Final answer:
Glutamate is the excitatory neurotransmitter involved with arousal, vigilance, and mood, and its excess can cause anxiety problems.
Step-by-step explanation:
The excitatory neurotransmitter that is involved with arousal, vigilance, and mood, with an excess leading to anxiety problems, is glutamate. Glutamate is the main excitatory neurotransmitter in the central nervous system (CNS), used by about half of the neurons in the brain. It facilitates fast excitatory neurotransmission and is critical for cognitive functions such as learning and memory. An excess of glutamate can lead to overstimulation of the nervous system, potentially causing anxiety and excitotoxicity, which is damage to neuron cells due to excessive stimulation by neurotransmitters.