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12.03 Adrenal Gland

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Overview

  1. Adrenal Gland
    1. Location: on top  of kidney
    2. Tissues/structure
      1. Inner = adrenal medulla
        1. Catecholamines
      2. Outer = adrenal cortex
        1. Adrenocorticosteroid hormones
          1. Mineralocorticoids
          2. Glucocorticoids
          3. Androgens

Nursing Points

General

  1. Adrenal medulla
    1. Location – internal aspect of gland
    2. Composition
      1. Specialized sympathetic neurons – chromaffin cells
        1. No axons and dendrites
    3. When stimulated, chromaffin cells secrete catecholamines
      1. Norepinephrine = neurotransmitter
      2. Epinephrine (aka Adrenaline)
      3. Effects (fight or flight response)
        1. Increased BP, HR, circulation to skeletal muscles, lung ventilation
        2. Inhibits less important functions (digestion/excretion)
        3. Hyperglycemic effect:
          1. Glycogenolysis, gluconeogenesis →  increase glucose in blood
          2. Inhibits insulin
            1. Ensures glucose to brain
            2. Decreased uptake of glucose
          3. Glucose-sparing
    4. Association w/ adrenal cortex
      1. Stress stimulates medullary cells to secrete catecholamines which stimulate the cortex to secrete corticosterone
  2. Adrenal cortex
    1. Location – around outside border of gland
    2. Secretions → steroid hormones (corticosteroids or corticoids)
      1. Mineralocorticoids
        1. Act on kidneys to control electrolyte balance
        2. Aldosterone
          1. Sodium retention
            1. Water follows
          2. Potassium excretion
      2. Glucocorticoids
        1. Cortisol, hydrocortisone
        2. Stimulate
          1. Fat & Protein breakdown
          2. Gluconeogenesis
          3. Release of fatty acids and glucose into blood
        3. Anti-inflammatory effect
        4. Long term secretion suppresses immune system
          1. See lesson on Cushing’s Syndrome
        5. Lack of secretion leads to fluid and electrolyte imbalances
          1. See lesson on Addison’s Disease
      3. Sex steroids
        1. Androgens – control aspects of male development and reproductive anatomy
          1. Male
            1. Dehydroepiandrosterone (DHEA)
              1. Naturally weak
              2. Converted to testosterone in other tissues
              3. This source is minor – testes make most of testosterone
          2. Female
            1. Adrenal androgens comprise 50% of androgen needs
          3. Both
            1. Stimulate development of pubic and axillary hair
            2. Apocrine scent glands at puberty
            3. Sustain libido

References:

Betts, J.G., et al. (2017). Anatomy and physiology. Houston, TX: OpenStax, Rice University. Retrieved from https://openstax.org/details/books/anatomy-and-physiology?Book%20details

Study Tools

Video Transcript

Alright we’re gonna talk about the adrenal gland. The adrenal glad is incredibly important to our body. It’s a very small gland that sits on top of either kidney that you probably don’t think about every day. But we’re gonna talk about it and help give you a better understanding of what it is, what it does, and why it really matters. The adrenal glad is this triangular-shaped gland sitting on top of either kidney. And it’s made up of two different elements. We have our adrenal medulla that’s in the center, this kinda horseshoe-shaped piece in the center. And then we have the adrenal cortex, which is the outer portion that surrounds the adrenal medulla. The adrenal medulla again is the inner layer. It’s responsible for excreting catecholamines, things like norepinephrine, epinephrine. And we’ll talk about that in just a second. The adrenal cortex, or the outer layer, is responsible for excreting mineralocorticoids, glucocorticoids, and androgens. So the adrenal medulla, again the adrenal medulla is the center layer, this horseshoe-shaped center layer of the adrenal glad. It’s made of the specialized sympathetic neurons called chromaffin cells. They don’t have any axons, they don’t have any dendrites. And what they do is when it’s stimulated, epinephrine and norepinephrine are released. Now you’ve probably heard of epinephrine and norepinephrine before. Norepinephrine is a neurotransmitter. Epinephrine, aka adrenaline, plays a role in this fight-or-flight response. So it’s gonna do things like increase our heart rate, increase our blood pressure. It’s going to shift circulation to the skeletal muscle, increase ventilation in the lungs, and it’s going to inhibit some of these quote unquote less important functions. Things like digestion and excretion. The whole purpose of this is to prepare our body for this fight-or-flight response, to get us ready to move. Stop all these things that don’t need to be going on for us to fight or for us to run, and those things would be digestion and excretion. Imagine you’re being chased by a lion. The last thing you want is to be going through the digestive process or the excretion process. You need your heart to be going faster, you need your blood pressure, you need your lungs going. And that’s what is really important in this fight-or-flight response, and epinephrine plays a huge role in that. It also creates this hyperglycemic effect through gluconeogenesis and glycogenolysis. Both of those kinda leading to increasing glucose in our blood. Now why would we want that? It’s going to inhibit insulin, increase glucose in our blood, all for the purpose of increasing the amount of glucose that can get to our brain. We want our brain to be able to function. It’s a massive consumer of glucose, and so we’re really trying to create more glucose, get it all up into the brain. Alright, now how is this associated with the adrenal cortex? So, stress stimulates this medullary cells to secrete all these catecholamines, epinephrine, norepinephrine. And this stimulates the cortex, the adrenal cortex, to release corticosterone. So with that, let’s get into what the adrenal cortex does. Again, the adrenal cortex is this outer layer of the adrenal gland. It’s main purpose is to excrete or release steroid hormones, corticosteroids and corticoids. Now, we have a couple of different kinds of these. We have mineralocorticoids, glucocorticoids, and androgens. Mineralocorticoids act on the kidneys to control electrolyte balance. So aldosterone, what it does is it leads to sodium retention. Now water follows sodium, and so we’re retaining sodium, we’re retaining H20, retaining water. At the same time, this leads to potassium excretion. Retain sodium, water follows sodium, potassium leaves. So that’s kinda the big role of aldosterone with electrolyte balance. Then we also have our glucocorticoids. We have cortisol and hydrocortisone. The main role of these is fat and protein breakdown. It also plays a role in gluconeogenesis which is the creation of glucose. And it has a huge anti-inflammatory effect. Now what you’re gonna see with this is long-term secretion of glucocorticoids, of cortisol and hydrocortisone, is going to lead to a suppression of our immune system. And now if we have this long-term suppression of our immune system, it can lead to something called Cushing’s syndrome. Now we have a whole lesson on that. I invite you to go watch that. Now the lack of secretion over long-term can lead to fluid and electrolyte imbalances. And it can also lead to Addison’s disease. Again we have a whole lesson on that, and I invite you to go watch that. Now we also have the sex steroids, called androgens. They play a role in reproductive anatomy. For males, it plays a role in DHEA which is naturally weak, but it’s converted to testosterone in other tissues. Now the testes are the main source of testosterone and make most of the testosterone in the male body. For females, the adrenal androgens comprise about 50% of all the female needs for androgen. For both male and females, it stimulates the development of secondary sex characteristics like pubic and axillary hair, and it plays a role in sustained libido. So let’s review some of the key points really quick. The… Adrenal glad sits on top of the kidneys. It’s this triangular-shaped gland with two pieces. You have your adrenal medulla in the middle. And you have your adrenal cortex as the outer layer. The adrenal medulla plays a role in catecholamine release, epinephrine, norepinephrine, that plays a role in fight-or-flight. And then we also have our adrenal cortex which plays a role in mineralocorticoids, glucocorticoids, and androgen release. We talked about how those play a role in the body. A big thing to keep in mind here is that the adrenal gland is a main source of our flight-or-fight response. It’s the result of this catecholamine release, again this norepinephrine and epinephrine release, that creates this fight-or-flight response. This is an incredibly important gland. I hope this helps make it a little bit more clear for you guys, and kinda get those key points. Now, like we always say here at NRSNG, go out and be your best self today. Happy nursing.

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