Myleinated axons

how does the action potential jump from node to node in a myelinated axon?

Na+ ions will diffuse directly from one node to another, from an area of high concentration to an area of low. This increases the potential difference above the threshold value, which will generate another action potential at the next node. This will keep happening from node to node. It is called Saltatory Conduction (latin for jumping).

Reply 2

username459260

OP

16

Original post by BigWilfo

Na+ ions will diffuse directly from one node to another, from an area of high concentration to an area of low. This increases the potential difference above the threshold value, which will generate another action potential at the next node. This will keep happening from node to node. It is called Saltatory Conduction (latin for jumping).

but why is there nothing between the nodes?

Reply 3

NutterFrutter

Original post by jsmith6131

but why is there nothing between the nodes?

Khanacademy has videos on this.

Reply 4

Supermassive_muse_fan

10

Original post by jsmith6131

but why is there nothing between the nodes?

For faster conduction of an action potential. The actional potential doesn't move in a wave-like manner across the neuron but rather jumping from node to node as said above.

Reply 5

BigWilfo

Original post by jsmith6131

but why is there nothing between the nodes?

The myelinated sheath is impermeable to any ions, so there is no ion channels on the parts of the axon membrane surrounded by the myelinated sheath. This means the DISTANCE from the permeable voltage gated Na+ channels is further away, so the Na+ ions can just diffuse from one to the other, making it much faster. As there are only ion channels on the nodes of ranvier, the Na+ just "jump" from one to the other.

Reply 6

username459260

OP

16

but why would diffusion be faster in a myelinated axon than an un-myenlinated?

Reply 7

Nepene

10

Original post by jsmith6131

but why would diffusion be faster in a myelinated axon than an un-myenlinated?

Saltatory conduction. The myelination ensures that ions don't leak, so the magnetic field of the ions is enough to depolarize the next node very fast, and so on and so forth. The action potential then propagates fast.

Myleinated axons

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