 The brain is composed of a network of neurons that transmit signals by propagating nerve impulses . The propagation of this impulse from one neuron 's synapse to another is typically controlled by neurotransmitters , though there are also electrical pathways between some neurons . Neurotransmitters can inhibit impulse firing ( primarily done by γ @-@ aminobutyric acid , or GABA ) or they can excite the neuron into firing ( primarily done by glutamate ) . A neuron that releases inhibitory neurotransmitters from its terminals is called an inhibitory neuron , while one that releases excitatory neurotransmitters is an excitatory neuron . When the normal balance between inhibition and excitation is significantly disrupted in all or part of the brain , a seizure can occur . The GABA system is an important target for anticonvulsant drugs , since seizures may be discouraged by increasing GABA synthesis , decreasing its breakdown , or enhancing its effect on neurons . 
