Dear Readers,
Let’s continue our explorative journey of the Endocrine Glands. Now, put on your scientific goggles and take a slide down from your lungs (Thymus glands) to the top of your kidneys, the location of our mighty Adrenal Glands.
In this article (3.5/n-Part 1), we will learn all about the Adrenal Glands, powerhouse of our Endocrine System.
In the next Article (3.5/n-Part 2), we will discuss the effects of Yoga on Adrenal Glands.
The TL;DR
The Adrenal Glands-walnut size, triangular shape glands that sit atop of kidneys are the powerhouse of endocrine system.
The Adrenal Glands are superstar multitaskers, they secrete several hormones which influence stress response, immune health, sleep patterns, and even mood and are essential for normal processing of everyday functions, ranging from metabolism, cardiovascular functions to the fight-or-flight response.
The hypothalamic-pituitary-adrenal axis, or HPA axis tightly controls the functions of stress response.
The stress response is divided into three stages-alarm, adaptation, exhaustion. Prolonged exposure to the stressor may result in exhaustion and finally death.
Let’s dive deeper….
1.1 Adrenal Glands
(According to Kundalini Yogis: Sacrum chakra or Svadhisthana chakra)
Adrenal Glands (also known as suprarenal glands- supra means “above” and renal is related to the kidneys), triangular shaped, walnut size glands which sits on top of both kidneys were first discovered by an Italian anatomist Bartolomeo Eustachio in 1564. He detailed the precise description of the fine structure of the kidney, without the aid of a microscope, but presumably with a magnifying lens, as illustrated by seven plates (see his original drawings from his work). Eustachio’s original description of adrenal glands still holds true today.
“Both kidneys are capped on the extremity towards the cava by a gland. Both are connected by a fold of the peritoneum in such a way that one, if he is not very attentive, does not really overlook them, as if they were not present. Their shape resembles that of the kidneys… sometimes one is bigger, sometimes another…” —Bartolomeo Eustachio in 16th century (translated by Lenard)
Later in 1855, Thomas Addison (not the famous inventor!) first described the essential role of the adrenal glands for human survival, and this essential role was one year later confirmed by Brown Séquard.
1.2 Anatomy and Hormones of Adrenal Glands
Anatomically adrenal glands have two parts:
The Adrenal Cortex (Outer part): It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing different hormones.
Zona glomerulosa: Produces aldosterone (Mineralcorticoid), which plays an important role in the long-term regulation of blood pressure by managing the balance of potassium and sodium levels in the body. Also maintains the right balance of water in the body.
Zona fasciculata: Produces cortisol (Glucocorticoid), helps to regulate metabolism, sugar levels, cardiovascular functions and blood pressure. It also produces corticosterone, works with cortisol to regulate immune response and suppress inflammatory reactions.
Zona reticularis: It produces small amounts of androgens, male and female sex hormones. However, their impact is overshadowed by hormones released by testes and ovaries. Also, produces DHEA, which is a critical component for mental clarity and cognition. During times of stress, production of this hormone decreases.
The Adrenal Medulla (Inner part): releases adrenaline (epinephrine) and noradrenaline (norepinephrine) after the sympathetic nervous system is stimulated, which occurs when you’re stressed.
Adrenaline: increases heart rate, helping in rapid blood flow to the muscles and brain for ‘fight-or-flight’. It also spikes your blood sugar level by helping convert glycogen (stored form go Glucose in Liver) to glucose in the liver.
Noradrenaline: causes the narrowing of blood vessels (vasoconstriction), which results in high blood pressure.
1.3 Regulation of Adrenal Glands Hormones
The hypothalamic-pituitary-adrenal axis, or HPA axis, is tightly regulated chemical communication system between the hypothalamus, pituitary gland, and adrenal glands.
When body perceive something as stressful, stressor response is activated in Hypothalamus (located in the brain) which sends signal (via corticotropin releasing factor) to anterior Pituitary Gland (located in the Brain, called the Master Gland), which communicates (via adrenocorticotropic hormone) with adrenal glands. This message says “secrete cortisol”. Cortisol rapidly initiates the stress-coping strategy by communicating with heart, muscles, blood vessels, etc. The primary goal of this response is to mobilise energy. Since it is needed for many biological functions it has receptors almost everywhere in the body, including the brain. When cortisol’s job is done it signals back to pituitary and hypothalamus to activate the shut-off process (negative feedback loop) till body faces another stressor.
Mother Nature is very efficient and minimises the amount of work done by any one biological system. Once job is done, it comes in homeostasis.
** Ever wondered, Why you have lots of energy when you wake up and Why you sometimes feel a little slow in the afternoon?
Well, this happens because of circadian rhythm of cortisol.
Cortisol released in times of stress (Reactive Cortisol) but we need a steady stream of cortisol in our blood to perform bodily functions (Resting or Basal Cortisol).
1.4 The Stress Reaction: What happens in our Body when we are Stressed!?
Hans Selye, father of stress research, borrowed the term stress from the field of physics in 1936. He defined stress as “the non-specific response of the body to any demand for change”. He proposed the General Adaptation Syndrome (GAS), which consisted of three phases: alarm, adaptation, exhaustion.
Stressors can be objective stressors that are universal (i.e., pandemic, earthquakes, tsunami, etc) or subjective stressors that cause different reactions in different people (i.e., time pressure at work, traffic, paying taxes, writing an exam).
In general terms, stress is a pattern of physiological, behavioural, emotional, and cognitive responses to real or imagined stimuli that are perceived as preventing a goal or endangering or otherwise threatening well-being—Martin, 2013
Our hard-wired stress response is designed to give us the quick burst of heightened alertness and energy needed to perform our best. But stress isn’t all good. When activated too long or too often, stress can damage virtually every part of our body. Prolonged exposure to the stressor may result in exhaustion and finally death. Watch this video to understand the long-term effects of stress on our body.
Here are some of the changes that occur during the stress response :
Energy is transformed and created
Blood sugar level spikes by helping convert glycogen (stored form go Glucose in Liver) to glucose in the liver.Cardiovascular activities pump into action
Your heart rate increases to pump more blood into our muscles.
Your arteries constrict to increase blood pressure.
Your veins open up to ease the return of blood to the heart.Inhalation/Exhalation increases to help the respiratory system.
Senses sharpen and toughen to keep you alert.
Your pupils dilate (enlarge) so you can see more clearly.
Your hairs stand up, making you more sensitive to touch.
You secrete endorphins, our natural pain killers that numb pain in the case of injury helping to stay you focused.Digestion and elimination stops.
Skin changes occur.
Blood vessels constrict reducing blood loss in case of injury.
Sweat glands open up to cool you down.Reproduction stops.
1.5 Adrenal Glands Dysfunctions
There are multiple reasons (infections, tumors, genetic disorders and autoimmune diseases, or as a side effect of medical therapy) responsible for malfunctioning of Adrenal Glands. Let’s look into some of the most common diseases:
Addison’s disease: develops when the adrenal cortex fails to produce enough cortisol and aldosterone.
Cushing’s syndrome: It is essentially the opposite of Addison’s disease, caused by overproduction of the hormone cortisol.
Adrenal cancer: Adrenal cancer is rare but an aggressive cancer, tumor cells tend to spread to other organs and cause adverse changes within the body because of the excess hormones they produce.
Congenital adrenal hyperplasia: Genetic disorder characterised by low levels of cortisol and additionally low levels of aldosterone (which maintains a balance of water and salt).
Symptoms of adrenal gland disorders may include: dizziness, excessive fatigue, sweating, nausea, vomiting, increased salt cravings, low blood sugar, low blood pressure, also known as hypotension, irregular periods, dark patches on your skin, muscle and joint pain, weight gain or loss.
** Do you Know? Stress can also play a crucial role in addiction when we try to mitigate it with comfort foods or stimulants.
If you found the article of interest or have thoughts about what you’ve read here, please do share in the comments section below. It will help guide my future posts.
In the next article (3.5/n - Part 2), I will cover the science behind the effects of Yoga on the Adrenal Glands. Until then, Stay healthy and happy :)
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