Understanding the nervous system
The nervous system is the body’s control centre, providing coordination between input to the brain and actions of the body. It can be thought of as the motherboard, which allows communication between the organs and systems of the body, so that internal homeostasis and health can be maintained.
A healthy nervous system is vital for health of the body and mind, a subject which is gaining more attention as links between stress and disease come to light and it is suggested that a high percentage of disease is linked to stress.
Stress is described as a “state of threatened homeostasis or disharmony” (1). The origin of stress can be what are termed as positive or negative. Some level of stress can be beneficial for health, and help to propel us on, but chronic unchecked stress is usually damaging. Chronic stress creates disharmony in physical and psychological function, disrupts health and sense of wellbeing, leads to a whole range of inflammatory responses, immune system dysfunction, and eventually disease states (2).
The nervous system works closely with the endocrine system to manage the body’s responses to stress.
This article will give an overview of the nervous system, and how the nervous and endocrine systems work together to manage response to stress. It will focus on supporting overall nervous system health, how to maintain healthy stress responses, and support recovery from the repercussions of excess stress with herbs and lifestyle measures.
Nervous system overview
The nervous system keeps order in the body in 3 main ways, which in simple terms are as follows:
- Sensory input from the rest of the body which travels to the central nervous system along sensory nerves.
- Integration the central nervous system processes information and responses are formulated.
- Motor output is the response from the central nervous system to the rest of the body which activates effectors (muscles or glands).
Structurally, the nervous system is categorised in two parts:
- The central nervous system: consists of the brain and spinal cord.
- The peripheral nervous system: consists of the peripheral network of nerve tissues which travel from the spinal nerves to the rest of the body.
The peripheral nervous system is further categorised according to these functions:
- Somatic Nervous System (SNS): refers to the voluntary control of skeletal muscles.
- Autonomic Nervous System (ANS): refers to involuntary control of smooth muscle, cardiac muscle, and glands.
The autonomic nervous system (ANS) has three parts:
- Sympathetic Branch: usually supports exercise of emergency action, in ‘fight or flight’ responses to stress or perceived stress.
- Parasympathetic Branch: usually supports ‘rest and digest’ activities, and more relaxed or passive states.
- Enteric nervous system (ENS): refers to nerves which are involved in the function of the smooth muscle, glands, and endocrine cells in the gastrointestinal tract. The ENS is also affected by the parasympathetic and sympathetic branches of the ANS.
The autonomic nervous system (ANS) is involved in managing stress in the body.
How do the nervous system and the HPA axis work?
The two main branches of the ANS, the sympathetic and parasympathetic, work together to ensure appropriate responses of the body. When working in harmony the activity between the sympathetic and parasympathetic branches will naturally fluctuate according to changing situations, ensuring regulation of certain bodily processes (3).
Some bodily functions regulated by the ANS include:
- Blood pressure
- Breath rate
- Heart rate
- Digestion
- Metabolism (affecting body weight)
- Body temperature
- Excretion (including urination and defecation)
- Sexual response
The following diagram shows an overview of ANS functions and where in the spine the nerves associated with each branch stem from.
From this diagram we can see how the sympathetic responses manifest as bodily changes we may experience when feeling ‘stressed’ such as a racing heart, sweaty palms, dry mouth, loss of appetite or upset digestion.
ANS responses to stress produce quick physiological changes, as the parasympathetic branch withdraws its inhibitory effects, facilitating the sympathetic ‘fight or flight’ response (4).
Two of the main chemical messengers involved in ANS responses are noradrenalin (also adrenalin), and acetylcholine. Noradrenalin tends to be involved in sympathetic responses, promoting wakefulness and arousal. Some of the physiological responses it creates include (5):
- Dilating pupils
- Increasing heartrate
- Constricting blood vessels
- Inhibiting peristalsis (movement throughout the intestines necessary for digestion).
Acetylcholine is usually involved in parasympathetic responses, and sometimes sympathetic depending on the synapse type (3).
The ANS works closely with another important mechanism involved in stress responses, called the HPA axis, to ensure a state of biological and behavioural preparedness for stressful situations, or stress stimulus (4).
The HPA axis is a communication network between the hypothalamus, pituitary, and adrenal glands, which bridges the nervous and endocrine systems. The endocrine system consists of glands and hormone messengers, which along with the nervous system help to maintain bodily functions, including responses to stress. The hypothalamus and pituitary gland are a part of the central nervous system located in the brain, and the adrenal glands are endocrine organs located above the kidneys.
The HPA axis acts as a signalling system with the function of optimizing performance attuned to circadian, environmental, and physiological demands (6). This response system redirects energy resources to meet real or anticipated demands, and therefore allows the body to adapt to stress (7).
In response to the stimulus of stress, a cascade of hormonal messengers are released throughout the neuro-endocrine system which the HPA axis traverses.
The production and release of steroid hormones are the result of this cascade, and cortisol, often referred to as the ‘stress hormone’ is the end product of the HPA axis cascade. Cortisol is released from the adrenal cortex into the bloodstream where it travels throughout the body to carry out its functions, such as making more glucose available as an energy source to deal with the demands of stress (8).
Understanding the root
Although the release of hormonal messengers such as cortisol is the end of the cascade of the HPA axis, it is not the end of the stress response, which can continue through a series of negative feedback loops.
Nowadays people often feel stressed because of various factors such as worries over job, finances, homelife, relationships, over-stimulation from social media or screen time, lack of sleep, lack of exercise. Stress hormones such as adrenalin and cortisol which are released into the system allow physical responses such as taking action in an emergency or running from a lion (e.g. literal fight or flight), these physiological changes would have once been life-saving to allow us to act accordingly in response to physical danger, and once this was resolved the body and nervous system would reset back to a resting state.
However, in the face of many modern stressors which are often of emotional or mental origin, and therefore not resolved by physical action, this in some way leaves these physiological stress responses surplus to requirement, and when the repeated perception of stress perpetuates these changes to our physiology, over time they can create health issues.
In summary, inappropriate or prolonged HPA axis activation is energetically demanding for the nervous system and body overall, and if left unchecked can lead to numerous physiological and psychological disease states such as a feeling of frazzled nerves, disturbed sleep, anxiety, high blood pressure, digestive issues, immune system issues, inflammation, blood sugar imbalances, diabetes (7).
Dysregulation of the stress response system has been associated with obesity, asthma, inflammation, and depression even among children and adolescents (4).
Therefore taking care of your nervous system health really is a key ingredient for overall health. There are many herbs which provide fantastic support for the nervous system to see you through or recover from stressful periods of life, which alongside appropriate lifestyle measures, and stress management, can reestablish or maintain optimum nervous system health.
Signs and symptoms
Common symptoms of HPA axis dysfunction
The list of symptoms may be very different from one person to another, but common symptoms include (8):
- Wake up tired, or feeling fatigue throughout the day
- Cognitive issues such as “brain fog”
- Trouble falling asleep
- Lower tolerance to stress, irritability, short temper
- Weight gain, especially in the midsection
- A weak immune system, getting sick more often
- Hair loss in women
- Low libido in men (80% of DHEA is produced by the adrenals and is involved in arousal)
Herbal solutions
Herbs can provide valuable support for the nervous system as a general maintenance to ensure its healthy function, as well as reestablishing balance in times of stress or illness. In both cases there are also lifestyle measure which will additionally support nervous system health, these can be found in the holistic solutions section.
When considering how to support the nervous system we can consider the following:
- Restoring and toning the tissues of the nervous system themselves
- Creating a calming effect to ease stress and its repercussions
- Increasing overall resilience to stress
- Regulating and supporting healthy stress responses by restoring healthy function of both the sympathetic and parasympathetic branches of the ANS, and of the HPA axis.
There are a few actions provided in the body by some herbs which support these aforementioned aspects of the nervous system in different ways from nourishing the tissues to helping regulate healthy stress responses.
Adaptogenic herbs increase the body’s resilience to and ability to adapt to stress, whether the stress is of physical, environmental, or emotional origin. Adaptogens promote healthy physiological function and help reduce the potentially detrimental effects of stress. Examples of adaptogenic herbs which can be helpful for the nervous system include ginseng, Siberian ginseng, ashwagandha and rhodiola.
Adrenal restoratives / Tonics are herbs which tone the tissues and improve the function of the adrenal glands, which contributes to healthier stress responses, and supports recovery after prolonged exposure to stress. Liquorice is an adrenal tonic herb as is rehmannia.
Nervine tonics, also simply referred to as nervines, are herbs which help to relax and energise the nervous system, by improving its tone, vigour, and function. Examples of nervine tonics include valerian, vervain, passionflower, skullcap, oatstraw, gotu kola.
Adaptogens
Siberian Ginseng is excellent in times of stress to support the nervous system, due to its adaptogenic action, meaning it helps to increase the body’s resilience to stress, particularly in cases of physical stress and fatigue. It can be helpful in cases of convalescence, debility, and as a tonic for the elderly (10), and tends to improve mental performance, concentration, physical performance, and exercise.
A recent study shared the results of USSR studies for the first-time in English, which were the first to investigate the physiological effects of Siberian ginseng during the 1960’s. The study revealed that over 1000 studies which included placebo controlled, and controlled trials were carried out, and indicated that Siberian ginseng exhibits benefits for cognitive function, and physical and mental endurance (11).
In addition to the adaptogenic actions Siberian ginseng is also immune modulating, meaning that it provides support for the immune system, helping to regulate healthy immune responses, which can also be affected with prolonged or intense stress.
Although generally considered gentle and supportive for the nervous system, for people who are particularly sensitive it can at times feel overly-stimulating, so this is worth bearing in mind when trying this herb.
Ashwagandha is an excellent tonic for the nervous system also helping to reset and balance stress responses. The unique qualities of ashwagandha mean that whilst it is known as an adaptogen, therefore increasing resilience to stress and energy levels, it is also deeply restorative.
Ashwagandha restores energy is on a very deep level, which can be thought of as laying a foundation for a healthy nervous system. This can be particularly helpful in cases of frazzled nerves when stress overwhelms and may be accompanied by a feeling of being tired and wired, which causes disturbances to sleep (either onset or waking during the night), or when one generally feels overly stressed and worn out from this.
Ashwagandha has gained attention recently becoming popular as many people hear about the benefits of adaptogens. Whilst it is wonderful that the benefits of herbs are becoming known to a wider audience, it may be noted that not all herbs are suitable for everyone all the time. Ashwagandha is a good example of these nuances of how herbs work for different people at different times.
For people who are extremely low on energy because of stress and nervous system tension, ashwagandha can temporarily make them feel more tired, due to its calming effect on the nervous system. Paradoxically, for some people ashwagandha can feel slightly stimulating, because of its deeply restorative effect which may give a sense of more energy, which might be too much for people who are already feeling tired and wired. In these cases, exploring the time of day the herb is taken can help, for example for those who feel sleepy when taking it try taking it in the evening, and for those who feel stimulated by it try taking it in the morning. Many people may not notice either of these effects and find that it feels supportive and subtly restorative over time.
Traditionally, ashwagandha is renowned in ayurveda for helping people who are experiencing overwork, lack of sleep, or nervous exhaustion (12).
Ashwagandha has a distinct smell which is thought to be reminiscent of horses, and traditionally it is said to give the strength and sexual vigour of a horse, so may be helpful in cases of stress or nervous exhaustion which affect libido.
Rhodiola is a wonderful adaptogen which helps to increase the body’s resilience to stress. It improves physical and mental performance, concentration, and memory, particularly when stress is affecting performance. Interestingly this plant can survive in high altitudes and low temperatures, and seems to improve our ability to withstand such conditions.
This plant has a long traditional history being renowned for enhancing physical and mental endurance, and for longevity. It is said that Chinese emperors looking for the secret to long life would send expeditions to search for this herb, and it was apparently popular with the Vikings for improving endurance (13).
In Russia, rhodiola has been an accepted medicine in the pharmacopoeia since 1969 where it is listed as a nervous system tonic, adaptogen, and antidepressant.
A double-blind placebo-controlled crossover trial was carried out on 60 individuals experiencing stress-related chronic fatigue. The trial measured quality of life, symptoms of fatigue, depression, attention, and saliva-cortisol response to awakening on days 1 and 28 of treatment. Both groups had positive results (due to possible placebo effect in the control group), however there were significant improvements in the treatment group compared with the control group relating to reduction of fatigue, improvements in mental performance, and ability to concentrate. Additionally, the post-treatment group cortisol responses to awakening stress were significantly different compared with the control group, suggesting that the herb is directly affecting the HPA axis stress response of the body. The authors concluded that taking the rhodiola extract has an anti-fatigue effect, enhancing mental function, and reduces cortisol response to awakening stress in burnout patients with fatigue (14).
Rhodiola is energetically cooling, meaning that it tends not to be overly stimulating as can be the case with some adaptogens. Its benefits for the nervous system include enhancing alertness, reducing fatigue, and improving memory (13).
Caution must be taken in ensuring the correct species of rhodiola is taken, since there are many species of which around 20 are used medicinally, and sometimes substitutions are made. Rhodiola rosea is the species which has been most researched for its beneficial effect on the nervous system.
Adrenal restorative
Liquorice is a fantastic herb for supporting nervous system health due to its impact on the body’s responses to stress. It is an adaptogen so it increases the body’s resilience to stress, whilst also being an adrenal tonic. Adrenal tonics improve the tone and function of the adrenal gland (15), and are therefore helpful in cases of prolonged stress, feeling overwhelmed, burnt-out, or fatigued from stress, by improving the function of the adrenal glands.
Adrenal tonics are particularly useful after prolonged periods of stress. Licorice benefits the function of the HPA axis helping to relieve symptoms of adrenal insufficiency such as fatigue, tiredness on waking in the morning, elevated cortisol and blood sugar levels (13). Licorice is also anti-inflammatory, which may reduce stress-related inflammation in the body.
Relaxing restorative nervines
Oatstraw is a nervous system tonic and trophorestorative like no other. It can be thought of as a nutritive medicine for the nervous system, helping to build it back up to health after long periods of stress, and when resting or sleeping do not do the trick. Particularly beneficial in cases of fatigue, and nervous exhaustion, it is mineral rich so acts a tonic and restorative for the whole body as well as the nervous system and can help to feel that it builds back up whilst convalescing, particularly from stress-related fatigue.
A randomised, double-blind, placebo-controlled study was carried out over 4 weeks to observe the effects of a green oat extract on cognitive function and responses to stressors in 132 healthy volunteers. Participants were given doses of the extract daily and tested at weekly intervals from the first dose. The results showed that after a single dose, and increasingly so with 4 weeks of the doses that performance of multitasking and memory tasks were significantly improved compared to placebo. After 4 weeks of the highest dose there was also a decreased physiological response to a stressor. The authors concluded that this study confirms the acute cognitive effects of Avena sativa extracts, and that longer-term supplementation can benefit cognitive function and modulate the physiological response to a stressor (16).
Valerian is helpful at relaxing and strengthening the nervous system, being restorative and calming (in most cases). Valerian is known as a nervine, which acts as a nervous system tonic and restorative, meaning that it helps to nourish, tone, and restore the tissues of the nervous system, allowing them to function better.
Valerian is particularly helpful in cases of insomnia, due to its sedative action, and because of its restorative effect on the nervous system it allows a deeper level of sleep to be accessed over time, meaning that the benefits of good quality sleep are also received, which do wonders for nervous system health.
In moderate doses valerian will be more restorative for the nervous system, rather than overly sedative, so it can still be taken during the daytime when nervous system support is required where it is beneficial in cases of stress or nervousness.
The Latin name for valerian valere means “to be strong, powerful, healthy”, suggesting that although this herb is restorative and relaxing for the nervous system, for some people it can feel stimulating, probably due to the increase in vital energy that it provides.
Vervain is a tonic for the nervous system which tends to relax the body and bring a sense of energetic grounding. This grounding effect can be helpful for supporting good quality deep sleep which can be beneficial when stress or a frazzled feeling nervous system results in disturbed sleep.
Because of the tonic effect on the nervous system vervain is beneficial in cases of anxiety, especially when irritability it present (10).
Passionflower has wonderful nervine qualities, which helps to relax the body and mind quickly bringing a feeling of calm, and easing over-thinking. It can be taken long term as a general nervous system support and is especially helpful in cases of stress accompanied by anxiety, or sleep issues, and when there is a general over-excitability or irritability. Passionflower was traditionally given as a tea by Native Americans for its sedative and anxiolytic effects.
Skullcap is a nervous system tonic which restores the healthy function of the nervous system. It has relaxing nervine qualities, which can help to ease over-thinking. Skullcap is particularly beneficial when there are sleep issues are due to emotional stress, or when there is excitability, irritability, or anxiety.
Skullcap is also a muscle relaxant, which makes it helpful in cases of nervous tension or stress accompanied by tension headaches, tight shoulders or general muscle tension, as well as palpitations, neuralgia, muscle twitching and tremors.
Herbalists consider skullcap to have an affinity with the head (clear from the name skullcap). It is traditionally used to help one stop worrying about things that we cannot do anything about.
Gotu kola is a great tonic for helping to restore brain function and clearer thinking which may have been impacted due to stress.
According to Ayurveda gotu kola is classified as a rasayana. Rasayanas are rejuvenative tonics which are thought to penetrate and revitalize the psycho-physiological being (12). Gotu kola is helpful in cases of poor memory, anxiety, mental fatigue, and irritability (13).
Holistic solutions
Diet
Blood sugar levels are closely linked to stress responses, so keeping them in check with regular balanced meals can help with our responses to stress. When we feel stressed or tired we are more likely to let healthy eating habits slip, so getting on top of this can really help to readjust the balance.
Eating a balanced diet will help to keep blood sugar levels balanced, which supports healthy stress response, maintains energy levels, and provides vital nutrients for the nervous system to function at its best.
General guidelines:
- Plenty of wholefoods (wholegrains, vegetables and fruit, pulses and legumes, nuts and seeds)
- Enough protein (this is vital for most processed in the body, including repair and energy production). Things like meat, fish, eggs are ideal sources of protein.
- Minimise or cut out processed foods and refined carbohydrates (pre-packed / ready-made foods, foods with added white sugar)
B-vitamins are involved in many nervous system functions, and ensuring sufficient levels is important for a healthy nervous system. The main food sources of many b-vitamins are meat, fish, and dairy, so if following a vegan or vegetarian diet it may be beneficial to consider occasional b-vitamin supplementation.
Relaxation
This may sound obvious but many of us have lost the art of relaxation, feeling we need to be ‘doing something’ all the time.
Relaxation can be deeply healing. Consciously cultivating calm gives us a stronger foundation from which to navigate the inevitable stresses of life, helping to maintain balance of health and wellbeing despite these fluctuations in external stressors.
Yoga Nidra which is a form of guided relaxation referred to as ‘Yogic sleep’ and a beneficial form or relaxation for restoring the nervous system. Yoga Nidra is thought to access the space between the waking and sleeping world, and the conscious and subconscious mind. This provides a deep relaxation and helps to reset behaviours bringing more harmony into daily life. This can be particularly helpful in altering our subconscious responses to stress.
Nature
Contact with nature is a sure-fast way to reduce stress with many benefits for nervous system health (17). Daily nature time if possible!
Meditation
Breathing
The breath-rate can be altered by HPA axis stimulation. For example, when feeling stressed, in the sympathetic or “fight or flight” state, breathing becomes shallow and the breath often remains up in the chest.
The opposite can also be true, we can help to re-activate the parasympathetic (rest and digest) branch of the autonomic nervous system just by slowing our breath rate down so that the exhale becomes longer than the inhale.
Breathing deeper down into the belly rather than chests is also referred to as the Yogic breath and one of the simplest yet most effective breathing practices of Yoga, which supports the shift into a more relaxed state. There are many other techniques which can help to activate deeper belly breathing, such as 7:11 breathing, and also other pranayama practices from Yoga traditions including deep breathing, anulom vilom, and bhramari.
These can assist in slowing the breath rate down and re-setting the autonomic nervous system from sympathetic to parasympathetic.
Summary
If you feel overwhelmed by the choice of herbs to support your nervous system, or have been experiencing prolonged stress which you feel has taken its toll on your health, then the guidance of a herbalist may be beneficial in providing support and specially tailored options for restoring health to your nervous system and stress responses. See the where to find a herbalist page for more information.
Referencess
- Guillams TG & Edwards L. Chronic Stress and the HPA Axis: Clinical Assessment and Therapeutic Considerations. The Standard. 2010;9(2). https://www.pointinstitute.org/wp-content/uploads/2012/10/standard_v_9.2_hpa_axis.pdf.
- Salleh MR. Life event, stress and illness. Malays J Med Sci. 2008;15(4):9-18.
- Merck Manual Consumer Version. Nervous System. 2021. https://www.merckmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/autonomic-nervous-system-disorders/overview-of-the-autonomic-nervous-system. Accessed 12 July 2023.
- Rotenberg S, McGrath JJ. Inter-relation between autonomic and HPA axis activity in children and adolescents. Biol Psychol. 2016;117:16-25. doi:10.1016/j.biopsycho.2016.01.015.
- Hussain LS, Reddy V, Maani CV. Physiology, Noradrenergic Synapse. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK540977/.
- Spencer RL, Deak T. A users guide to HPA axis research. Physiology & Behavior. 2017;178(1):43-65. https://doi.org/10.1016/j.physbeh.2016.11.014.
- Herman JP, McKlveen JM, Ghosal S, et al. Regulation of the Hypothalamic-Pituitary-Adrenocortical Stress Response. Compr Physiol. 2016;6(2):603-621. doi:10.1002/cphy.c150015.
- Patel D. HPA Axis Dysfunction Explained: The Facts You Need to Know. Functional Medicine. https://webfmd.com/hpa-axis-dysfunction/. Published 2019. Accessed October 09, 2022.
- Fulford AJ & Harbuz MS. An introduction to the HPA axis. Techniques in the Behavioral and Neural Sciences. 2005;15(1);43-65. https://doi.org/10.1016/S0921-0709(05)80006-9.
- Bone, K, The Ultimate Herbal Compendium. Warwick, Queensland: Phytotherapy Press; 2007.
- Gerontakos S, Taylor A, Avdeeva AY, et al. Findings of Russian literature on the clinical application of Eleutherococcus senticosus (Rupr. & Maxim.): A narrative review. J Ethnopharmacol. 2021;278:114274. doi:10.1016/j.jep.2021.114274.
- Frawley D, Lad V. The Yoga of Herbs. 2nd ed. Twin Lakes: Lotus Light Publications; 2008.
- Winston D, Maimes S. Adaptogens, Herbs for strength, Stamina, and Stress Relief. Rochester, Vermont.: Healing Arts Press; 2007.
- Olsson EM, von Schéele B, Panossian AG. A randomised, double-blind, placebo-controlled, parallel-group study of the standardised extract shr-5 of the roots of Rhodiola rosea in the treatment of subjects with stress-related fatigue. Planta Med. 2009;75(2):105-112. doi:10.1055/s-0028-1088346.
- Bone K, Mills S. Principles And Practice Of Phytotherapy. China: Churchill Livingstone Elsevier; 2000.
- Kennedy DO, Bonnländer B, Lang SC, et al. Acute and Chronic Effects of Green Oat (Avena sativa) Extract on Cognitive Function and Mood during a Laboratory Stressor in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled Study in Healthy Humans. Nutrients. 2020;12(6):1598. Published 2020 May 29. doi:10.3390/nu12061598.
- Hunter MC, Gillespie BW, Yu-Pu SC. Urban Nature Experiences Reduce Stress in the Context of Daily Life Based on Salivary Biomarkers. Frontiers in Psychology 10;2019. DOI=10.3389/fpsyg.2019.00722.
