Glossary of Terms:
Neurotransmitters are chemicals that are released at nerve endings in the brain where one nerve cell is close to another. They allow messages to pass from one cell to the next and are essential for communication between cells. A balance between neurotransmitters that excite and those that are calming maintains healthy brain function.
Dopamine (Dopa) - Dopa is a down-stream product in the conversion pathway of phenylalanine → tyrosine → dopa → dopamine. Dopa, unlike dopamine, can cross the blood brain barrier. Dopamine is involved in motor function and cognitive and behavioral function in the frontal regions of the brain cortex. This is where the so called “executive functions” are controlled. These include planning, inhibition, and organization among others. Nerves connect the frontal cortex with other parts of the brain that control movement. A limited amount of dopamine is also produced in the adrenal glands.
Norepinephrine (nor-adrenaline) - Both norepinephrine and epinephrine are neuro-hormones produced by the adrenal glands. However, only 20% of the available norepinephrine is produced in the adrenal glands. The rest is produced in sympathetic nervous system. Therefore, the effects of norepinephrine are largely mediated by the autonomic nervous system which controls involuntary movements such as digestion. NE produces constriction in practically all the blood vessels in the body.
Epinephrine (adrenaline) is solely produced by the adrenal glands and it is released in response to a perceived threat to the body. It produces cardiac stimulation, constriction or dilation of blood vessels, and bronchial relaxation. Epinephrine can bring about metabolic effects by breaking down stored glycogen and causing dilation of bronchiolar smooth muscles. It can produce vasodilation of the blood vessels that supply skeletal muscles and the heart. This enables a “fast get away” when threatened. Chronic stress causes the “fight-or-flight” mechanism to stick in overdrive. Eventually the adrenal glands become weakened and this results in dampened immune response, slowed cognitive function and digestive problems.
Motor Function refers to brain control of muscle movement and decision making. For example, when perceiving danger, our brain evaluates what we need to do in nano seconds. Then it sends messages to the appropriate muscles to move the body away from danger. Motor function is carefully evaluated by PET (positron emission tomography)scan or MRI (magnetic resonance imaging) to help determine the cause of movement problems.
Neuro Hormones - In the tissues, neurotransmitters may do double duty as neurohormones. For example, dopamine and epinephrine act as neurotransmitters in the central nervous system and as hormones in the bloodstream.
Adaptogen is a term applied to nutrients or herbs that help keep the body stabilized so that it can reduce the effects of stress. The amino acid tyrosine is adaptogenic and so is the herb Ashwagandha (Withania somnifera).