Modality Two<unk> s, norepinephrine and dopamine, act as neuromodulators in the central nervous system and as hormones in the blood circulation. The<unk>  norepinephrine is a neuromodulator of the peripheral sympathetic nervous system but is also present in the blood (mostly through "spillover" from the synapses of the sympathetic system). High<unk>  levels in blood are associated with stress, which<unk> n be induced from psychological reactions or environmental stressors such as elevated sound levels, intense light, or low blood sugar levels. Extremely high levels of<unk> s (also known as<unk>  toxicity)<unk> n occur in central nervous system trauma due to stimulation or damage of nuclei in the brainstem, in particular, those nuclei affecting the sympathetic nervous system. In emergency medicine, this occurrence is widely known as a<unk>  dump". Extremely high levels of<unk> <unk> n also be<unk> used by neuroendocrine tumors in the adrenal medulla, a treatable condition known as pheochromocytoma. High levels of<unk> s<unk> n also be<unk> used by monoamine oxidase A (MAO-A) deficiency, known as Brunner syndrome. As MAO-A is one of the enzymes responsible for degradation of these neurotransmitters, its deficiency increases the bioavailability of these neurotransmitters considerably. It occurs in the absence of pheochromocytoma, neuroendocrine tumors, and<unk> rcinoid syndrome, but it looks similar to<unk> rcinoid syndrome with symptoms such as facial flushing and aggression. Acute porphyria<unk> n<unk> use elevated<unk> s. Effects<unk> s<unk> use general physiological changes that prepare the body for physical activity (the fight-or-flight response). Some typical effects are increases in heart rate, blood pressure, blood glucose levels, and a general reaction of the sympathetic nervous system. Some drugs, like tolcapone (a central COMT-inhibitor), raise the levels of all the<unk> s. Increased<unk> s may also<unk> use an increased respiratory rate (tachypnoea) in patients.<unk>  is secreted into urine after being broken down, and its secretion level<unk> n be measured for the diagnosis of illnesses associated with<unk>  levels in the body. Urine testing for<unk>  is used to detect pheochromocytoma. Function in plants "They have been found in 44 plant families, but no essential metabolic function has been established for them. They are precursors of benzocphenanthridine alkaloids, which are the active principal ingredients of many medicinal plant extracts.<unk> s have been implicated to have a possible protective role against insect predators, injuries, and nitrogen detoxification. They have been shown to promote plant tissue growth, somatic embryogenesis from in vitro cultures, and flowering.<unk> s inhibit indole-3-acetic acid oxidation and enhance ethylene biosynthesis. They have also been shown to enhance synergistically various effects of gibberellins."
Catecholamine
Octopamine
Synephrine
Dopamine 
Dopamine
Serotonin
Somatostatin
Neuropil