INHIBATORY SYNAPSES

• Inhibitory neurotransmitter is secreted from the presynaptic neurone
• The inhibitory neurotransmitter binds to its receptors on the postsynaptic membrane
• Special potassium ion channel proteins open, allowing potassium ions (K+) to diffuse out of the postsynaptic neurone
• Chloride ion channels open, causing chloride ions (Cl-) to diffuse into the postsynaptic neurone
• The inside of the postsynaptic neurone becomes more negative, leading to hyperpolarization of the membrane
• The potential of the postsynaptic membrane is now more negative than resting potential
• More sodium ions would need to enter the postsynaptic neurone to reach threshold for an action potential
• An action potential is now much less likely in the postsynaptic neurone
• Some neurones are under the control of both an excitatory and an inhibitory synapse.

  The relative activity of each will determine whether or not a post-synaptic action potential will be generated.

  This is a form of spatial summation.