The Nervous System:
The nervous system is made up of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of nerves, which connects the CNS to all parts of the human body.
There are 3 different types of nerves, which are characterised by the direction in which they transmit an electrical impulse (signal):
Motor or efferent nerves: transmit information from the brain to the body.
Sensory or afferent nerves: transmit information from the body to the brain.
Spinal nerves: function as both motor and sensory nerves and are therefore called mixed nerves.
The nervous system (specifically the PNS) is divided into the autonomic nervous system - which is further subdivided into the sympathetic nervous system (SNS) and the parasympathetic nervous system (PSNP). The sympathetic nervous system, also known as “fight or flight”, is activated when we are in a stressful state, while the parasympathetic nervous system, also known as “rest and digest” is activated when we are in a relaxed state.
The enteric nervous system functions to control the gastrointestinal system (digestion only).
Both the autonomic nervous systems (SNS + PSNP) and the enteric nervous system function involuntarily - without our own conscious control.
At the cellular level, the nervous system is defined by a special type of cell called, the neuron, also known as a "nerve cell". Neurons send electrical impulses (signals) in the form of electrochemical waves, which travel along thin fibres called axons. These impulses, cause neurotransmitters to be released at gap junctions (the tiny spaces between all neurons) called synapses. The transmission of electrical impulses and chemical neurotransmitters from one neuron to another, may either excite, inhibit, or otherwise modulate receiving neurons.
The nervous system – facts:
The size of the nervous system ranges from a few hundred cells in the simplest worms, to around 300 billion cells in African elephants.
Nerve signals are created via action potentials (AP). When the AP arrives at the synapses, the message is mediated by chemicals (neurotransmitters).
Nerve cells are rich in mitochondria (the battery - energy source - within all cell).
The CNS uses glucose as its primary fuel.
There are receptor sites in the brain for other circulating hormones, such as; cortisol, oestrogen, progesterone and thyroid hormones, so all of these can have a direct effect on brain function.
There are over 50 substances recognised as molecules that function as neurotransmitters including; cytokines, peptides, nitric oxide and neurotrophic factors.
Neurotransmitters (NTs) include; serotonin, GABA, catecholamines (noradrenaline, adrenaline, dopamine), acetylcholine.
NTs regulate the strength of the action potential (AP) - at the synapse (between two neurons) – each AP will have either an excitatory or inhibitory effect.
NTs exert their effect by binding to specific receptor sites, located on the membrane of post synaptic neurons.
Once the action potential (AP) has been transmitted from one neuron to the next, the NTs detached from their specific receptor sites and are either rapidly reused or otherwise broken down by enzymes.
The body absorbs tryptophan (essential amino acid) from dietary sources and converts it into 5-HTP and then into serotonin. Therefore, dietary levels of tryptophan can affect serotonin production.
The two enzymes involved in the production of serotonin include; tryptophan hydroxylase and aromatic acid decarboxylase.
Serotonin is produced and acts locally in both the CNS and GIT (digestive system).
Chronic stress (HPA axis activation) causes hyper-secretion of stress hormones; ACTH and cortisol, which alter serotonin receptors and therefore, reduce the ability of serotonin to bind to them.
Low serotonin levels are associated with:
Obsessive compulsive disorders
Substances which naturally increase endogenous serotonin levels include:
Tryptophan (essential amino acid)
5-HTP (extracted from the seeds of the plant Griffonia simplicifolia).
(nutrients needed to allow for proper enzymatic function):
Tryptophan hydroxylase: B3, Folic acid, Calcium, Iron
Aromatic acid decarboxylase: B6, vitamin C, Zinc, Magnesium
Glutamate and GABA
Glutamate is the major excitatory neurotransmitter in the brain.
GABA is the major inhibitory neurotransmitter in the brain.
L-glutamine is a conditionally essential amino acid, produced by the body and is also found in dietary protein sources. L-glutamine is first converted into glutamate using the enzyme glutaminase and then further into GABA, using the enzyme glutamate decarboxylase.
Both glutamate and GABA have a yin- yang relationship in functioning and therefore, low GABA will cause an increased production in glutamate to compensate.
(nutrients needed to allow for proper enzymatic function):
Glutamate decarboxylase: B6, vitamin C, Zinc, Magnesium
Low GABA is associated with:
Anxiety/ panic attacks
Alcohol and carbohydrate cravings
Other types of neurotransmitters:
Glycine (conditionally essential amino acid): reduces glutamate (anxiety) and increases GABA (relaxation).
Taurine (conditionally essential amino acid): reduces glutamate (anxiety) and increases GABA (relaxation).
Catecholamines (dopamine, noradrenaline, adrenaline): major neurotransmitters found in the SNS: associated with arousal, stress response, memory and motivation. L-phenylalanine (essential amino acid) is converted into L-tyrosine and then into Dihydroxyphenylalanine, which is further converted into dopamine. When blood pressure drops dopamine is converted into noradrenaline and when blood glucose drops or during states of stress, noradrenaline is converted into adrenaline. Cofactors needed by the enzymes of this pathway include; B1, B3, iron, B6).
Acetylcholine: major neurotransmitter found in the PSNS: Associated with learning, memory, cognitive processing, autonomic function and fine motor control. Acetylcholine is made from combining choline with acetyl CoA (glucose metabolite).
Mental health disorders:
A holistic approach to mental health - emphasises the importance to connect the biological abnormalities of an illness with its social context and therefore, the biopsychosocial model, is based upon a combination of biological, psychological and social factors. This approach highlights the failure of the medical model to appreciate the complexity of this disorder. Antidepressants, commonly perscribed in western mainstream medicine, treats depression locally - as a brain dysfunction - and has a modest 46% response rate at reducing depression outcomes.
Drivers for depression:
Factors that may be mediating the development of depression include; poor methylation, inflammation (oxidative stress), neurotransmitter imbalances (brain dysfunction), insulin resistance, nutritional deficiencies, hormonal imbalances and dysregulated circadian rhythm.
Risk factors for depression:
Single nucleotide polymorphism (SNPs) - genetic predisposition, a history of anxiety, female gender, major life events (stress), chronic health concerns (medication side effects), antibiotics (dysbiosis - imbalance between good and bad bacteria in the gut - microbiology), sedentary lifestyle, substance abuse, eating disorders, physical, sexual or psychological abuse/ trauma, poor nutrition, sleep deprivation and environmental exposure to neuroendocrine disruptors (PCBs, PAH, Phthalates, BPA, heavy metals and pesticides).
Insomnia can be divided into two types:
Sleep onset insomnia (difficulty falling asleep) and may be caused by: anxiety/ fear, high cortisol (stress).
Sleep maintenance insomnia (waking up frequently throughout the night or consistently waking up early) and may be cause by: low blood glucose levels, alcohol, depression, high cortisol (stress).
The enzyme, N-acetyltransferase, converts serotonin into N-acetyl serotonin, which is further converted into melatonin by the enzyme HIOMT. Serotonin conversion into melatonin is increased during prolonged periods of darkness. Optimal melatonin production is between 10-11pm, staying up past this time suggests that you are under threat, your body will then respond by releasing cortisol (stress hormone) into your bloodstream which inhibits melatonin production and activates your sympathetic nervous system (fight or flight). When you eventually go to sleep (eyes closed - prolonged darkness), your liver will break down the excess cortisol and stimulate melatonin production - although less effectively.
In the CNS, the major mediators of the symptoms of anxiety appear to be noradrenaline, serotonin and corticotropin-releasing factor (CRF). CRF, is a peptide hormone involved in the human stress response (HPA axis). Its stimulates the pituitary gland to synthesise ACTH, which stimulates the adrenal glands to synthesise cortisol. In the short term, CRF suppress appetite, boosts attention and increases anxiety. CRF supresses the immune system via the action of cortisol, however, CRF itself can actually heighten inflammation.
In the PNS, the autonomic nervous system – specifically - the sympathetic nervous system (fight and flight activation), mediates many of the symptoms associated with anxiety.
Once upon a time, biologists believed that the neurons of the brain could not change or re-grow. However, it has now be found that the brain constantly repairs and remodels throughout our lives. There is a constant pruning and rewiring of synaptic ends, dependent on how we use our brain. Neuroplasticity can be induced by exercise, lowering cortisol (stress) and meditation.
Naturopathic Nutritional Therapy to support the nervous system:
1) Follow a modified Mediterranean diet; consisting of vegetables, fruit, whole grains, legumes, seafood (oily fish), unrefined oils (olive oil), raw unsalted nuts, seeds and poultry.
2) Due to conflicting research on the consumption of gluten, dairy and red meat with regards to inflammation, it is therefore advised to; eliminate or significantly reduce; dairy and gluten and limit lean red meat intake to one portion per week (1 portion = 65g).
3) This diet provides low GI foods, a high fibre content and lean proteins, which combined in every meal, has been shown to improve insulin sensitivity and blood glucose control, subsequently reducing inflammation and improving low mood, anxiety, stress and sleeping.
4) This diet is rich in precursor nutrients for neurotransmitter production; tryptophan (serotonin) and taurine (GABA enhancer) as well as conversion cofactors; B vitamins, calcium, iron, zinc and Magnesium.
5) Additionally, due to the high fruit and vegetable intake it is rich in many antioxidants including; A, C, E and selenium (brazil nuts), which greatly reduces inflammation (oxidative stress).
6) Legumes, seafood, poultry and brussel sprouts, provide a good intake of phospholipids (choline and lecithin) and vitamin D (fish, egg yolks, mushrooms).
7) Healthy oils such as; olive oil, coconut oil, flaxseed oil, sesame seed oil, avocado oil - provides anti-inflammatory omega fats which improves plasma membrane fluidity and therefore, nutrient absorption.
Foods to avoid:
Processed foods, refined grains, trans fats, sugars.
Refined oils: vegetable, soybean, sunflower, stafflower, cottenseed, peanut, corn, canola, rapeseed, hydrogenerated, margarine.
* Drug-nutrient interations may occur when taking any 'natural' supplements (regardless if its origin is food based or synthetically derived) alongside perscribed OR over the counter medications. Please do not take any of these without consulting your doctor or health care professional.*
5-HTP (supports low mood and sleeping by increasing serotonin and melatonin production).
Rhodiola (type of adaptogen which supports the adrenal glands by modulating cortisol and supporting low mood).
Magnesium (cofactor used in GABA production and therefore reduces anxiety).
Omega 3: EPA and DHA (potent anti-inflammatory properties has been shown to improve; insomnia, anxiety and low mood).
Methyl B-complex. (supports methylation which is needed for the production of all neurotransmitters (BH4 cycle) and serves as important cofactors for neurotransmitter conversion enzymes).
Vitamin D (deficiency is commonly associated with low mood).
Zinc (cofactor used in GABA production and therefore reduces anxiety and is also useful in additions).
Evidence suggests that chronic sleep deprivation is associated with changes in serotonin and CRH receptors as well as alterations in the HPA axis (stress response), which is associated with low mood and anxiety.
Yoga modulates neuroplasticity through its ability to increase BDNF, highlighting its limitless benefits.
Meditation, activates the parasympathetic nervous system (rest and digest) and therefore overtime it strengthens the body's relaxation response, which in turn reduces stress induced hyperarousal of the sympathetic nervous system (fight and flight). Meditation, activates the prefrontal cortex and increases alpha and theta brain waves, which is associated with improved attention, concentration and emotion regulation.
Exercise upregulates BDNF, which enhances neuroplasticity and promotes hippocampal neurogenesis (repair of nerve cells). Exercise increases noradrenaline, endorphins and tryptophan hydroxylase, which in turn increases serotonin levels and therefore, improves mental health, infinitely.