Neurotransmitters and Diseases – Neuroscience Perspective
There are approximately 80 billion neurons in the human nervous system interconnected through trillions of synapses. These neurons communicate with one another, and with muscle cells and gland cells, by releasing chemical messengers called “Neurotransmitters”. These neurotransmitters are involved in countless functions of the nervous system and in controlling bodily functions. They play a major role in the functioning of the body in everyday life.
There are also other chemicals in the body called “Hormones” that are produced by the endocrine glands. Unlike neurotransmitters that are passed through the synaptic connections towards the target neurons, the hormones are passed through the bloodstream towards the target body parts. We will cover the hormones and endocrine system in our next post. It is important to note that some chemicals are both neurotransmitters and hormones e.g. norepinephrine, epinephrine, oxytocin.
The neurotransmission between two neurons happens through a gap between the synapses of neurons (called Synaptic Cleft). The electrical signals from the sending neuron are converted into chemical signals through the release of neurotransmitters. This causes a specific response in the receiving neuron.
A neurotransmitter influences a target neuron in one of the following three ways:
- Excitatory – An excitatory transmitter promotes a particular action in the receiver neuron. An excitatory neurotransmitter activates a specific region of the brain. The acetylcholine, epinephrine, glutamate, dopamine are excitatory neurotransmitters.
- Inhibitory – An inhibitory transmitter prevents any action in the receiver neuron. An inhibitory neurotransmitter depresses a specific region of the brain. The Gamma-Aminobutyric acid (GABA) is an inhibitory neurotransmitter. It acts as a brake to the inhibitory neurotransmitter.
- Modulatory – Neuromodulators act differently. They are not restricted to a specific synaptic cleft between two neurons but affect a large number of neurons at any given time. They generally work at a slower pace than excitatory and inhibitory transmitters. The dopamine, serotonin, acetylcholine, norepinephrine are some examples of neuromodulators.
All three types of neurotransmitters are required for a healthy living. They should be present in a good balance between them – called a chemical balance of the brain. They all need to be secreted at the proper time and in a proper amount for normal functioning, and good health of the body and mind. The practice of Yoga is helpful in attending such a balance – which we will cover in detail in a future post. Any imbalance in these chemicals will disturb the brain activities resulting in diseases.
Earlier the neuroscientists thought that a neurotransmitter has a single role or function e.g. the dopamine plays a role in pleasure, and GABA is a learning neurotransmitter. But now it is known that they are quite complex and multi-faceted. They work with, or against, each other to facilitate neural signaling across the nervous system (particularly those in the brain). The neuroscientists are still discovering a lot of things about neurotransmitters.
Also, different regions of the brain often rely on different neurotransmitters. For example, the prefrontal cortex (the cognition part of the brain) relies a lot on the serotonin and norepinephrine to function properly. Whereas the striatum (a part of the basal ganglia in the limbic system) depends mostly on the dopamine. We covered in the part of the brain in the previous post titled “Understanding Central Nervous System – Brain and Spinal Cord”.
In this post, we will cover only those neurotransmitters that are of interest to us from the perspective of Yoga practice and Yoga therapy for diseases related to neurotransmitters.
There are many different ways to classify neurotransmitters. One of such classifications divides neurotransmitters in:
- Amino Acids
Amino acids are the most abundant neurotransmitters in the brain. Technically, an amino acid is an organic molecule that is made up of a basic amino group (−NH2), an acidic carboxyl group (−COOH), and an organic R group (or side chain) that is unique to each amino acid. The important amino acids are Glutamate and Gamma-Aminobutyric acid.
It is an excitatory neurotransmitter in the cerebrum part of the brain. It is important in learning and forming memories by stimulation of the glutamatergic neurons in the hippocampus and cortex.
Excess of the glutamate in the brain is associated with neurological diseases such as Parkinson’s disease, Multiple Sclerosis (MS), Alzheimer’s disease, Stroke, ALS (amyotrophic lateral sclerosis or Lou Gehrig’s disease). Too little of glutamate in the brain leads to a coma. Excessively high but non-lethal levels of the glutamate in certain areas of the brain are strongly associated with schizophrenia.
Problems in making or using the glutamate is linked to a number of mental health disorders like Autism, Schizophrenia, Depression, Obsessive-compulsive disorder (OCD).
Gamma-Aminobutyric acid (GABA)
GABA is an inhibitory neurotransmitter of the glutamate, which is an excitatory neurotransmitter. GABA also plays an important role in brain development. Anyone with addiction (of alcohol, drugs, tobacco, caffeine, and food) is known to lack GABA.
GABA is linked to feelings of relaxation and reduction of anxiety. Not having enough of this important chemical can create an array of psychological problems like Anxiety, Nervousness, Racing thoughts, Hypertension, Chronic pain, Irritable bowel syndrome (IBS), Seizures, and Insomnia. While an excess of GABA can result in disorders like Depression, Hypersomnia.
The monoamine neurotransmitters are involved in the regulation of processes such as emotion, arousal, and certain types of memory. The important monoamines are the dopamine, norepinephrine, epinephrine, serotonin.
The dopamine is often referred to as the “pleasure” or “reward” neurotransmitter. It is released when you receive a reward in response to your behavior. It has effects that are both excitatory and inhibitory.
It increases enjoyment and is necessary for changing bad habits. It plays a significant role in human behavior and cognition – particularly in the brain’s reward system to help reinforce certain behavior that results in pleasure/reward. For example, it is due to a surge of the dopamine that prompts you to take the second slice of pizza. Actually, everything pleasurable releases dopamine in the nucleus accumbens (a region in the basal ganglia of the limbic system). Sex, drug, chocolates, winning money releases dopamine.
In addition to the rewards, the dopamine is also involved with motivation, decision-making, movement, attention, working memory, and learning.
Any dysfunction in the dopamine system leads to bad habits and a lack of enjoyment. Depression is often accompanied by bad habits such as impulsiveness, poor coping skills, addiction, and procrastination. This is because of the lack of dopamine.
The dopamine is also important for sleep. It helps modulate deep sleep and REM sleep – both critically important stages of sleep. In fact, not only dopamine affects sleep (as well as on pain and depression) but sleep, pain, and depression all also affect the dopamine system.
The benefits of gratitude start with the dopamine system because feeling grateful activates the brain stem region that produces dopamine. Additionally, gratitude toward others increases activity in social dopamine circuits, which makes social interactions more enjoyable.
The dopamine plays a role in Parkinson’s disease, addiction, Schizophrenia, Restless legs syndrome, Attention Deficit Hyperactivity Disorder (ADHD) and other neuropsychiatric disorders. For this reason, it is one of the most extensively studied neurotransmitters by neuroscientists.
It is also called Noradrenaline. It is both a neurotransmitter and a hormone. It is the primary neurotransmitter responsible for activating the stress response of the sympathetic nervous system (together with the epinephrine – covered below). It works on various organs in the body to control blood pressure, heart rate, liver function, and many other functions.
Norepinephrine helps us deal with stress, enhances thinking, focus. If someone is not getting enough sleep, it affects the production of norepinephrine receptors in the frontal cortex which is necessary for responding to stress.
Low levels of the norepinephrine can contribute to a variety of physical and psychological conditions like Attention Deficit Hyperactivity Disorder (ADHD), Depression, Fibromyalgia, Migraine, Insomnia, Low blood pressure. At the same time, high levels can cause Anxiety, Hypertension, Palpitation, and Headaches.
It is also called Adrenaline. Like norepinephrine, it is both a neurotransmitter and a hormone. It plays an important role in activating the stress response of the sympathetic nervous system (together with the norepinephrine).
Just like norepinephrine, low levels of the epinephrine can contribute to a variety of physical and psychological conditions like Attention Deficit Hyperactivity Disorder (ADHD), Depression, Fibromyalgia, Migraine, Insomnia, Low blood pressure.
High levels of epinephrine can contribute to conditions like High blood pressure, Anxiety, Palpitation, and Headache.
Chemically, the epinephrine and norepinephrine are very similar. The epinephrine works on both alpha and beta receptors and hence has a more wide-ranging effect. While norepinephrine only works on alpha receptors to increase and maintain blood pressure. Alpha receptors are only found in the arteries. Beta receptors are found in the heart, lungs, and arteries of skeletal muscles. While epinephrine has slightly more of an effect on the heart, norepinephrine has more of an effect on the blood vessels. Hence the epinephrine and norepinephrine have slightly different functions.
The serotonin is often called the “calming” neurotransmitter for its mood modulating effects. It has a profound impact on our mood – contributing greatly to our overall state of well-being.
It is also produced in the gastrointestinal tract in a large quantity. See the post titled “Do you know we humans have a second brain – The enteric nervous system”.
Serotonin improves mood, willpower, and motivation. In addition to the mood, it is known to help in managing appetite, sleep, memory, decision-making.
Serotonin deficiency is associated with several psychological problems. Some of them are Anxiety, Obsessive-Compulsive Disorder (OCD), Post-Traumatic Stress Disorder (PTSD), Depression, Insomnia.
The peptides are the compound consisting of two or more amino acids linked in a chain, the carboxyl group of each acid being joined to the amino group of the next by a bond of the type -OC-NH-. The main peptide of our interest is the oxytocin.
The oxytocin is both – a hormone and a neurotransmitter. It is is involved in childbirth and breast-feeding. It is also associated with empathy, trust, sexual activity, and relationship-building. It promotes feelings of trust, love, and connection. It helps in reducing anxiety.
Low oxytocin levels have been linked to autism and autistic spectrum disorders (e.g. Asperger syndrome). A key element of these disorders is poor social functioning. A low level of oxytocin is also linked to depression.
A high level of oxytocin is believed to be linked to benign Prostatic Hyperplasia, a condition that affects the prostate in almost half of the male population over the age of 50. This causes difficulty in passing urine.
The acetylcholine is an interesting neurotransmitter. But it does not fall in any of the three categories. It was the first neurotransmitter discovered by neuroscientists. It works primarily on the muscles and is found throughout the nervous system. It is released by the motor neurons in the brain to translate our conscious intention into the actual actions by the body muscles. This means, when you want to make a move, you depend on the release of ACh from your motor neurons to those muscles to make that move. This includes walking, talking, typing, and even breathing. It also has other roles in the brain like attention, arousal, and memory. It also plays a key role in facilitating neuroplasticity across the cortex. We will discuss neuroplasticity in a future post.
The main disorders associated with Ach are Alzheimer’s disease and Myasthenia gravis.
Yoga and Neurotransmitters
Yogasana practice is known to release all these good neurotransmitters – particularly the serotonin, dopamine, and norepinephrine – and keep them in a good balance. The effects of various Yogasana poses and Pranayama techniques on each of these neurotransmitters deserve a separate post. So stay tuned!
A few high-level principles before we conclude this post:
- Active Yogasana poses that stimulate the sympathetic nervous system will increase levels of the norepinephrine, epinephrine and reduce the excess level of GABA.
- Restorative Yogasana poses that stimulate the parasympathetic nervous system will increase the level of GABA, and reduce the levels of the norepinephrine, epinephrine.
- Regular Yogasana practice will a good mix of active and restorative Yogasana will provide you with a required dose of the serotonin to keep your mood high throughout the day.
- Eat a healthy and well-balanced diet. The regular practice of Supta Baddha Konasana will keep the enteric nervous system healthy and Gut-Brain axis in good shape. The majority of the serotonin is produced in the gut!
- 20 minutes of cooling down is important.
- Also, it is important to have proper sleep in keeping a good balance of neurotransmitters. Poor sleep will reduce the serotonin, dopamine, and norepinephrine production – particularly affecting the prefrontal cortex and hippocampus – the parts responsible for cognition and memory. Read about sleep habits, sleep stages, brain waves and Yoga therapy for insomnia in our previous posts.
Please note that the information contained in this website and blog posts is not a health or medical advice. Always consult a qualified medical professional or qualified health provider regarding any questions you may have about a medical condition.