PSYC 211 Chapter Notes - Chapter 2.5: Dendritic Spine, Saltatory Conduction, Axoplasm
3 Jun 2016
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The all or none law is the basic law of axonal conduction. This law states that an action potential either occurs or does not occur and, once triggered, it is transmitted down the axon to its end. The strength of a stimulus can vary from barely detectable to very intense. Conduction of an action potential in a myelinated axon is somewhat different from conduction in an unmyelinated axon. The only place where an unmyelinated axon comes into contract with the extracellular fluid is at the node of ranvier. In the myelinated areas there can be no inward flow of na+ when the sodium channels open because there is no extracellular sodium. Saltatory conduction offers two advantages to do with economy and speed. Sodium ions enter axons during action potentials, and these ions must eventually be removed: on unmyelinated axons, there must be sodium-potassium pumps across their length as.
