BIO 208 Lecture Notes - Lecture 12: Myelin, Excitatory Synapse, Membrane Potential
19 Sep 2016
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Recording at a single position along an axon in response to 4 diff depolarizing stimuli: axon responds in all or none fashion when depolarization exceeds threshold: membrane is normally inside negative at -70 mv. We call this response all-or-none: the depolarization involves an increase in permeability of the membrane to sodium (na). Space constant: an axon is not a wire with low resistance. Rather it is a membrane with a fluid filled interior. If an electrical signal is introduced into an axon, it will be observed at most 2-3 mm away due to decay of the potential (unlike a wire which is passive). Long axon (up to 2 meters) must overcome this problem. Axon does this by developing a repeater mechanism. The action potential at one site sets up a depolarization at a neighboring inactive site that initiates an action potential. This is how the signal travels along the axon: ap ap ap and so on.
