Those that do not fit the definition but play a role in eliciting complex responses are termed neuromodulators. Neurotransmitters have a life span of milliseconds in rapid communication, but modulators bring about biochemical changes over a period of minutes, hours, or days to affect learning, development, motivation states, or sensory and motor activities. Acetylcholine (ACh) is released from the terminals of vertebrate motor asonx, preganglionic terminals of the vertebrate autonomic system, from postganglionic terminals of the parasympathetic division of the autonomic system, and from the presynpatic terminals of some neurons of the certebrate CNS. There is also evidence that this also plays a large role in invertebrate neurons such as those found in mollusks and arthropods. Biogenic amines have been found concentrated in some nerve terminals, the synaptic vesicles of some nervous tissues, as well as some invertebrate neurons since they fluoresce in UV light after fixation with formaldehyde. Excitatory synapses use amino acids to a significant degree in the central nervous system whose receptors are ion channels for calcium and sodium or activate teh phopholipase C second-messenger system. Most neurotransmitters are made in the axon terminals with very few enzyme-mediated steps. Two or more linked amino acids comprise neuropeptides that are synthesized in neural tissue directed by mRNA and many of these function as communicators between the neural, endocrine, and immune systems. Gases simply diffuse from theri sites of origin in one cell to nearby cells. Nitric oxide serves are an intercellular message between neurons and between neurons and effector cells while carbon monoxide stimulates guanylyl cyclase.

Known or presumed neurotransmitters or neuromodulators chart:

• Acetylcholine (ACh):
  

  The most abundant neurotransmitter in the body and the primary neurotransmitter between neurons and muscles. The stomach, spleen, bladder, liver, sweat glands, blood vessels, and heart are just some of the organs that this neurotransmitter controls. The body's synthesis of acetylcholine is vital because of the neurotransmitters role in motor behavior and memory. Low levels of acetylcholine can contribute to lack of concentration and forgetfulness and may cause light sleep. The body synthesizes acetylcholine from the nutrients choline, lecithin, and DMAE, and ancillary nutrient cofactors, such as vitamins C, B1, B5, and B6, along with the minerals zinc and calcium. Acetylcholine helps control muscle tone, learning, and primitive drives and emotions. It also controls the release of pituitary hormone vasopressin, which is involved in learning and in the regulation of urine output.
  872k Animated Gif of Ach

• Catecholamines:
  • Dopamines (DA):
    

    Dopamine hasan inhibitor dampening activity so we stay rooted. Travels along pathways into the brain. Plays different roles: Dopamine in the basil ganglia (in brains interior) show they are critical for executing smooth and controlled movements. Lack of dopamine is a cause of parkinson disease which a person looses the ability to initiate controlled movements. Dopamine moves into frontal lobe regulating flow of information coming in from other areas of the brain. Compromise in the flow of dopamine may cause disrupted or incoherent thought as in schizophrenia. In milder disorders, too much dopamine in the limbic system and not enough in the cortex may produce an overly suspicious personality giving to bouts of paranoia or may inhibit social interaction. A shortage of Dopamine in the frontal lobes may contribute to poor working memory. Dopamine is also thought to produce feelings of bliss (the pleasure chemical). More dopamine into the frontal lobe lessens pain and increases pleasure.
    872k Animated Gif of Dopamine

  • Norepinephrine (NE):

    Norepinephrine - a hormone produced by the adrenal medulla, similar in chemical and pharmacological properties to epinephrine (also a hormone secreted by the adrenal medulla in response to stimulation of the sympathetic nervous system). Norephinephrine and epinephrine are the two active hormones that cause some of the physiological expressions of fear and anxiety and have been found to be in excess in some anxiety disorders when a disturbance in their metabolism occurs.
    872k Animated Gif of Norepinephrine

  • Epinephrine (Epi):

    Epi is another hormone/NT that is produced and secreted by the adrenal gland (located above the kidneys). Also knon as Adrenaline, Epi's main effect is that of stimilation of the Parasympathetic NS. When secreted into the body, effects include: increased heart rate, increased metabolic rate, increased blood pressure and vasoconstriction. Epi is closly related structurally to Norepinephrine, but its effects are almost opposite.
    872k Animated Gif of Epinephrine

• Serotonin (5-hydroxytryptamine, 5-HT):

  Serotonin - a chemical, 5-hydrozytryptamine (5-HT), present in blood platelets, the gastrointestinal tract, and certain regions of the brain. It plays an important role in blood clotting, stimulating a strong heart beat, initiating sleep, fighting depression (prescription drugs that treat depression raise the brain's levels of serotonin) and causing migraine headaches in susceptible individuals (because of its ability to constrict blood vessels or cause them to spasm). Serotonin is synthesized from the amino acid L-tryptophan. Serotonin (and, therefore, L-tyrptophan) also serves as a precursor for the pineal hormone melatonin, which regulates the body's clock.
  872k Animated Gif of Serotonin

• Histamine

• Excitatory amino acids
  • Glutamate:
    872k Animated Gif of Glutamate
  • Aspartate
• Inhibitory amino acids
  • Gamma-aminobutyric acid (GABA):
    872k Animated Gif of GABA
  • Glycine
  • Taurine

• Endogenous opioids (endorphin, enkephalines, dynorphins)
• Substance P
• Somatostatin
• Vasoactive intestinal peptide (VIP)
• Cholescrystokinin
• Neurotensin
• Insulin
• Gastrin
• Glucagon
• Thyrotropin releasing homrone (TRH)
• Gonadotropin releasing hormone (GnRH)
• Adrenocortiocpiroic hormone (ACTH)
• Angiotensin II
• Bradykinin
• Vasopressin (antidiuretic hormone, ADH)
• Oxytocin
• Epidermal growth factor
• Prolactin
• Bombesin
• Motilin
• Peptide histidine isoleucine (PHI)
• Peptide histidine methionine (PHM)
• Secretin
• Neuropeptide Y (NPY)
• Peptide YY
• Pancreatic polypeptide
• Growth hormone releasing hormone (GHRH)
• Neurokinin A (substance K)
• Neurokinin B
• Interferon
• Interluekin I (IL-I)
• Thymosin
• Galanin
• Calcitonin gene-related peptide (CGRP)

• Gases
  • NO
  • CO
• Nucleotides
  • Adenosine
  • ATP
• Steriods
  • Aldosterone
  • Cortisol and other glucocorticoids
  • Progesterone
  • Estrogens (17beta-estriol)
  • Testosterone
• Prostaglandins (prostaglandin E)