Explain what an action potential is, and describe how it moves down the axon and across the synapse?
The action potential (electrical impulse) is pulled along the cell by positive ions entering and attracting it before leaving again.
An action potential is the electrical signal that travels down the neuron cell.
The electrical signal is negatively charged, because it is, obviously, electrical. It is drawn along the neuron by a series of positive ions appearing in front of it and pulling it forward. Imagine if you tied a string to a ten pound note and pulled it along the street with a cartoon character chasing after it - that's how I like to think of it.
The inside of the neuron cell is normally negatively charged relative to the outside. Ion channels open when the electrical signal enters the cell and pump
Since the cell is normally negative, or polar, the influx of positive ions is known as a depolarisation, because it turns the cell more positive in that area. However, once the cell has reached a certain level of depolarisation, the
While this is happening, some of the
The series of depolarisation and repolarisation along the cell makes the action potential move down the axon.
When an electrical impulse reaches the synapse, it opens calcium channels. The calcium enters and causes vesicles (bubbles) of neurotransmitters to bind to the membrane and release the chemicals. The neurotransmitter molecules drift across the synapse and bond to receptors on the next neuron, which initiates the electrical signal and the process of de- and repolarisations repeats.