Inhibitory synapses

• Inhibitory synapses make it less likely that an action potential will be created on the postsynaptic neurone.
• In an inhibitory synapse, firstly the presynaptic neurone will release a type of neurotransmitter that binds to chloride ion protein channels on the postsynaptic membrane, triggering these channels to open.
• Once the chloride ion protein channels have been opened, chloride ions will move into the postsynaptic neurone via facilitated diffusion.
• The binding of the neurotransmitter to the postsynaptic membrane will also trigger the potassium ion channels to open. This causes potassium ions to move out of the postsynaptic neurone and into the synapse.
• The combined effect of the K+ ions moving out of the postsynaptic membrane and the Cl- ions moving into the postsynaptic membrane means that inside the membrane is more negative and outside is more positive.
• During the function of an inhibitory synapse, the postsynaptic membrane potential may reach up to -80mV compared to the usual -65mV at resting potential. This is known as hyperpolarisation.
• Hyperpolarisation in the postsynaptic neurone makes it less likely that a new action potential will be generated since a larger influx of sodium ions is needed to produce one.