The Neuron Learning Map

Along with this post and this post, you will be able to learn about the neuron easily with this map. Click on the map to make it bigger. 

The Neuron - Part 3 - Neurotransmitters

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Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse.

There are many ways you can classify neurotransmitters. The easiest way to remember them is by dividing them into two groups: excitatory and inhibitory. Excitatory neurotransmitters stimulate the brain while inhibitory neurotransmitters create balance when excitatory neurotransmitters are overactive. 

They can also be divided into small molecule neurotransmitters and neuropeptide neurotransmitters. Small molecule neurotransmitters are more rapid and they are involved in the central nervous system prompt feedback like sensorial and motor signals.

Small Molecule Neurotransmitters

• Acetylcholine
• Dopamine
• Noradrenaline

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• Serotonin
• Histamine
• GABA
• Glycine
• Glutamate
• Aspartate

Neuropeptide Neurotransmitters

• Corticotropin releasing hormone
• Corticotropin ACTH
• Beta-endrophin
• Substance P
• Neurotensin
• Somatostatin
• Bradykinin
• Vasopressin
• Angiotensin II

I’ll just talk about a few of these neurotransmitters but I’ll give links to some resources if you want more.

Serotonin or 5-hydroxytryptamine (5-HT) plays an important role in a range of brain functions. It is derived from tryptophan and it is primarily found in the gastrointestinal tract, platelets and the central nervous system. 

Low serotonin levels lead to insomnia, anxiety, depression, panic attacks, obesity, eating disorders, chronic pain, migraines and alcohol abuse. Also, negative thoughts correlated with low self esteem or obsessive thoughts and behaviors could be symptoms of low serotonin levels. 

On the other hand, high serotonin levels could lead to Serotonin syndrome which has the following symptoms: hypomania, hallucinations, shivering, sweating, nausea, tremor, etc. 

More about serotonin syndrome here. 

Noradrenalin or norepinephrine has a double role: as a neurotransmitter and as a hormone. It is synthesized from dopamine. The release of noradrenaline increases the level of excitatory activity in the brain and the noradrenergic pathways are involved in the control of attention and arousal functions. Along with epinephrine it underlines the fight or flight response which directly increases the heart rate, increases blood flow to skeletal muscle and releases glucose from energy stores.

Dopamine is a key neurotransmitter that has important roles in behaviour and cognition, movement, motivation, sleep, mood, attention, memory, and even learning. It helps us with our motivation and our desire to get tasks done. ADD/ADHD or even caffeine are stimulants that help us focus more by manipulating dopamine levels.

Acetylcholine is a neurotransmitter in the peripheral nervous system and the central nervous system. It is very important for proper functioning of the nervous system and muscle functioning. 

If you would like to read more, check out this amazing website.

http://www.brainexplorer.org/neurological_control/neurological_neurotransmitters.shtml

Here’s a cool video about neurotransmitters:

Serotonin

Serotonin is a neurotransmitter linked to depression, especially medium or mild intensity depression. Serotonin levels drop during depression, so most antidepressants are build in the most selective manner. There are pills that react with presynaptic 5 HT 1A receptors.  They prevent the reuptake of serotonin by the presynaptic neuron, thus maintaining higher levels of 5-HT in the synapse. SSRI treatment (Selective serotonin reuptake inhibitors) is the first step in depression treatment. Here we have: Fluoxetine (our classic Prozac), Sertaline (Zoloft, another classic), Paroxetine, Fluvoxamine and Citalopram. Other medication reacts with postsynaptic receptors, and others on both groups. Their success is influenced by how they managed to increase the serotonin levels necessary for nerve impulse.

Serotonin and types of depression

When it comes to depression, the type that starts with low serotonin levels is an anxious depression with psychomotor agitation, frequent crying, irritability, irascibility, and a patient that will still struggle to get out of this state. There is no pathology at the cognitive level (perhaps some attention and concentration difficulties).

When we discuss about major depression, we must add that it is associated, besides low serotonin levels, with low noradrenaline levels. Some of the symptoms are: psychomotor inhibition, severe cognitive deficiencies, weight loss, oversleeping, even athymhormia.

Psychotic depression (appears in 15% of people who suffer from major depression). Symptoms include: auditory and visual hallucinations and delusional thinking (mood congruent delusions like paranoid delusions, delusions of guilt, delusions of persecution), thoughts of death, etc. As for neurotransmitters, besides serotonin and noradrenaline issues, there is a high increase of dopamine, which can be treated with narcoleptics or typical antipsychotics.

More on serotonin:

http://psychology.wikia.com/wiki/Serotonin

http://www.helpguide.org/mental/depression_signs_types_diagnosis_treatment.htm

Picture taken from here.