Emma Stewart Writes

Tag: medicine

  • Physical Effects of Mental Health: Neurotransmitters

    Physical Effects of Mental Health: Neurotransmitters

    There are many physical effects of our mental health. Neurotransmitters play a huge role in mental and cognitive functions. A lot of people separate mental and physical health issues, and mental health still carries a lot of stigma.

    Scientific background: image of a brain with text 'Mental health matters' then more text 'physical effects of mental health.'

    “It’s all in your head!”

    Except, that doesn’t make it any less real. Mental health problems are real, important and worthy of the same consideration. Neurotransmitters affect nearly all parts of the body in some fashion, which means that mental health issues do have physical effects.

    The full relationship is unclear, whether changes in brain chemistry cause the symptoms and behavioural changes. Or the symptoms and behavioural changes cause the changes in brain chemistry.

    Neurotransmitters are chemical messengers that cross the synapses and bind to receptors to send messages between the neurons and end organs. They either stimulate or inhibit depending on the receptor type. This subject is complex, so we’re going to fous on the important neurotransmitters that matter the most in mental health disorders.

    Serotonin

    A very important neurotransmitter, serotonin is known as 5-hydroxytryptamine or 5-HT. It is a monoamine neurotransmitter produced by the gastrointestinal tract. Enterochromaffin cells release serotonin, which is synthesised from tryptophan in dietary proteins.

    Serotonin regulates mood, cognition, reward, learning, memory and sleep. It also regulates the digestive system, including appetite, vomiting and other digestive processes. It also acts on the blood vessels to manage blood pressure.

    Excessive levels of serotonin result in serotonin syndrome, a serious and potentially life-threatening condition. Overdose or certain combinations of drugs put a patient at risk of serotonin syndrome. For example, combining an SSRI (Selective serotonin reuptake inhibitor) and an MAOI (Monoamine oxidase inhibitor) together. However, serotonin receptors make up important targets for all kinds of pharmaceuticals, including but not limited to mood disorders, anti-emetics (stop vomiting/nausea) and migraine treatments.

    Dopamine

    Known as the ‘pleasure chemical’, dopamine plays many roles in the body. It is a catecholamine neurotransmitter produced in the brain. There are many dopamine pathways, the most important and well known being the ‘reward-motivated behaviour’.

    Anticipation of a reward increases dopamine levels, as do pleasurable experiences. Dopamine plays a role in motor control and managing the release of a number of hormones. Addictive drugs affect dopamine levels and reinforce the cravings and addiction.

    Parkinson’s disease involves the loss of dopamine producing cells in the brain, causing the symptoms of the disease. Dopamine plays important roles in schizophrenia and ADHD as well.

    Dopamine acts as a stimulant to treat low blood pressure, slow heart rates and cardiac arrest, especially useful in newborns. Amphetamines increase dopamine levels in the brain, hence their use in treatment of ADHD, which improves quality of life for lots of people.

    Norepinephrine

    You may know this one as ‘noradrenaline’, both terms are correct but norepinephrine is the general international standard. It is a catecholamine with endocrine (hormone) functions as well. It plays a role in the ‘fight or flight’ response by increasing alertness, vigilance, enchancing memory functions and focusing attention.

    Adrenergic receptors respond to norepinephrine and are a common target for medications. Stimulants increase the amount of norepinephrine. Serotonin-norepinephrine reuptake inhibitors (SNRIs) and amphetamines fit into this category. Antagonistic drugs include beta-blockers which are prescribed to manage anxiety by reducing the heart-rate.

    Stress and anxiety, both acute and chronic, increase the levels of norepinephrine alongside other signalling molecules like epinephrine (adrenaline) and cortisol. Norepinephrine function may also play a role in ADHD. Lack of REM sleep increases norepinephrine secretion and leads to degeneration of the nervous system.

    GABA

    Gamma-aminobutyric acid, the chief inhibitory neurotransmitter in adult mammalian central nervous systems. Growing animals require it for brain development. The pancreatic beta-islet cells produce GABA to inhibit glucagon secretion.

    Many drugs target GABA receptors, including most commonly used anaesthetic drugs like propofol and barbiturates. GABA analogues like pregabalin and gabapentin have anti-convulsant effects and pain management functions.

    Glutamate

    Glutamic acid, an amino acid that humans can produce in the body. This means it’s not an essential amino acid. GABA synthesis uses glutamate as a precursor. It plays a role in learning and memory functions.

    Ketamine modulates glutamate and has proven beneficial in treating depression, especially treatment-resistant depression.

    Glutamate and its salts are a flavour enhancing compound, found in many foods. It gives an umami, or savoury, flavour in foods. A well-known example, monosodium glutamate (MSG) was unfairly maligned in the past.

    MSG naturally occurs in fermented or aged foods like soy sauce, fermented bean paste such as miso, and cheese. MSG is also an additive used in food production. The controversy around it is based in racism against East Asian people. You can eat it, it’s safe.

    Acetylcholine

    An important neurotransmitter, acetylcholine is an ester of acetic acid and choline, the body parts that it affects are called cholinergic. Acetylcholine activates the muscles via the motor neurons, as well as a vital role in the autonomic nervous system. Especially the parasympathetic nervous system.

    In the brain, it is involved in arousal, attention, memory and motivation. Toxins from plants, animals and bacteria act on cholinergic receptors to deactivate or hyperactivate them, causing paralysis.

    Atropine acts on muscarinic cholinergic receptors to treat heart and eye conditions, but excessive doses are toxic. Nicotine acts on nicotinic cholinergic receptors in the brain, which is why nicotine is so powerfully addictive.

    Myasthenia gravis is an autoimmune disorder where antibodies against the acetylcholine receptors cause muscle weakness and fatigue, which is often progressive. In addition, acetylcholine is involved in cognitive decline, Alzheimer’s disease and may also play a role in mood disorders, schizophrenia and ADHD.

    Conclusion

    This summary of neurotransmitters will help as we discuss common mental health disorders and the impact they have on the body. All of these chemical messengers facilitate physical and physiological effects on us.

    We need to discuss mental health more often, reduce the stigma around it and educate people. It’s important, yet often subject to misunderstanding and willful ignorance. Come back next week when we will discuss depression. Thanks for reading! Here’s a short summary of these neurotransmitters and their effects.

  • Blood Sugar Regulation Hormones

    Blood Sugar Regulation Hormones

    Image titled blood sugar regulation. Contains image of chemical formula of glucose, an insulin vial, a bag of sugar and a pair of hands using a glucometer.

    The body needs energy to function. This energy must be obtained from food, processed and metabolised so it is ready for the cells to use. Glucose, a sugar molecule, makes up the most important energy source. The brain alone uses 20% of the glucose produced by the body.

    Like many other factors, blood glucose must be maintained at the correct levels for everything to function as it should. Blood glucose and blood sugar are the same thing, so we’ll use ‘glucose’ going forward. The two main hormones oppose each other to maintain the balance of blood glucose.

    Important Definitions

    Glucose: a small sugar molecule the body uses for energy to function.

    Glycogen: a long branched molecule, made up of glucose molecules. It acts as storage of energy for later use, mainly in the liver and skeletal muscles.

    Glycogenolysis: the breakdown of glycogen into glucose.

    Glycogenesis: the creation of glycogen from glucose. Don’t mix these two up!

    Gluconeogenesis: the process of making glucose from non-carbohydrate sources such as fats and proteins.

    Hypoglycaemia: low blood glucose.

    Hyperglycaemia: high blood glucose. Don’t mix these two up, check your prefixes!

    Insulin: The Anabolic Hormone

    The hormone insulin controls anabolism: the storage and utilisation of energy. Insulin secretion takes place in the beta-cells of the islets of Langerhands, within the pancreas. It promotes glucose uptake from the blood into the body cells. It also promotes glycogenesis and fat generation, in other words, the storage of energy.

    High blood glucose levels stimulate insulin secretion by the pancreas, with the aim of reducing blood glucose to normal again. For this reason, insulin follows a cycle where it is released shortly after a meal to store away the energy from food.

    Most people have heard of diabetes mellitus, an endocrine disease involving insulin function. There are two main types of diabetes mellitus, which I am specifying because there is another kind of diabetes that is less well known, diabetes insipidus. So, let’s look at the details of diabetes mellitus.

    Type 1 Diabetes Mellitus

    An autoimmune condition, the immune system attacks the beta-cells in the pancreatic islets. Insulin production is halted or massively reduced, which is why T1 diabetics need to inject insulin regularly to manage their blood glucose. The result is excessively high blood glucose.

    Type 2 Diabetes Mellitus

    This form is much more complex and still not completely understood. Various risk factors contribute to reduction of beta-cells and insulin resistance. The cells don’t respond to insulin like they should and take up glucose from the blood. Increased glucagon secretion, unresponsive to blood glucose, could also be a factor.

    The end result is a persistent hyperglycaemia which results in the symptoms of diabetes. We’ll cover the details of this later.

    Glucagon: The Catabolic Hormone

    Glucagon opposes insulin, counteracting all of its effects. The alpha-cells of the pancreatic islets produce glucagon in response to low blood glucose. Glucagon raises blood glucose and fatty acids, stimulates glycogenolysis and gluconeogenesis. In other words, taking glucose out of storage and making more of it.

    Excessive glucagon levels contributes a lot to the development of hyperglycaemic ketoacidosis in undiagnosed or poorly managed type 1 diabetics. Ketoacidosis (DKA) becomes a diabetic coma if untreated and is life-threatening.

    The Effects of Hyperglycaemia

    An excessively high blood glucose impacts almost all of the body in some way. The main symptoms of diabetes mellitus include the triad of polyphagia, polydipsia and polyuria. Polyphagia means increased appetite or eating more than normal. Polydipsia means increased thirst or drinking more than normal. Polyuria means producing more urine than normal, referring to volume rather than frequency. That said, a higher volume of urine will typically increase the frequency of urination.

    Other symptoms include vision changes, fatigue, weight changes, poor wound healing, neuropathy (tingling in legs and feet), recurrent infections, coma and seizures.

    As mentioned before, ketoacidosis is a life-threatening complication of persistently high blood glucose levels. When the cells can’t use glucose, they produce ketone bodies to make energy from instead. These ketones make the blood more acidic and cause damage. Some people can smell the ketones, usually described as a ‘fruity’ smell or like nail polish. I personally can’t smell ketones very well.

    Other diseases cause hyperglycaemia including other endocrine disorders, sepsis and brain pathology. Certain medications also affect blood glucose, particularly certain steroids, beta-blockers, statins and antipsychotics.

    Stress impacts blood glucose, as the physiology of stress prepares the body for fight or flight, including making energy available. Stress induced hyperglycaemia matters a lot in cats, because they show extreme changes in blood glucose when stressed. For this reason, diagnosing diabetes mellitus in cats is not straightforward.

    Most cats are stressed simply visiting the vet, especially if a blood sample is taken, so one high glucose result in a cat means nothing. Further testing needs to be done to confirm a diagnosis of diabetes.

    The Effects of Hypoglycaemia

    Hypoglycaemia is more immediately life-threatening than hyperglycaemia. Symptoms of low blood sugar include headaches, confusion, light-headedness, heart palpitations, anxiety, nausea and tremors. Severely low blood sugar causes seizures, loss of consciousness and even death.

    The brain relies on glucose for energy, with no other option available to the cells. Hence the neurological symptoms and risk of seizures and brain damage.

    Excessive insulin causes hypoglycaemia, whether it is an accidental overdose, not eating after taking insulin, being injected with insulin when not diabetic or an insulinoma. Insulinomas are tumours of the pancreatic islet cells and while benign, they produce insulin in an uncontrolled way.

    Adrenal disease like Addison’s disease (hypoadrenocorticism), sepsis (glucose stores are used up) and other serious illnesses can cause low blood sugar too. Alcohol consumption, fasting and intense exercise, especially if diabetic will risk hypoglycaemia. Starvation, including eating disorders and neglect as well.

    Xylitol, the artificial sweetener, causes a rapid release of insulin in dogs. This results in hypoglycaemia and liver damage. Xylitol only affects dogs in this manner, but it is a common ingredient in gum, mints, peanut butter, medications, supplements, sunscreen, toiletries and cosmetics. Dog owners, beware because xylitol toxicity is an emergency and needs rapid treatment.

    Thanks for reading! April’s themes will be the physical impact of mental health problems on Mondays, and cats on Fridays for our Creature Features! Subscribe for updates when new posts are live. See you soon!

    Emma Stewart Writes

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  • The Stress Hormone: Cortisol

    The Stress Hormone: Cortisol

    The ‘stress hormone’ cortisol is extremely important for managing and regulating the body’s response to stress. Cortisol regulates metabolism, the response to stress and the immune system. The adrenal glands release cortisol, regulated by the hypothalamus and the pituitary gland in the brain.

    Adrenal Glands

    The paired adrenal glands live just above each kidney and are directly connected to part of the autonomic nervous system. The adrenal medulla produces adrenaline (epinephrine) and noradrenaline (norepinephrine), both of which play a role in the ‘fight or flight’ response. Read more about that system here.

    The adrenal cortex produces glucocorticoids, of which cortisol is the most important. The hypothalamus regulates cortisol secretion via the HPA axis, the hypothalamus—pituitary—adrenal cortex axis. A negative feedback loop maintains cortisol at an appropriate level.

    The hypothalamus releases CRH – corticotropin releasing hormone. This stimulates the anterior pituitary to secrete ACTH – adrenocorticotropic hormone. ACTH reaches the adrenal glands and causes cortisol secretion. Cortisol levels feed back into the hypothalamus and pituitary gland to reduce secretion of CRH and ACTH, keeping cortisol levels where they need to be.

    Role of the HPA Axis

    This system maintains homeostasis in the body by regulating metabolism, the cardiovascular system, immune system, reproductive system and the central nervous system. That’s a lot of jobs! Serious illness results from this system going wrong.

    Cortisol

    A glucocorticoid or ‘steroid’ hormone, cortisol is the stress hormone. It follows a diurnal cycle, increasing after waking, slowly dropping until late afternoon. It then resurges before dropping to its lowest point in the middle of the night.

    Pharmaceutical versions include hydrocortisone, prednisolone and several other ‘corticosteroids’. Applications include treating inflammation, managing autoimmune disorders, chemotherapy and treating allergies.

    The Effects of Cortisol

    Glucose Metabolism

    Cortisol stimulates glucose synthesis and the breakdown of glycogen in the muscles. It also increases the breakdown of fats and blocks insulin. It causes insulin resistance in an effort to increase blood glucose levels, i.e. blood sugar.

    Immune System

    Cortisol reduces the immune response, the inflammation cascade and reduces T-cell growth. That means it is immunosuppressive. This is why pharmaceutical steroids are used to treat immune-mediated and autoimmune diseases like rheumatoid arthritis, psoriasis, eczema and allergies.

    Cortisol delays wound healing, because it suppresses inflammation. The inflammation process plays a role in healing of wounds, whether injuries or surgical. Steroid treatment is withdrawn prior to surgery whenever possible, for this reason.

    Electrolytes and Water Homeostasis

    Cortisol increases GFR (glomerular filtration rate), in other words, function of the kidneys. It causes excretion of phosphate and potassium, along with water and sodium retention. Too much cortisol or not enough cortisol will cause electrolyte disturbances.

    Cortisol also stimulates secretion of stomach acid, which explains why chronic stress causes problems like heartburn and stomach ulcers. People who are stressed for a long time have high ciruclating cortisol levels.

    Memory

    Cortisol combined with adrenaline stimulates memories of short-term emotional evens in order to ensure we avoid the same thing in future. This effect is part of how trauma affects the mind and body in the long term. It is absolutely a factor in the development of PTSD.

    Long term exposure to excess cortisol damages the hippocampus, the part of the brain essential for storing long term memories and learning. This means excess cortisol impairs the ability to learn.

    Pregnancy

    During pregnancy, cortisol plays two essential roles. At 30-32 weeks gestation, cortisol stimulates production of pulmonary surfactant. Surfactant allows the lungs to expand when the first breaths are taken after birth. Without it, the newborn cannot breathe. One of the byproducts of beef production is extracting this surfactant from the cow’s lungs. Cattle lung surfactant massively improved survival rates of premature babies.

    The second role is to stimulate parturition, to initiate labour. Foetal cortisol triggers conversion of progesterone to oestrogen which in turn stimulates prostaglandin secretion and oxytocin receptor development. Oxytocin is the hormone that stimulates contractions of the uterus. Because it reduces progesterone, treatment with steroids can induce miscarriage in early pregnancies.

    Stress

    So why does this matter? The adrenal glands function to help the body cope with stressors. Adrenaline and sympathetic nervous system is there for acute dangers and cortisol is there for longer term stresses. If you are writing about someone who has been living a stressful life, they will have high levels of cortisol which impacts their physiology.

    Cortisol increases insulin resistance and thus contributes to potential risk factors for type 2 diabetes mellitus. Research into this is ongoing and while stress or high cortisol alone isn’t enough to cause diabetes, it could be part of the complex of risk factors.

    Cortisol affects the immune system and impacts immune-mediated disease. Interestingly, cortisol can both suppress the immune system and over-activate it. We know that stress impacts autoimmune diseases.

    The HPA axis is regulated by dopamine, serotonin and norepinephrine – neurotransmitters responsible for regulating mood and emotions. This connection shows how psychological stress impacts our physiology, and vice versa.

    Oxytocin down-regulates the HPA axis, reducing stress. Oxytocin is the ‘love hormone’, aside from its role in giving birth and milk let down in animals, it is released when we are close with people we love, including hugging and even during orgasm. So it proves that spending time with those we are close to can help reduce stress. This even applies to our pets!

    I talked previously about the term ‘psychosomatic’ discussed in the medical terminology series. Psychosomatic means that psychiatric changes, such as mental health disorders, have an impact on our physical bodies. It does not mean that your problems are ‘all in your head’ and not real. They are real, and mental distress has an impact on our physiology too.

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  • Endocrinology For Writers

    Endocrinology For Writers

    Endocrinology for writers is the new Monday blog series for March. Endocrinology is the study of the system of hormones and signals the body uses to manage its functions. It’s a complex subject and many people find it confusing. I’m here to help try to make it easier to understand.

    Why will this help writers? It allows you to understand important body functions such as responses during stress and fear, illnesses and conditions like diabetes and reproduction. Knowing what each of the important hormones actually do helps you understand and describe the effects and behaviours. So let’s get into it with some definitions.

    Endocrinology Definitions

    Hormone: signalling molecules secreted by endocrine glands to regulate physiology and behaviours. Hormones take different forms; amino acid complexes, steroids, eicosanoids, leukotrienes and prostaglandins.

    Glands: glands that produce and secrete hormones into the bloodstream. Some organs have endocrine functions as well as their other functions in the body.

    Neuroendocrine system: thepart of the brain that connects to the endocrine system and controls the release of hormones based on input from the nervous system.

    Axis: a sequences of endocrine glands that signal each other in a specific order to control hormone secretions.

    Homeostasis: the steady state of optimal physiological function. The endocrine system manages the body in order to maintain this.

    Tropic hormones: these hormones target other endocrine glands and organs to stimulate them to produce other hormones. The anterior pituitary gland secretes the majority of these hormones.

    Feedback loops: the endocrine system has negative feedback loops that control the production of hormones. For example, high levels of cortisol will cause the hypothalamus to stop producing hormones that stimulate cortisol production. This stops the body producing too much of a hormone.

    Endocrine Glands and Organs

    The endocrine system involves the entire body and many organs and glands are involved, both secreting hormones and responding to hormones. The neuroendocrine system is the part of the brain responsible for controlling hormone release.

    Neuroendocrine System

    Pineal gland: the pineal gland within the brain produces melatonin, a homrone derived from serotonin, which regulates the sleep cycle. The pineal gland links to a light sensing organ called the ‘parietal eye’ or ‘third eye’ in reptiles and amphibians. This is most notable in tuataras, a lizard-like reptile that is the last surviving species of its category.

    Hypothalamus: this part of the brain organises inputs from all other parts of the brain and responds by releasing hormones and tropic hormones. This triggers the pituitary gland.

    Pituitary Gland: there are three lobes of the pituitary gland:

    • Anterior: responds to tropic hormones and releases other hormones
    • Intermediate: only functional in the foetus
    • Posterior: direct nerve connection to hypothalamus and produces oxytocin and vasopressin (anti-diuretic hormone or ADH)

    This system controls all aspects of reproduction; bonding, sexual behaviour, spermatogenesis (sperm production), ovarian cycle, parturition (giving birth), lactation (milk production) and maternal behaviour.

    It also controls regulation of metabolism, eating and drinking, fat metabolism, mood regulation, fluid and electrolyte homeostasis and blood pressure.

    Glands

    Glands are organs that specifically produce hormones as their main function. You may know some of them already. So let’s get into the details.

    Thyroid gland: The thyroid gland is located just below the larynx and has two lobes. It secretes the thyroid hormones thyroxine (T4) and triiodothyronine (T3) to control metabolism.

    Parathyroid glands: Four tiny glands located behind the thyroid gland, hence the name. The parathyroid glands produce parathyroid hormone (big surprise!) an important hormone for calcium homeostasis.

    Adrenal Glands: a pair of glands located above the kidneys, split into two regions with different functions. We’ll cover this in detail in a later post.

    • Adrenal cortex: produces glucocorticoids, mineralocorticoids and androgens
    • Adrenal medulla: adrenaline (epinephrine) and noradrenalin (norepinephrine)
    • The adrenal glands also produce dopamine and enkephalin

    Gonads: the primary organs producing sex hormones and gametes. I’m including the uterus and placenta too.

    • Testes: the male gonads produce androgens such as testosterone, oestradiol (estradiol Am. Eng.) and inhibin.
    • Ovaries and Corpus Luteum: progesterones, oestrogens (estrogens Am. Eng.) and inhibin.
    • Placenta: progesterone, oestrogens, human chorionic gonadotrophin (hCG) and human placental lactogen.
    • Uterus: during pregnancy it produces prolactin, which stimulates milk production, and relaxin which affects blood flow and relaxes the pelvis and birth canal.

    Organs With Endocrine Functions

    Several organs have endocrine functions in addition to their other functions. Not only do they produce hormones, they also respond to hormones as well as other changes in the body’s physiology.

    Pancreas: the pancreas has exocrine functions (digestive enzymes) and endocrine functions related to blood glucose (blood sugar) and metabolism.

    • Insulin – produced in the β-islet cells (beta-islet) to reduce blood glucose and stimulate glucose uptake by cells.
    • Glucagon – produced in the α-islet cells (alpha-islet) to increase blood glucose and glucose production in the liver.
    • Somatostatin – produced in the δ-islet cells (delta-islet) to inhibit release of insulin and glucagon.

    Kidneys: the kidneys produce erythropoietin which stimulates production of red blood cells in the bone marrow. They also release renin, which is involved in the RAAS system and calcitrol, the active form of vitamin D3.

    Liver: produces insulin-like growth factor (IGF), thrombopoietin (THPO) to stimulate platelet production, hepcidin, angiotensinogen and angiotensin. The later two are also part of the RAAS system, which we’ll cover at a later date.

    Heart: ANP (atrial natruiretic peptide) and BNP (brain natruiretic peptide) released from the muscle cells of the heart control blood pressure.

    This covers a basic introduction to endocrinology for writers. Over the next few weeks we will cover the important systems that will help you understand how important endocrinology is for our behaviours and emotions. Don’t forget to subscribe for more updates and find me on my social media channels.

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