1. Biopsychology 2
AQA A Specification:The structure and function of sensory, relay and motor neurons. The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition.

2. Synaptic transmission
While the flow of a signal along (within) a neuron is electrical, the signal between neurons is chemical.
This transmission happens at a synapse.
A synapse is a specialised ‘gap’ between neurons through which the electrical impulse from the neuron is transmitted chemically to another neuron.
When the electrical impulse reaches the end of the neuron (the pre- synaptic terminal) it triggers the release of a neurotransmitter from tiny sacs called synaptic vesicles.

3. Neurotransmitter (NT)
Brain chemicals released from the synaptic vesicles that relay signals across the synapse from one neuron to another.
Can be divided into those that perform an excitatory function and those that perform an inhibitory function.
Can you think of any examples from the biological approach?

4. What happens?
Each neurotransmitter has its own specific molecular structure that fits perfectly into a post-synaptic receptor site, similar to a lock and a key.
When the right key (i.e. neurotransmitter) meets the right lock (i.e. receptor) a specific ion channel in the membrane is opened.
Ions then flow through the membrane into the neuron along their specific pathways.
This flooding of ions can cause an ‘action potential’ in the dendrites.
These action potentials can be excitatory or inhibitory

5. Excitation/Inhibition
Excitatory – When a NT increases the positive charge of the postsynaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse. E.g. adrenaline. Inhibitory – When a NT increases the negative charge of the postsynaptic neuron. This decreases the likelihood that the neuron will fire and pass on the electrical impulse. E.g. serotonin.