Neurotransmittes- A Review and its types..

Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron (brain cell) to another 'target' neuron.^[1] Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane in the axon terminal, on the presynaptic side of a synapse. Neurotransmitters are released into and diffuse across the synaptic cleft, where they bind to specific receptors in the membrane on the postsynaptic side of the synapse.^[2] Many neurotransmitters are synthesized from plentiful and simple precursors, such as amino acids, which are readily available from the diet and which require only a small number of biosynthetic steps to convert.
Most neurotransmitters are about the size of a single amino acid, but some neurotransmitters may be the size of larger proteins or peptides. A neurotransmitter is available only briefly – before rapid deactivation – to bind to the postsynaptic receptors. Deactivation may occur due to: the removal of neurotransmitter by re-uptake into the presynaptic terminal; or degradative enzymes in the synaptic cleft. Nevertheless, short-term exposure of the receptor to neurotransmitter is typically sufficient for causing a postsynaptic response by way of synaptic transmission.
In response to a threshold action potential or graded electrical potential, a neurotransmitter is released at the presynaptic terminal. Low level "baseline" release also occurs without electrical stimulation. The released neurotransmitter may then move across the synapse to be detected by and bind with receptors in the postsynaptic neuron. Binding of neurotransmitters may influence the postsynaptic neuron in either an inhibitory or excitatory way. This neuron may be connected to many more neurons, and if the total of excitatory influences is greater than that of inhibitory influences, it will also "fire". That is to say, it will create a new action potential at its axon hillock to release neurotransmitters and pass on the information to yet another neighboring neuron
There are two kinds of neurotransmitters – INHIBITORY and EXCITATORY.  Excitatory neurotransmitters are not necessarily exciting – they are what stimulate the brain.  Those that calm the brain and help create balance are called inhibitory.  Inhibitory neurotransmitters balance mood and are easily depleted when the excitatory neurotransmitters are overactive.

Inhibitory Neurotransmitters

nSEROTONIN is an inhibitory neurotransmitter – which means that it does not stimulate the brain.  Adequate amounts of serotonin are necessary for a stable mood and to balance any excessive excitatory (stimulating) neurotransmitter firing in the brain.  If you use stimulant medications or caffeine in your daily regimen – it can cause a depletion of serotonin over time.  Serotonin also regulates many other processes such as carbohydrate cravings, sleep cycle, pain control and appropriate digestion.  Low serotonin levels are also associated with decreased immune system function.
GABA is an inhibitory neurotransmitter that is often referred to as “nature’s VALIUM-like substance”.  When GABA is out of range (high or low excretion values), it is likely that an excitatory neurotransmitter is firing too often in the brain.  GABA will be sent out to attempt to balance this stimulating over-firing.
DOPAMINE is a special neurotransmitter because it is considered to be both excitatory and inhibitory.  Dopamine helps with depression as well as focus, which you will read about in the excitatory section.

Excitatory Neurotransmitters

DOPAMINE is our main focus neurotransmitter.  When dopamine is either elevated or low – we can have focus issues such as not remembering where we put our keys, forgetting what a paragraph said when we just finished reading it or simply daydreaming and not being able to stay on task.  Dopamine is also responsible for our drive or desire to get things done – or motivation.  Stimulants such as medications for ADD/ADHD and caffeine cause dopamine to be pushed into the synapse so that focus is improved.  Unfortunately, stimulating dopamine consistently can cause a depletion of dopamine over time.
NOREPINEPHRINE is an excitatory neurotransmitter that is responsible for stimulatory processes in the body.  Norepinephrine helps to make epinephrine as well.  This neurotransmitter can cause ANXIETY at elevated excretion levels as well as some “MOOD DAMPENING” effects.  Low levels of norepinephrine are associated with LOW ENERGY, DECREASED FOCUS ability and sleep cycle problems.
EPINEPHRINE is an excitatory neurotransmitter that is reflective of stress.  This neurotransmitter will often be elevated when ADHD like symptoms are present.  Long term STRESS or INSOMNIA can cause epinephrine levels to be depleted (low).  Epinephrine also regulates HEART RATE and BLOOD PRESSURE