Nerve Impulses Flashcards
The resting potential
The inside of the neutron is more negative relative to the outside. The difference is maintained primarily by sodium-potassium pumps (Active membrane transport)
Action potentials
Are the rapid localised change in membrane charge that occurs in order to generate and propagate an electrical impulse along the neutron
Three main stages of action potentials
- Depolarisation
- Repolarisation
- Refractory period
How does depolarisation occur?
As a stimulus reaches the membrane, sodium channels allow Na+ to flow in, depolarising the membrane and making it less negative
What happens during the refractory period and why does refractory period occur?
At this stage, the resting ionic distribution is largely reversed. The resting potential must be restored by the sodium-potassium pump. The nerve can’t fire again until the resting potential is restored.
Repolarisation
The sodium channels then close and potassium channels open, allowing K+ ions to escape which causes the membrane potential to return to a more negative internal differential
Propagation of the action potential
- Nerve impulses are action potentials that move along the length of an axon as a wave of depolarisation
- The ion channels that occupy the length of the axon are voltage-gated
- Depolarisation at one point of the axon triggers the opening of the ion channels in the next segment of the axon
Oscilloscopes
Oscilloscopes measure and show the membrane potential changes at rest and during an action potential.
Myelin
Some neutrons are covered in a fatty, white, insulating substance called myelin. This layer increases the speed of nerve impulse in transmission by saltatory conduction
Myelination
In myelinated neurons, the action potentials’ a hop between the gaps in the myelin sheath called the nodes of ranvier
