Excitatory and Inhibitory Neurotransmitter

Increase the likelihood that an excitatory signal is sent to the postsynaptic cell, which is then more likely to fire

• Decrease the likelihood of that neuron firing • Generally responsible for calming the mind and body, inducing sleep and filtering out unnecessary excitatory signals

Acetylcholine (ACh) and noradrenaline

Serotonin and GABA

Excitatory neurotransmitters bind with a postsynaptic receptor causes an electrical change in the membrane of that cell, resulting in an excitatory post-synaptic potential (EPSP), meaning that the postsynaptic cell is more likely to fire

Inhibitory neurotransmitters binding with a postsynaptic receptor results in an inhibitory postsynaptic potential (IPSP), making it less likely that the cell will fire

• A nerve cell can receive both EPSPs and IPSPs at the same time. • The likelihood of the cell firing is determined by adding up the excitatory and the inhibitory synaptic input • The net results of this calculation (summation) determines whether or not the cell fires

• In spatial summation, a large number of EPSPs are generated at many different synapses on the same postsynaptic neuron • In temporal summation, a larger number of EPSPs are generated at the same synapse by a series of high-frequency action potentials on the presynaptic neuron