1.4 - D - Transport in Axons
Neurons are specialized cells that make up the nervous system. They are specialized to carry electric signals down long stretches called axons. Signals are transmitted down the axon in the form of an action potential, which is a different in ion concentration inside and outside of the cell. To pass this action potential down the axon, various protein channels and pumps are used.
Two discussed here are:
The basic function of these protein channels is described below and will be covered in more detail in Topic 6.3.
After an action potential has passed on area, sodium-potassium pumps are used to restore the local action potential. To do this, ATP is used to pump 3 Na+ ions out and 2 K+ ions in. This imbalance in charge brings the potential down to a negative value where it reminds until the next action potential propagates through the area.
When the potential in the the axon becomes too positive, voltage-gated potassium channels open. These allow the potassium inside the axon to diffuse outwards, which helps restore the potential to the initial value.
The structure of the potassium channel: