Nerve impulses?

Question

Why do nerve impulses move faster along myelinated nerve fibres?

Answer 1

Neurones send messages electrochemically; this means that chemicals (ions) cause an electrical impulse. Neurones and muscle cells are electrically excitable cells, which means that they can transmit electrical nerve impulses. These impulses are due to events in the cell membrane, so to understand the nerve impulse we need to revise some properties of cell membranes
When a neurone is not sending a signal, it is at ‘rest’. The membrane is responsible for the different events that occur in a neurone. All animal cell membranes contain a protein pump called the sodium-potassium pump (Na+K+ATPase). This uses the energy from ATP splitting to simultaneously pump 3 sodium ions out of the cell and 2 potassium ions in.

If the pump was to continue unchecked there would be no sodium or potassium ions left to pump, but there are also sodium and potassium ion channels in the membrane. These channels are normally closed, but even when closed, they “leak”, allowing sodium ions to leak in and potassium ions to leak out, down their respective concentration gradients
The combination of the Na+K+ATPase pump and the leak channels cause a stable imbalance of Na+ and K+ ions across the membrane. This imbalance of ions causes a potential difference (or voltage) between the inside of the neurone and its surroundings, called the resting membrane potential. The membrane potential is always negative inside the cell, and varies in size from –20 to –200 mV (milivolt) in different cells and species (in humans it is –70mV). The Na+K+ATPase is thought to have evolved as an osmoregulator to keep the internal water potential high and so stop water entering animal cells and bursting them. Plant cells don’t need this as they have strong cells walls to prevent bursting.

Answer 2

It's like any electric wire. If an electric wire is not insulated (has no covering) all other sorts of foreign matter may land on it. Dirt? Etc. Or metal which affects the transmission of the electrical signal.

So the myelin sheath acts as an insulation. Or else the electric impulse would be lost to areas outside the nerve.

Answer 3

It insulates and moves the impulses along not in a wave, but in " saltations " of energy,. Does a couple of other things, things to do with resistance. A t wkipedia, under " myelin sheath ".

Answer 4

my nerve impulse and car travels at the speed of light! chiuuu!

Answer 5

because the myelin sheath is an insulator,so the nerve impulse speed in the thick fibers is 140m/s while in thin myelinated is12m/s

Answer 6

because the signal can jump between the nodes that separate the myelin bundles rather than traveling the full distance along the neuron