The Synapse (Cambridge (CIE) IGCSE Biology): Revision Note

The junction between two neurones is known as a synapse

Neurones are not directly connected to one another

The junctions (gaps) in between them are called synapses

Several events occur at a synapse to transmit an impulse from one neurone to the next:

• an impulse arrives at the end of an axon

• the impulse triggers the release of neurotransmitters from vesicles into the synaptic gap

• the neurotransmitter molecules diffuse across the synaptic gap

• the neurotransmitter molecules then bind with receptor proteins on the membrane of the next neurone

• an impulse is then stimulated in the next neurone

Synapses ensure that impulses only travel in one direction, avoiding confusion within the nervous system if impulses were travelling in both directions

Since this is the point in the nervous system where messages are transmitted chemically rather than electrically, synapses are a common target for drugs affecting the nervous system; for example, this is how heroin works