What does "excitatory" mean when used in relation to responses caused by synapses?
Excitatory synapse means nerve impulse from presynaptic neuron jumps successfully to postsynaptic neuron through this synapse.
Neurotransmitters working at chemical synapse could be 'excitatory' or 'inhibitory'.
In this kind of sinus:
- impulse reaches presynaptic neuron's axon terminal
- Ca ions flow inside the synaptic knob from outside
- secretory vesicles containing neurotransmitters burst
- neurotransmitters are released in synaptic cleft
- neurotransmitter molecules attach to specific receptors present on postsynaptic membrane
In case of excitatory synapse, now Na channels will open up in the postsynaptic membrane. Flooding of inside of nerve cell by positive ions will generate a new action potential in the postsynaptic neuron. Thus nerve impulse continues to travel in postsynaptic neuron.
(On the other hand, in case of inhibitory synapse, Cl ions will enter the cell or potassium ions will flow out of the cell in response to binding of neurotransmitter. This prevents development of action potential in postsynaptic neuron.)