chemical messengers that carry signals across the synaptic gap
can be excitatory and inhibitory
excitatory neurotransmitters
(eg. acetycholine and noradrenaline) are the ''on switches''
increases the likelihood of firing of the post-synaptic neuron by creating an electrical change in the membrane of the cell;
creates an excitatory post-synaptic potential (EPSP)
inhibitatory neurotransmitters
(eg, serotonin and GABA) are ''off switches''
decreases the likelihood of neuron firing;
creates an inhibitory post-synaptic potential (IPSP)
a nerve cell can recieve both EPSPs and IPSPs at the same time; summation (adding up the input) determines whether the cell fires
strength of EPSP can be increased spatial summation (a large number of EPSPs are generated at many different synapses on the same post-synaptic synapse at the same time)
and temporal summation (large number of EPSPs are generated at the same synapse by high frequency action potential on the presynaptic neuron)
