BIOB34H3 Chapter Notes -Hyperkalemia, Multiple Sclerosis, Demyelinating Disease
Document Summary
Conduction the high speed movement of an action potential along the axon. During an action potential, lost energy is constantly replenished. Axon contains many voltage-gated na+ channels: when depolarization reaches these, the open and allow more na+ to enter reinforcing the depolarization, this mechanism initiates the positive feedback loop. It is repelled by na+ that entered the cytoplasm and attracted by the negative charge of the resting membrane potential. The continuous entry of na+ ensures the signal wont diminish as the action potential propagates itself. That section of axon is in the absolute refractory period so has inactivated na+ channels. Some organisms use giant axons for rapid escape responses (e. g. squid, earthworms, fish: up to 1mm in diameter, these have been important in electrical signaling research because they are easily punctured with electrodes. Complex nervous systems pack more axons into a nerve using smaller- diameter axons: these are wrapped in myelin (insulating membranes) to improve speed.
