Download biopsychology-2-synaptic-transmission

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.
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 presynaptic terminal) it triggers the release of a neurotransmitter from
tiny sacs called synaptic vesicles.
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?
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
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.