Neurotransmitters… they don’t sound particularly exciting, do they?
Well stick with us, because we think you might be impressed. These powerful chemicals in your nervous system affect how you think, feel and behave. In other words, they are integral to how you function.
From neural sacs to panic attacks, this brainstorm guides you through six fascinating facts about these extraordinary substances.
1) Neurotransmitters are biochemical messengers in your brain
As you might have guessed by the name, neurotransmitters ‘transmit’ information between nerve cells (or neurons). Because nerve cells are not in direct contact with each other, the neurotransmitters do this by crossing the synaptic cleft between the end of nerve cells (synapses).
Electrical signals are unable to cross this gap, and so they instead turn into chemical signals. Once the signals reach the next nerve cell they bind to its receptors and induce electrical signals.
The body of a nerve cell is divided into three components: a nucleus, a dendrite and an axon. The latter two parts are integral to neurotransmitters. In basic terms, the dendrite takes in information while the axon sends information out.
As well as relaying messages within the nervous system, neurotransmitters trigger responses for organs and cells, such as muscle contraction or release of hormones. And all this is constantly happening without you even knowing it.
2) Neurotransmitters are carried within small bubble-like ‘sacs’
These are called synaptic vesicles.
Like the Royal Mail bags that deliver your repeat prescription, these small sacs carry a neurotransmitter between and around the inside of a neuron. These are vital for the neurotransmission process and are recycled by nerve cells.
Generally speaking, there are two types of synaptic vesicle. Small clear-core vesicles are roughly 40 to 60 nm (nanometres) in size, while large dense-core vesicles are roughly between 90 and 250 nm in diameter. The size and structure depends on the type of neurotransmitter they are carrying.
3) We don’t know how many neurotransmitters there are
Released by the billions - yes, billions - of neurons in your brain, the total number of neurotransmitters is so astronomical that we have no way of measuring it. It’s almost comparable to counting the stars in a galaxy: we know there are vast amounts, but we can never be sure just how many.
Because there are hundreds of different types of neurotransmitters, there is no universally agreed upon way of classifying them. Perhaps the most common way to categorise neurotransmitters is to divide them up into four groups based on their molecular structure. These groups are:
- Amino acids. There are lots of different types of amino acids but only a few of them function as neurotransmitters in the nervous system: primarily glutamate, GABA, aspartic acid, and glycine.
- Peptides. These are much larger molecules than all the other types of neurotransmitters. Examples of peptides include vasopressin, somatostatin, and neurotensin.
- Monoamines. These organic molecules are also known as biogenic amines. Examples include norepinephrine (noradrenaline), dopamine, and serotonin.
- Other neurotransmitters.
New neurotransmitters are continuously being discovered, so it’s likely that this list may become more expansive in the upcoming years.
4) Different neurotransmitters have different functions
Neurotransmitters will either be excitatory or inhibitory (or some, like acetylcholine, can be both). Excitatory means they will likely stimulate a response or action, while inhibitory means they’re likely to inhibit a response or action. Here’s what the primary neurotransmitters do.
Glutamate plays a part in several transmission pathways and is involved with learning and memory.
Dopamine is a ‘focus’ neurotransmitter that regulates motor behaviour, motivation, pleasure, and emotional arousal. Elevated dopamine levels have been associated with schizophrenia, while low levels can be associated with addiction, cravings, certain forms of depression, and the muscular rigidity and tremors found in Parkinson’s disease.
Epinephrine (adrenaline) is involved in energy and glucose metabolism. Low levels of epinephrine are associated with depression.
Norepinephrine (noradrenaline) is used in the ‘fight or flight’ response.
GABA (gamma-Aminobutyric acid) inhibits anxiety and stress. Too little GABA is associated with anxiety and anxiety disorders. Some antidepressants can increase levels of GABA at the receptor sites.
Endorphins are affiliated with feelings of euphoria and reduce perception of pain in the body. Increased levels of physical activity such as exercise causes a release of endorphins. This may help to alleviate symptoms of depression.
Serotonin influences mood, sleep, and appetite (including carb cravings), and plays a role in impulsive and aggressive behaviour. Too little serotonin is associated with depression and some anxiety disorders such as obsessive-compulsive disorder (OCD).
Acetylcholine is involved in voluntary movement, learning, memory, and sleep. Low levels of acetylcholine are associated with the symptoms of depression, while low levels in the hippocampus (a part of the brain linked to memory) have been associated with dementia.
5) Neurotransmitters have a profound effect on your health and wellbeing
Neurotransmitters function primarily in the body’s Central Nervous System (CNS) and regulate physical and emotional processes such as mental performance, emotional state, physical energy, and pain response.
They are present throughout your body and are active anywhere where there are nerves, such as a your gut and muscles. When your neurotransmitters are healthy and in balance they will give your mind and body a real boost: you’ll think more clearly, feel less anxious, and enjoy a positive outlook.
There are various ways to help manage a chemical balance/imbalance, from maintaining a healthy diet and lifestyle to undertaking pharmaceutical treatment with medication such as antidepressants. This can differ from person to person, however, and some people have deficiencies and disruptions in certain neurotransmitters due to genetic or medical reasons.
6) Antidepressants affect neurotransmitters
Antidepressants are thought to work by elevating neurotransmitter levels in the brain. This is important because a neurotransmitter imbalance can cause common symptoms, including:
- Adrenal dysfunction (fatigue, insomnia)
- Addiction and dependency
- Loss of mental focus (attention deficit hyperactivity disorder (ADHD), mental fog etc.)
- Loss of appetite control
- Hormone imbalances
- Mood disorders such as depression or anxiety
Some antidepressant medications of the SSRI (selective serotonin reuptake inhibitor) antidepressant class increase the availability of serotonin at the receptor sites in the nervous system. SNRIs (serotonin and noradrenaline reuptake inhibitors) also increase the availability of the neurotransmitter noradrenaline. These responses can help to increase mood and focus.
If you would like to learn more about how your antidepressants affect the way neurotransmitters behave, speak to your GP or pharmacist.
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Clinically reviewed by Pooja Raichura MRPharmS: 19/4/18
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