What factors affect the rate of conduction of an action potential (AP) down a neurone?
- MYELINATION
A lipid myelin sheath is wrapped around the axon of the neurone in SEGMENTS. Only the parts of the axon exposed contain Na/K channels that will participate in the conduction of the AP. These segments are calls the NODES OF RANVIER. Since the propagation of the AP will involve local currents to be formed whereby the voltage-gated channels further down will be depolarised and hence open will result is the AP jumping from node to node. This is called SALTATORY CONDUCTION. Hence, myelination increases the rate of conduction. This helps understand how multiple sclerosis works since it leads to demyelination of the neurone hence slower conduction.
- AXON DIAMETER
The larger the axon the less resistance there is to the movement of ions within. Less resistance means ions can move more freely hence cause local potentials more easily. This is important when understanding why axons regrowing after injury are slower (since they have a reduced diameter)
- TEMPERATURE
Cooler temperatures decrease the rate of conduction. This is directly linked to factors affecting DIFFUSION. Higher temperatures allow ions to move at higher rates due to the amount of kinetic energy they possess.
Also DRUGS/COMPRESSION/ANOXIA (lack of oxygen)
