endocrine system

Multiple hormones can be made with one gland, or one hormone can be made by multiple glands

amine hormones

include thyroid hormones & catecholamines (epinephrine, dopamine , norepinephrine)

all thyriod hormons are derived from

tyrosine

thyroid hormones

hydrophobic, they don’t like being in the blood because it is a watery medium

catecholamines

a type of hormone that Includes epinephrine and norepinephrine and is secreted by the adrenal medulla ( the core of the adrenal gland )

• Made up of 80% epinephrine

• 20% of norepinephrine

• a little dopamine

dopamine is also

a hormone also secreted by your hypothalamus, making it an inhibitor for prolactin bc is secreted from the hypothalamus ( controlled by inhibition rather than exceleration )

Most hormones are polypeptides, making them

hydrophilic, making the soluble in the blood

hormones can be made

Of three to a hundred amino acids bound together by peptide bonds

• can also be made in advance, packed, stored in the cell, and released as needed

Pre-hormone

an inactive form of a hormone and must be converted to a pro- hormone

pro-hormone

an active form of a hormone, which will be packaged in the Golgi apparatus and be released by exocytosis

insulin

This hormone is also a polypeptide hormone. When the pre-hormone is processed into insulin, it also creates the C-peptide, but insulin is the main messenger

steroid hormones

• Derived from cholesterol

• Produced by our gonads and adrenal cortex

adrenal cortex

produces cortisol and aldosterone ( steroid hormones )

all steroid hormone are fatty making them

unable to be stored in the cell, instead, they are made on demand in the cell

• Their lipophilic nature allows them to cross the cell membrane; they are synthesized on demand

• bc the are lipophilic, they are hydrophobic, so they need to be bound to a protein to travel in the blood

albumins

A plasma protein that binds to the in the blood they are hydrophobic and carries them (steroid hormones )

Once a steroid hormone crosses the cell MB

It binds to either the cytoplasm or the nucleus, and then it binds to a hormone receptor complex

hormone receptor complex

When a hormone binds to a specific gene to be copied ( gene expression ), it acts like a switch to create new proteins. The new protein will give us the effect we want ( cause the cell to function differently)

zona glomerulosa

(aka the outermost zone of the adrenal cortex ) where aldosterone is secreted (mineralocorticoid)

aldosterone

important in regulating sodium and potassium & hydrogen ions when it happens in the kidneys

zona fasciculata

aka middle zone of the adrenal cortex, where cortisol is secreted ( glucocorticoid )

cortisol

imp for the way the body handles glucose, released during times of stress or chronic stress (stress hormone), affects the immune system

Zona reticulitis

The deepest zone of the adrenal cortex secretes androgens (and a little cortisol )

androgen

masculinizing hormone, DHEA also and androgene similar to testosterone but less effective

To control how much hormone is in the body the body must

break down and metabolize it, the kidneys and liver do a good job of this and release it in the urine

catecholamine and peptide hormones are hydrophilic, meaning they

dissolve in the blood, but they don’t last long and are broken down within minutes to hrs.

steroid & thyroid hormones are hydrophobic, meaning they must

bind to proteins, protecting them from quick degradation, which is why steroid hormones last for hours to days

thyroid hormones are an amine hormone but

They behave and act like a normal steroid hormone

water soluble hormones

like catecholamines and our peptide hormone find their receptors on the cell MB of their target cell

lipid soluble hormones find their receptors on the

nucleus of the target cell, where transcription of the gene takes place

upregulation

The response of a target cell to its hormones by increasing the number of receptors available on the target cell

• Usually activates after prolonged exposure to a small amount of the hormone

• will put more receptors to make sure every bit of the hormone binds to an receptor

premissivernes

The ability of one hormone to allow another hormone to exert its full effects, one hormone can affect the upregulation or deregulation of another hormone by changing their receptors, allowing the second hormone to have a weaker or stronger effect

explain this image

• The thyroid hormone is the permissive hormone that causes the upregulation of receptors for epinephrine ( more epi receptors)

• Estrogen is needed to progesterone to have the full effect of thickening the uterus lining

3 ways that endocrine cells are stimulated to release their hormones

• Change in plasma concentration of ions or nutrients

• Hormones can be changed through NT release in endocrine cells by neurons on endocrine cells

• Another hormone influences the secretion of another hormone

explain this picture

• When you eat, you break down glucose, making it abundant in your blood

• that stimulates the pancreas to release insulin, increasing insulin and releasing it into the blood

• signaling glucose target cells to put GLUT transporters on the cell membrane so they can take more glucose from the blood into the cell ( glucose uptake )

• decreasing the blood glucose levels

the adrenal medulla is a

modified sympathetic ganglion, when sympathetic neurons fire from the ganglion (adrenal medulla), epinephrine is released

hypothalamus is a

Another structure in the NS has control over; its neurons release their own hormones that affect the anterior pituitary secretions

• either release or inhibit the release of hormones

• The anterior pituitary is a tropic hormone structure, making the hormone it secretes a tropic hormone

• The hypothalamus also releases hormones into the posterior pituitary, but it just stores these hormones and releases them into the blood when needed

  • just stores, not produces

tropic hormone

A hormone that stimulates the secretion of another hormone

ex. Thyroid-stimulating hormone is released from the anterior pituitary, then travels to the blood to stimulate the thyroid gland to release thyroid hormones

• Overstimulation can lead to the enlargement of glands ( goiter)

The control of hormones is mostly done through

negative feedback loops

short negative feedback loop

The effect the anterior pituitary has on the hypothalamus’s secretion

• The hormone secreted by the anterior pituitary provides feedback to the hypothalamus

long negative feedback loop

looking at the influence that the third hormone in sequence will have on either the anterior pituitary secretion or the hypothalamus secretion

hyporesponsiveness

The target cell is no longer responding to the hormone

. ex., diabetes mellitus type 2: insulin is present in the body, but receptors don’t respond to it anymore (insulin resistance )

hyporesponsiveness is caused by

• receptor deficiency ( not enough receptors)

• signaling pathway problems ( the hormone binds to the receptors, but the signal doesn’t get picked up)

• lacking the enzyme to activate the hormone, being able to turn into the active form of the hormone ( eg., not being able to convert testosterone to DHEA )

hyperresponsiveness

A condition that causes the upregulation of receptors; the response to the hormone increases

ex. The thyroid hormone can act permissively, enhancing the effect of epinephrine and making a person more sensitive to epinephrine, increasing the HR

The hypothalamus has special neurons that release tropic hormones

• hormons os the hypothalmsu are either releasin or inhibiting hormones

• affecting the anterior pituitary to secrete its tropic hormones, which will have specific target sites of their own

hormones from the hypothalamus reach the pituitary through the

hypothalamo-hypophyseal portal vessels

hypothalamo-hypophyseal portal

• a portal system with two capillary beds connected by a vein

• the first capillary bed picks up trophic hormone, then enters the portal vein, then enters another capillary bed ( loc in anterior pituitary)

• quick route for hormones

other types of hormones in the hypothalamus

These hormones make ADH (antidiuretic hormone, aka vasopressin) & oxytocin ( peptide hormone), both of which are not tropic hormones

• These hormones are released directly into the posterior pituitary; they don’t have to be picked up in the portal system

Antidiuretic hormone ( ADH/vasopressin)

works in the kidneys, important in reabsorbing water, also increases BP by increasing blood volume

• Binds to smooth muscle over blood vessels, causing them to contract, increasing BP

oxytocin

Important in childbirth bc it helps with uterine contraction smooth muscle); also helps in milk ejection, aka milk letdown

• Released after childbirth bc its imp for mom and baby

hormones from the hypothalamus that control the secretion of the anterior pituitary ( explain pic )

either inhibiting or stimulating the hormone release by the anterior pituitary

• increase adrenocorticotropic hormone

• increase thyroid hormone

• increase growth hormone

• increase follicle-stimulating hormone & luteinizing hormone

• increase dopamine and decrease prolactin

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are

are gonadotropins, affect the gonads and impact the production of sex hormones and cells

growth hormone ( GH)

Affects many parts of the body; important for growth, protein synthesis, carbohydrate and lipid metabolism, bones, muscle, and skin

• Also stimulates the liver to produce something similar to GH, like insulin ( IGF, insulin-like growth factor ), which kind of acts like insulin

thyroid gland`

• loc inferior to the thyroid cartilage has two different types of cells

  • follicular cells

  • parafollicular cells

follicular cells

Surround the sphere-shaped structure called a follicle. Within the follicle, there is a thick protein called colloid

thyroglobulin

made by follicular cells and is the main component of the colloid and also makes the main scaffolding of thyroid hormones

thyroxine (T4)

A hormone made by follicular cells has 4iodines; makes more of this 80% but is in active form

• Converted to T3 at the target site; target cells contain an enzyme called deiodinase, and deiodinase T4 into T3

triiodothyronine ( T3)

3 iodines; the active form is the ( 20%)

thyronine ( T4) and triiodothyronine ( T3) both are made of

tyrosine, amine hormones, but also needs iodine

thyroid hormone

Will have receptors on most of the cells bc its important for metabolic activities

• Absorption of carbohydrates in the small intestine

• Release of fatty acids from adipocytes

• stimulation Na/k pump

all the things listed also help in normal growth and brain development

metabolism

how our cells utilize the breakdown of glucose

permissive action of the thyroid hormone

Upregulating epinephrine also raises body temp

T3 is important for the development of the

NS and producing GH

cretinism

due to a lack of iodine in the mother’s body

hypothyroidism

Decreased levels of T3 and T4, due to damage or destruction of the thyroid gland or deficiency of iodine in the diet

• The low level of thyroid hormone will negatively feedback to the hypothalamus and the anterior pituitary, causing an increase in the thyroid-releasing hormone from the hypothalamus, increasing thyroid-stimulating hormone from the anterior pituitary

Hashimoto’s disease

Common in areas that have a deficiency in iodine, hypothyroidism, cold sensitivity, weight gain, fatigue, and autoimmune disease, where the immune system attacks the thyroid gland

hyperthyroidism

Increased level of T3&4, due to a tumor or Graves disease ( an autoimmune disorder, where the immune system creates antibodies that bind to receptors on the thyroid gland, mimicking TSH, causing overstimulation of the thyroid gland

• Weight loss, increased metabolic activity, more sensitive to heat, increased heart rate, tremors, exophthalmos ( fluid behind the eye increases)

primary hypersecretion /hyposecretion

The endocrine gland itself is producing too much or too little of a hormone

secondary hypersecretion/hyposecretion

due to an increase or decrease of a tropic hormone ( in the anterior pituitary specifically) caused by problems in either the anterior pituitary or the thyroid gland

cortisol

known as the stress hormone, released during times of stress, can include extreme temps, infection, starvation, excessive exercise, and emotional stress

explain this photo

• Neural input from a stressor enters the hypothalamus, causing the hypothalamus to release CRH (corticotropin-releasing hormone)

• travels in the blood through the portal system to enter the anterior pituitary

• causing the anterior pituitary to increase the production of ACTH

• ACTH is dumped into the blood and is recorded as elevated by the adrenal cortex when it arrives, stimulating the adrenal cortex to release more cortisol

• causing blood cortisol level to increase, cortisol affects all parts of the body and is released continuously throughout the day ( not just during times of stress), but is released in smaller amounts and is important for other functions like homeostasis, permissive action on epi and norepinephrine (upregulates the receptors of both on the smooth muscles of blood vessels) to maintain normal BP

Cortisol helps maintain blood glucose by

working in the liver it help make glucose between meals (using glycogenolysis)

cortisol also has an effect on the immune system,

weakens the immune sus it has anti-inflammatory properties, and is why a synthetic form of cortisol called cortisone is used for inflammatory conditions like arthritis

High cortisol levels for a long time can also cause

• Fertility issues and delayed growth in adolescence

• can also cause cancer & activate autoimmune disorders

cortisol is also very important during development in the

womb and life after birth ( neonatal life ) helps produce surfactant, which helps prevent the collapse of small air sacs in the long, helping inhale & exhale air

adrenal insufficiency

meaning critically low levels of cortisol, which causes profound effects on the body, including low blood glucose, weight loss (not healthy), weakness, and increased susceptibility to ilness bc of the way it affects the immune system/ ( Addison disease)

causes include

• primary adrenal insufficiency

• secondary adrenal insufficiency

primary adrenal insufficiency

An issue within the adrenal cortex, the adrenal cortex is attacked by the immune system, destroying the cells within the cortex, leading to a decrease in cortisol and aldosterone (Addison’s disease)

secondary adrenal insufficiency

problem with the anterior pituitary, where it underproduces ACTH, causes a decrease in cortisol

Cushing syndrome

The opposite of Addison’s disease: excess secretion of cortisol caused by a tumor in the anterior pituitary causing an excess of ACTH secretion, or a tumor within the adrenal gland itself

Symptoms - moon face ( excess fat in the cheeks ) redistribution of more fat around the belly and near the nape of the neck and upper back, giving a buffalo hump, causing striae (stretch marks), muscle wasting, not treated, developed diabetes, high blood pressure, osteoporosis ( brittle bones disease)

dont want insuline in the blood during times of stress because

We want to keep glucose levels elevated and insulin decreases them

beta endorphins

has pain-killing effects, helps the body deal with pain during times of stress

Hormone influence of growth (explain this pic)

What other hormones must be present for proper growth

• Insulin-like growth factor (released from the liver and influenced by GH

• T3 (thyroid hormones)

• sex hormone (testosterone and estrogen)

GH is released by the ___ and controlled by the release of GHRH release by the ___

anterior pituitary, hypothalamus

somatostatin

Growth hormone-inhibiting hormone inhibits growth hormone; when IGF-1 increases, it creates a positive feedback loop to the SST, slowing down the release of SST

triiodothyronine ( T3)

Important for GH synthesis: direct influence of chondrocyte differentiation & blood vessel formation on chondrocytes

• Influencing and supporting chondrocytes for growth to occur

insulin

Has an anabolic effect, stimulates fat storage & inhibits the breakdown of protein; if you have too much insulin, you are going to have more fat storage

• If you are consuming a lot of fatty food and a lot of sugar, you’re going to have higher insulin levels, meaning more fat storage

sex hormone

Stimulates both GH & IGF -1

which :

• increase muscle mass ( based on gender)

• stop growth at the epiphyseal growth plates ( so we’re not growing all our life ); close the growth plates

cortisol

decrease growth ( only hormone that does that ), can do this be its catabolic stress effects on proteins and also inhibits DNA synthesis within cells

pituitary adenomas

tumor in the pituitary gland (specifically anterior pituitary)

gigantisms

an overstimulation of the cells that secrete growth hormones, in children causing excessive bone growth

acromegaly

If it occurs in adults after they are already grown, it causes enlarged hands and feet, and facial bones

Osteoblasts

lay down a substance called osteoid; osteoid has to be mineralized to become the matrix of bone ( solid bone )

Osteoclasts

are larger cells in the bone responsible for breaking down the matrix of the bone so that they can release calcium into the blood

kidneys ( Ca)

• filtering & reabsorbing most of our calcium

• control how much calcium is reabsorbed back into the blood

GI tract ( Ca)

regulate how much calcium we absorb from the gut (from food)

parathyroid gland

• loc on the posterior surface of the thyroid gland

• Important for calcium regulation; regulates it by pumping it in and out

has several effects

• increases bone resorption, increasing osteoclast activity, breaking down more bone and releasing Ca and phosphate into the blood

• also stimulates the kidney to release an active form of vitamin D (1,25-dihydroxy vitamin D) to help reabsorb Ca. Necessary for pumping absorption from the lumen of your small intestine across the wall into the blood

• Reabsorbing into kidney tubules and peeing out the phosphate

Low calcium levels are the stimulus for

the release of parathyroid hormone

calcitonin

Released by the thyroid gland, but not by follicular cells; released by parafollicular cells in the gland

• Stimulation is an elevated blood calcium level

• Decreases calcium level by decreasing osteoclast activity