35. ACTION POTENTIAL MOVEMENT IN A NERVE AXON

[Editor]

A) requires calcium conductance
B ) is slowed by the presence of a myelin sheath
c) requires activation of voltage gated sodium channels
d) requires the Na/K ATPase pump
e) can occur up to 120 meters/sec in C fibres

[Editor]

FFTTF

Nerve conduction of an action potential is an all or none phenomenon. It is a wave of propergated depolarization by opening of voltage gated sodium channels. These open once the resting threshold of -55mv is reached.
Calcium ions are required for presynaptic acetylcholine vesicle release and for second messenger systems. This may be via electro-mechanical coupling or via activation of protein phospohorylation of via the PIP2 second messenger system.
In order for the resting membrane to be kept below the threshold potential the NA/K ATPase pump is required. The speed of conduction may be as fast as 120 meters/second in motor neurones. In the slower C fibres this occurs between 05-2 meters/second.