NEUROTRANSMITTERS

Neurotransmitters are chemicals in the brain that pass signals by traveling from one neuron to another neuron or cell. Here are the basic steps in the movement of neurotransmitters:

1. Action potential reaches the synapse of the transmitting neuron.
2. Neurotransmitters present in the synaptic vesicles within the synapse of the transmitting neuron are released in the synaptic cleft.
3. Neurotransmitters from the transmitting neuron are bound to the receptors of the receiving neuron or cell.
4. A signal is generated in the receiving neuron or cell. 

There are many different types of neurotransmitters, some of the important ones are:

Acetylcholine: is the first and the most common neurotransmitter, isolated by German scientist Otto Loewi. Acetylcholine is abbreviated as ACh. It works both in the peripheral nervous system and central nervous system. In the peripheral nervous system, it activates muscles related to digestive, urinary, respiratory and cardiovascular systems. In the central nervous system, it is associated with memory and learning. Lack of acetylcholine in the brain is responsible for Alzheimer's disease.  Blocking Acetylcholine can cause Myasthenia Gravis, a disease where muscles are weakened and the body feels fatigued.

Glutamate: is the most abundant neurotransmitter in the brain. Glutamate is involved with memory and learning. It is also an excitatory neurotransmitter, meaning it's presence simulates parts of the brain. Glutamate is also toxic and an excess of it will kill parts of the brain. Excess of Glutamate in the brain is the cause for Lou Gehrig's disease.

GABA: also known as gamma Aminobutryic acid, is an inhibitory neurotransmitter. Which means that it prevents nearby neurons from getting excited. In other words, when an inhibitory neurotransmitter is received by a receptor, it blocks the action potential of that neuron, thus prevents it from firing excitatory neurotransmitter. People suffering from Anxiety disorder, Epilepsy or Huntington's disease lack in GABA.

Dopamine: is also an inhibitory neurotransmitter. Dopamine is associated with rewards mechanism in brain. Parkinson's disease is caused by a loss of dopamine producing neurons, on the other hand schizophrenia is caused by an excess of dopamine. Blocking dopamine receptors helps reduces psychotic symptoms. Dopamine also regulates the endocrine system by directing the hypothalamus to manufacture hormones and hold them in the pituitary gland.

Serotonin: is yet another inhibitory neurotransmitter. About 80% of human bodies serotonin is found in the gastrointestinal tract, where it controls the movement of the intestines. Remainder of it is found in the brain, where it is involved with sleep quality, mood and emotions. Lack of serotonin causes depression and intestinal disorders.

Norepinephrine: is both a hormone and a neurotransmitter. It is involved in memory and cognitive functions. It is released from the sympathetic nervous system and it increases our blood pressure and heart rate. Deficiencies in norepinephrine causes Alzheimer’s disease, Parkinson’s disease, and Korsakoff’s syndrome a cognitive disorder associated with chronic alcoholism.

Epinephrine: is also a hormone and a neurotransmitter. It is also known as adrenaline. It is responsible for attention, focus, cognition and arousal. Excess of epinephrine can cause ADHD, anxiety and sleep problems, where as lack of it can cause focus problems and fatigue.

Endorphin: falls in the category of peptides (short chains of amino acids that are linked together). The brain also makes peptide like neurotransmitters like endorphin. It acts like painkillers by preventing nerve cells from releasing more pain signals. It is produced by the pituitary glands and the hypothalamus during exercise and excitement. It is the neurotransmitter that lets animals hibernate.

Gaseous Neurotransmitters: neurotransmitters can also be in the form of gases. Two important ones are nitric oxide and carbon monoxide. Gases don’t work like normal neurotransmitters; they don’t have a reception site instead they just diffuse into other neurons.

Lipid Neurotransmitters: Lipids (naturally occurring organic compounds, like fats) like gasses can also function as neurotransmitters. Prostaglandins are a class of compounds made from lipids by an enzyme called cyclooxygenase. These molecules have powerful effects in inducing of fever and generation of pain, in response to inflammation. Aspirin reduces fever and lowers pain by inhibiting the cyclooxygenase enzyme.