Additional questions:

a) What role do the upper centers (eg, hypothalamus) play in phasic or tonic stimulation of the trigeminal nerve?

b) How independent are neurotransmitters such as serotonin in the stimulation of the trigeminal nerve?

c) Does the sequentially stimulated trigeminal nerve show habituation?

d) Do phasic and tonic changes occur in trigeminal nerve impulses during and at the end of the attack, especially in primary headaches such as migraine?

e) What changes occur in the amount of neurotransmitters that occur when trigeminal nerve impulses are phasic or tonic? Can these be measured?