and an action potential is generated there. The impulse appears to jump from node to node. This is saltatory conduction, from the Latin saltare, to jump.
Saltatory conduction has two advantages over conduction along an unmyelinated axon:
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Key terms in this lesson
- local currents
- The sideways movement of ions inside and outside an axon that spreads depolarisation to the next region of membrane.
- nodes of ranvier
- Small gaps between adjacent Schwann cells where the axon membrane is exposed and ion channels are concentrated.
- myelin sheath
- An insulating layer of Schwann cell membrane wrapped around an axon that speeds up nerve impulse conduction.
More in Mammalian Nervous System
- Repolarisation
- Hyperpolarisation
- Refractory Period
- Transmission of Nerve Impulses
- Synapses
- Pre-synaptic Membrane
- Post-Synaptic Membrane
- Neurotransmitters
All 38 lessons in Mammalian Nervous System · All Edexcel A-level Biology topics