endocrine-system

Quick Sheet: Hormones Produced in the endocrine system

Gland

    • Hormone(s) Produced
      • Primary Function(s)

Hypothalamus

    • Regulatory hormones
      • Control release of hormones from anterior pituitary

Hypothalamus (released from posterior pituitary)

  • Antidiuretic hormone (ADH)
    • Stimulates both the kidneys to decrease urine output and thirst center to increase fluid intake when the body is dehydrated; in high doses, ADH is a vasoconstrictor (thus, it is also called vasopressin)
  • Oxytocin
    • Contraction of smooth muscle of uterus; ejection of milk; increases feelings of emotional bonding between individuals

Pituitary gland (anterior)

  • Thyroid-stimulating hormone
      • Stimulates thyroid gland to release thyroid hormone
  • Prolactin (PRL)
      • Regulates mammary gland growth and breast milk production in females; may increase secretion of testosterone in males
  • Follicle-stimulating hormone (FSH)
      • Controls development of both oocyte and ovarian follicle (spherical structure that houses an oocyte) within ovaries; controls development of sperm within testes
  • Luteinizing hormone (LH)
      • Induces ovulation of secondary oocyte from the ovarian follicle
      • Controls testosterone synthesis within testes
  • Adrenocorticotropic hormone (ACTH)
      • Stimulates adrenal cortex to release corticosteroids (e.g., cortisol)
  • Growth hormone (GH)
    • Release of insulin-like growth factors (IGFs) from liver; GH and IGFs function synergistically to induce growth

Pineal gland

  • Melatonin
    • Helps regulate the body’s circadian rhythms (biological clock); functions in sexual maturation

Thyroid gland

  • Thyroid hormones:
  • T3 (triiodothyronine) and
  • T4 (tetraiodothyronine or thyroxine)
    • Increase metabolic rate of all cells; increase heat production (calorigenic effect)
  • Calcitonin
    • Decreases blood calcium levels; most significant in children

Parathyroid glands

  • Parathyroid hormone (PTH)
    • Increases blood calcium levels by stimulating both release of calcium from bone tissue and decrease loss of calcium in urine; causes formation of calcitriol hormone (a hormone that increases calcium absorption from small intestine)

Thymus

  • Thymosin, thymulin, thymopoietin
    • Maturation of T-lymphocytes (a type of white blood cell or leukocyte)

Adrenal cortex

  • Mineralocorticoids (e.g., aldosterone)
    • Regulate blood Na+ and K+ levels by decreasing the Na+ and increasing the K+ excreted in urine
  • Glucocorticoids (e.g., cortisol)
    • Participate in the stress response; increase nutrients (e.g., glucose) that are available in the blood
  • Gonadocorticoids (e.g., dehydroepiandrosterone [DHEA])
    • Stimulate maturation and functioning of reproductive system

Adrenal medulla

  • Epinephrine (EPI) and norepinephrine (NE)
    • Prolong effects of the sympathetic division of the autonomic nervous system

Pancreas

  • Insulin
    • Decreases blood glucose levels
  • Glucagon
    • Increases blood glucose levels

Testes (gonads)

  • Testosterone
    • Stimulates maturation and function of male reproductive system
  • Inhibin
    • Inhibits release of follicle-stimulating hormone (FSH) from anterior pituitary

Ovaries (gonads)

  • Estrogen and progesterone
    • Stimulates maturation and function of female reproductive system
  • Inhibin
    • Inhibits release of follicle-stimulating hormone (FSH) from anterior pituitary

Heart

  • Atrial natriuretic peptide (ANP)
    • Functions primarily to decrease blood pressure by stimulating both the kidneys to increase urine output and the blood vessels to dilate

Kidneys

  • Erythropoietin (EPO)
    • Increases production of red blood cells (erythrocytes)

Liver

  • Angiotensinogen
    • Converted by enzymes released from the kidney and within the inner lining of blood vessels to angiotensin II; increases blood pressure by causing vasoconstriction and decreasing urine output; stimulates thirst center
  • Insulin-like growth factors (IGFs)
    • Functions synergistically with growth hormone to regulate growth
  • Erythropoietin (EPO)
    • Increases production of red blood cells (erythrocytes); note that kidneys are the major producers of EPO

Stomach

  • Gastrin
    • Facilitates digestion within stomach

Small intestine

  • Secretin
    • Regulates digestion within small intestine by helping to maintain normal pH within small intestine
  • Cholecystokinin (CCK)
    • Regulates digestion within small intestine by facilitating digestion of nutrients within small intestine

Skin

  • Vitamin D3
    • Converted by enzymes of liver and kidney to calcitriol; functions synergistically with PTH and increases calcium absorption from small intestine

Adipose connective tissue

  • Leptin
    • Helps regulate food intake

Placenta

  • Estrogen and progesterone
    • Stimulates development of fetus; stimulates physical changes within mother associated with pregnancy including those in the uterus and mammary glands
Hormone Chart because I love you guys

Preliminary information:  The pituitary is secretly 2 things, the Adenohypophysis and the Neurohypophysis. The Adenohypophysis is NOT directly connected to the hypothalamus however it does receive hormones via the hypophyseal portal system (it’s a bunch of capillaries). The Adenohypophysis is also known as the ANTERIOR BODY of the pituitary gland.  The Neurohypophysis IS directly connected to the hypothalamus via the infundibulum and isn’t actually a true gland.  It makes ZERO hormones, and is mostly made of nerves.  All the hormones it sends out are actually made by the hypothalamus.  It is also known as the POSTERIOR BODY of the pituitary gland.  COOL STUFF BRO.  You all should know by now that the hypothalamus makes up the walls and floor of the 3rd ventricle in the brain (assuming you guiz are in A&PI or II, and not a casual reader).

GOING TOP DOWN

Dopamine when it’s not doing it’s business in our brain and affecting how we feel and perceive things emotionally and is circulating around our body is also PROLACTIN-INHIBITING HORMONE.  It’s made in the hypothalamus and inhibits the secretion of prolactin.  This means it affects the adenohypophysis.

There are a series of other inhibiting or releasing hormones made by the hypothalamus, but it isn’t super key in API or II and it IS key to know that PRL Inhibiting hormone is also dopamine. 

Antidieuretic Hormone (ADH) is made in the hypothalamus and sent to the neurohypophysis.  Its target organ is the kidneys and its effect is water conservation.

Oxytocin is made in the hypothalamus and sent to the neurohypophysis.  Its target organs are the mammary glands, uterus and the gonads.  Its primary effect is contractions, orgasms.  It also does bonding but that’s getting into neuropsychology and we’re not doing that here yo.

Adrenocorticotropic hormone is made in the adenohypophysis and its target organ is the adrenal cortex.  Its primary effect is adrenal cortex hormone production and release.

Follicle Stimulating hormone is made in the adenohypophysis and its target organ is the gonads.  Its primary effects are gamete production and testosterone production/release.

Growth Hormone is made in the adenohypophysis and its target organ is EVERYTHING, though primarily bones, at the epipheseal plates. It does growth.

Lutenizing hormone is made in the adenohypophysis and its target organ is the gonads.  It works with FSH to do ovulation, corpus lutenum maintenance, testosterone and androgen production.

Prolactin is made in the adenohypophysis and its target organ is the mammary glands.  It does lactation.

Parathyroid hormone is from the parathyroids and its target organ is bone.  It releases calcium ions in cases of hypocalcemia. 

Triiodothyronine (T3) is made in the thyroid follicular cells and it’s target organs are the cardiovascular system, the respiratory system, the nervous system and the digestive/excretory systems.  It raises metabolism/ “Calorigenic effect”

Tetraiodothyronine (T4) is the same as T3, except it is the less active hormone.  It’s the “travel” hormone and gets activated into T3 in different places.

Calcitonin is made in the thyroid’s C-cells and its target organ is bone.  It deposits calcium in cases of hypercalcemia.

Epinephrine is made in the Adrenal Medulla and it’s target organ is EVERYTHING, IT’S ALSO A NEUROCHEMICAL. Its effect is sympathetic responses.

Mineralocorticoids are made in the Zona Glomerulosa of the adrenal cortex.  Mineralocorticoids affect ion retention.  An example is Aldosterone, which conserves Sodium ions.  Its target organ is the kidneys.

Glucocorticoids are made in the Zona Fasiculata of the adrenal cortex and their target organs are muscle tissue and adipose tissue.  An example is cortisol which does glucose metabolism. 

Renin is made in the kidneys and it affects the kidneys and it is the first step in getting angiotensin to eventually be angiotensin II (it first converts angiotensin to angiotensin I).  In the long term it raises blood pressure.

Erythropoietin is made in the kidneys and liver and it affects red bone marrow.  Its effect is red blood cell production.

Calcitrol is made in the kidneys and it affects the small intestine.  Its effect is calcium ion absorption from diet.

Insulin is made in beta cells in islets in the pancreas.  It affects adipose tissue and muscle tissue.  It’s effect is that it encourages glucose deposits into muscle and adipose tissue.

Glucagon is made in alpha cells in islets in the pancreas.  It affects adipose tissue and muscle tissue.  Its effect is that it encourages glucose release from muscle and adipose tissue.

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Exocrine system enzymes! It’s important to know the difference between exocrine and endocrine glands for the 2015 MCAT!

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The Pineal Gland & The Endocrine System by Manly P. Hall

17/05/16, 23:49
24.5 hours later, 6 units later, 26 pages of review later, and a more thorough understanding now then when we originally learned it later, I am done. Tomorrow is the pay off.

About the Cardiovascular and Lymphatic and Endocrine and Respiratory System

Here’s how easy these systems were:

I didn’t make flashcards for ANY OF THEM.  I used my textbook, traced the arteries and veins for Cardiovascular.  Fetal circulation was a thing we had to learn and it SEEMED tricky but honestly it wasn’t a big a deal once I sat down with my book and read a little on how it worked and how it changed into “adult” circulation after birth.  It was super simple. For Lymphatic I just said “Cisterna Chyli” over and over because that was literally the only thing I was not certain I’d remember.Everything else was really easy to learn because there were things like “Thoracic Duct” which was a big ol’ lymphatic duct in the THORACIC CAVITY HOW EASY IS THAT.  Or Axillary or Mamillary nodes, which hang out in your armpit or breast/chest region respectively. The Spleen counted for lymphatic, and honestly it’s main job is to explode old RBCs and also foreign/diseased cell/matter so also: NBD

The Endocrine system is also easy because the Hypothalmus and Pituitary gland were the only things in the Brain unit (that I failed miserably) that I learned properly so I was all set up for Endocrine to learn those right.  With the adrenal glands I had a mnemonic “JAFAR: (G-F-R) to remember the order of the Zona Glomerulosa, Zona Fasiculata and the Zona Reticularis in the adrenal cortex. That’s superficial to deep, btw.  The medulla is easy. Most of it was remembering hormones and where they come from and what they do.   The different steroids of the Adrenals were a little tricky but mostly is was a no-duh sort of thing.  There was the thyroid which was easy (lobes and isthmus!) and the parathyroids (also easy) and thymus (easy!) and also the gonads and a little bit of pancreas and kidney.  Get your Islets v Acini straight and remember Insulin is from beta cells and Glucagon is from alpha cells and you’re golden on the pancreas.  Kidneys was all about the angiotensin II process so NBD.  Angiotensin I is made in the kidneys, moseys over to the lungs to get activated as Angiotenin II and then goes back to affect the kidneys.  It’s all about H2O conservation up in here!

PRO-TIP, THOUGH. While the respiratory system is also ridiculously easy to learn, PAY ATTENTION TO THE STRUCTURE OF THE ALVEOLI.  I didn’t pay attention enough and for questions involving the Alveoli (or actually, the names of the bronchi after the first two) I didn’t grasp.  Spent too much time making sure I could spell "Nasopharyngeal” correctly.  

My second practical involved everything except cardiovascular circulation, that was my first practical (88%) and I’m pretty confident I passed.  I’m not sure how well because I really dicked up with respiratory system, but everything else was perfectly studied for, IMHO.

Nervous System vs. Endocrine System.

MODE OF TRANSMISSION:

  • Nervous System: Fast
  • Endocrine System: Slow

RESPONSE DURATION:

  • Nervous System: Short term
  • Endocrine System: Long term

SPECIFICITY: 

  • Nervous System: Specific. (One neuron –> next neuron)
  • Endocrine System: General

NATURE OF INFO TRANSMITTED:

  • Nervous System: Electrochemical
  • Endocrine System: Chemical

TRANSPORT OF MESSAGE:

  • Nervous System: Neurons
  • Endocrine System: Bloodstream
Hormones

ADH - increases water re-absorption by the kidneys, decreases sweating (in large amounts causes vasoconstriction)

Result of ADH; decreases urinary output and increases BV and BP
Stimulus of ADH; nerve impulses from hypothalamus when body water decreases

Oxytocin - stimulates contraction of myometrium of uterus during labor and release of milk from mammary glands

Stimulus of Oxytocin; never impulses from hypothalamus as cervix is stretched or as infant suckles on nipple

Anterior Pituitary/Adenohypophysis - secretions are regulated by releasing hormones from the hypothalamus

  • GH - through intermediary molecules, IGFs, Gh increases amino acid transport into cells and increase protein synthesis, increases rate of mitosis, increases use of fats for energy
  • Stimulus; GHRH from hypothalamus
  • TSH (thyrotropin) - increases secretion of thyroxine and T3 by the thyroid
  • Stimulus; TRH from hypothalamus
  • ACTH (adrenocorticotropin) - increases secretion of cortisol by the adrenal cortex
  • Stimulus; CRH from the hypothalamus
  • Prolactin - initiates and maintains milk production by the mammary glands
  • Stimulus; PRH from hypothalamus
  • FSH (follicle-stimulating hormone) - in women; initiates development of ova in ovarian follicles and secretion of estrogen by follicle cells - in men; initiates sperm development in the testes
  • Stimulus; GnRH from the hypothalamus
  • LH (Lutropin)- In women; stimulates ovulation, transforms mature follicle into corpus luteum and stimulates secretion of progesterone - in men; stimulates secretion of testosterone by the testes
  • Stimulus; GnRH from the hypothalamus
  • Corpus Luteum is a temporary endocrine structure in mammals, involved in production of relatively high levels of progesterone and moderate levels of estradiol and inhibin A.

to be continued….it’s official…I hate learning the endocrine system.

I hate asking for things. I hate needing things and not being able to get them. I hate wanting to go out but wanting to stay inside. Explaining to people why I’m tired all the time is exhausting. Pride and social anxiety will be the death of me. This is probably just my thyroid talking. It does this thing where the levels get all wacked up in there and attacks your body just because. illnesses that you can’t see, can’t feel, can’t touch, can’t taste are the ones nobody cares about.

The Endocrine System and Testosterone, An Introduction

Testosterone is a steroid hormone seen in mammals, reptiles, birds, and other vertebrates and is one of the most highly conserved molecules in multicellular organisms. This will be an introduction to the chemistry, biology and mechanics of testosterone, a molecule that we’re almost all familiar with, yet don’t quite understand.

Starting broadly, let’s tackle the properties and important information about hormones and the endocrine system in general. The endocrine system is a lot like the nervous system and they both are the body’s two major communication systems. Unlike the nervous system where communication is rapid over short distances (think synapses), the signals sent by the endocrine system may have much longer delays, last for a much longer period of time, and travel much greater distances. While they both use chemicals as their messengers, the endocrine system utilizes the bloodstream as its highway while the nervous system does not (for the most part). 

The endocrine system consists of glands that secrete hormones that enter the blood and are carried to the target cells upon which they act. Different hormones have different target cells and one cell may secrete several different types of hormones! Overall, the endocrine system is a major player in your body’s control systems of metabolism and homeostasis.

Onto Hormones!

Steroid hormones are lipid based molecules made mostly of carbon and hydrogen making them nonpolar and have a very low solubility in water (ever wonder why your injectible testosterone is suspended in oil?). Steroid hormones are produced primarily by the adrenal cortex of the kidneys and your reproductive organs (ovaries and testes). In addition to testosterone, cortisol, aldosterone, cholesterol, and estradiol are steroid hormones as well.

All steroid hormones are derived from cholesterol. Cholesterol is stored inside the cell and once the cell is stimulated the free cholesterol is transformed by a myriad of chemical processes in several organelles into different hormones. Therefore steroid hormones and testosterone are made on demand. Once the final product is formed it diffuses (passively - remember the lipid bilayer and the fact that testosterone is a lipid based hormone? Yeah…) across the cell membrane and into the interstitial fluid and later into circulation. Again mentioning the lipid nature of testosterone it is not highly soluble in blood and thus is largely transported in the plasma bound to carrier proteins. *Something to note* Following the release into the blood steroid hormones may undergo further modification - testosterone can be converted into estradiol and vice versa. Thus, the major male and female sex hormones are not unique to males and females however the concentrations of the hormones vary substantially between the two.

Because hormones are transported by the blood they can reach virtually all tissues, which is what we mean when we say that testosterone acts “systemically”. The response to hormones, however, is very specific and involves only the target cells for that hormone. The ability to respond depends on the specific receptor for those hormones, in this case testosterone, on or in the target cell. Testosterone receptors happen to be within the cell and the binding of the hormone to a receptor leads to the activation (or in some cases the inhibition) of the transcription of certain genes - causing a change in the synthesis rate of proteins coded for by those genes.

With hormones already being a sort of broadcast molecule with long-acting and long-distance capabilities - this particular mechanism of hormone action is long even by hormone standards. But as you have probably seen, the effects of steroid hormones and testosterone in particular are profound.

This process is much more complicated than described here, but we hope this diluted version of anatomy and physiology 101 is helpful to some!

Much of this information was adapted from “Human Physiology: The Mechanisms of Body Function” 11th edition by Widmaier, Raff & Strang.