Explain what happens when an impulse arrvies at a junction between two neurones

At each junction there is a neurone that comes before it called the presynaptic neurone and one that comes after called the post synaptic neurone and the space between the two neurones is called the synapse. An impulse otherwise known as an action potential arrives at the pre synaptic neurone, the arrival of this action potential causes calcium channels to open and calcium floods into the cell. Although inside the neurone is positive and calcium is positively charged this can happen because calcium is pumped in using energy / ATP pump. This calcium is important because is causes chemicals called neurotransmitters to be released from the presynaptic neurones into the synapse. Here they move towards and attach to receptors on the post synaptic neurone. This attaching to the receptors causes a new action potential to be generated in the next neurone and the process can continue.