Excitation and Inhibition

• In reality, during synaptic transmission, many inhibitory and excitatory neurotransmitters are released; whether or not the post-synaptic neuron becomes positively or negatively charged simply depends on which type of neurotransmitter there are more of (this is called summation).
• Neurotransmitters have either an excitatory or inhibitory effect on the neighbouring neuron. For instance, the neurotransmitter serotonin causes inhibition in the receiving neuron, resulting in the neuron becoming more negatively charged and less likely to fire. In contrast, adrenaline (an element of the stress response which is both a hormone and a neurotransmitter) causes excitation of the post-synaptic neuron by increasing its positive charge and making it more likely to fire.