THE ENDOCRINE SYSTEM

The Nervous System’s Cousin

OBJECTIVES Differentiate between endocrine and

exocrine Describe the structure and function of

various endocrine glands and their corresponding hormones

Determine how hormones are recognized by receptors and can alter cellular function

Differentiate between steroid and peptide hormones

Explain what negative feedback means within the endocrine system

WHAT IS IT? 2nd greatest controlling

system of the body

Works closely with what other system?

Works slowly by secreting chemical messengers called hormones throughout the circulatory system that tell the body what to do

ENDOCRINE VS. EXOCRINE Endocrine glands- ductless glands that

produce hormones that release into blood or lymph circulationPituitary, hypothalamus, thyroid,

parathyroid, adrenal, pineal, thymus, gonads, and pancreas

Exocrine glands- release their products at the body’s surface or into body cavities through ductsSweat and oil glands; pancreas; liver

HORMONES Chemical messengers secreted by

endocrine glands that diffuse into the bloodstream and act on target cells some distance away

“Local hormones” that function similarly to hormones but are not technically hormones:Paracrine – only affect neighboring cellsAutocrine – affect only the secreting cell

(itself)

WHAT DOES THE E.S. DO? Many hormones, many functions

ReproductionGrowth and developmentMetabolismNutrient, water, and ion balance

Ongoing processes Equilibrium Feedback loops

EQUILIBRIUM What does it mean to have a “hypo”

condition?

What does it mean to have a “hyper” condition?

Your body wants to be in equilibrium to function properly; when there are hypo/hyper conditions, hormones are released to bring the body back to normal!

WHAT HAPPENS WHEN EQUILIBRIUM CAN’T BE ACHIEVED? Disease/disordered state

http://www.pbs.org/wgbh/nova/body/obesity.html

What can cause this to happen?Problems with synthesis or secretion of the

hormoneProblems with the hormone’s receptor

protein

FEEDBACK LOOPS How blood levels of hormones are regulated

by maintaining homeostatic function

Negative feedback mechanism If you have high levels of leptin in your body,

what happens?

High levels of hormone in the blood stream will “feedback” to the source and tell the gland to stop producing the hormone

Turns itself off

LEPTIN NEGATIVE FEEDBACK

POSITIVE FEEDBACK IS RARE If negative feedback shuts down hormone

production after a large amount is detected in the blood stream… what does positive feedback do?Process of amplification where an increase in

hormones causes an increase in the response The body goes further away from equilibrium

Hormone known to exhibit positive feedback:Oxytocin stimulates uterine contraction in

childbirthOxytocin promotes milk letdown in nursing

mammals

TYPES OF HORMONES Steroid

Hormones: Made from

cholesterol Includes hormones

made in the adrenal cortex (cortisol & aldosterone)

Includes hormones made in gonads (testosterone & estrodial/estrogen)

TYPES OF HORMONES Peptide Hormones

Consist of amines, peptides, proteins

Made from amino acids

What differences do you notice between peptide and steroid hormone structure?

COMPARE & CONTRAST

Steroid Hormones Peptide Hormones

MAKE A CHART TO USE AS A TOOL TO REMEMBER (PG. 301)Steroid vs. Peptide Hormones

Water soluble? Lipid soluble? Ability to pass through cell

membrane? Site of formation of hormone-

receptor complex? (where do they bind?)

How does it work? Half-life?

HORMONE TYPE COMPARISON CHART

Steroid Hormones Peptide Hormones

Insoluble in water (doesn’t dissolve)

Soluble in lipids (does dissolve)

Can pass through the phospholipid cell membrane but cannot travel in the aqueous bloodstream without a protein carrier

Soluble in water Insoluble in lipids Cannot pass

through the phospholipid cell membrane on its own but can travel in the aqueous bloodstream alone

CONTINUED

Steroid Hormones Peptide Hormones

Hormone-receptor complex binds in the nucleus

This causes specific genes to be activated to make specific proteins coded for by the genes

Long half-life

Hormone-receptor complex binds on the cell membrane (cannot pass through)

This causes a cascade of events triggering a 1st messenger protein, which triggers a 2nd messenger, eventually activating proteins to alter cell activity

Very short half-life

THE PITUITARY GLAND

Broken down into 3 parts

OBJECTIVES Describe the structure of the pituitary

and label which hormones are released in each section

Describe the function of the pituitary hormones

Recognize various pathologies related to pituitary hormone imbalances

PITUITARY GLAND LOCATION Located at the base of the brain where

the pituitary stalk attaches to the hypothalamus

1 cm in diameter

PITUITARY GLAND Anterior Pituitary Intermediate Pituitary

Not as functional in humans Posterior Pituitary

INTERMEDIATE PITUITARY Produces melanin stimulating hormone

(MSH) Stimulates melanocyte cells to produce

melanin What does melanin do?

Pigment in the skin and in portions of the eye and brain

MSH is increased in exposure to UV light

Disappears during fetal development, but its cells become parts of the two remaining lobes

POSTERIOR PITUITARY Neuronal

Neural-endocrine hormones are produced in hypothalamus and stored in posterior pituitary

Post. Pit. hormones are released upon stimulation by hypothalamic neurons Supraoptic nucleus (SON) Paraventricular nucleus (PVN)

Even though they are made in the hypothalamus, the post. pit. hormones are named so because that is where they enter the bloodstream

POSTERIOR PITUITARY HORMONES Antidiuretic hormone (ADH)

Sometimes called Vasopressin Oxytocin (OT)

ANTIDIURETIC HORMONE (ADH) Background info:

Diuretic- chemical that increases urine production Antidiuretic- chemical that decreases urine formation

Peptide hormone

Released by the Post. Pituitary when SON is activated

How can ADH prevent urine production? What organ may ADH target? ADH produces an antidiuretic effect by reducing the

volume of water the kidneys excrete Overall, regulates the water concentration of body

fluids

ADH FUNCTION Osmoreceptors in the brain sense changes

in the osmotic pressure of body fluids

ADH FUNCTION When dehydrated, concentration of

blood solutes (ions, salt, sugar) increases, which increases osmotic pressureTargets kidneys to reabsorb more water into

the bloodstreamConcentrates urine (low volume of urine,

higher blood volume) Increases blood pressure by constricting

arterioles in kidneys to allow for more water to be absorbed

Drinking too much water dilutes body fluids, inhibiting ADH

ADH PATHWAY

ADH DISRUPTORS Diuretics cause water to be flushed out

of the body through urine Can you think of any diuretics?

Antagonists of ADH

Thinking question: College students typically drink excessive amounts of alcohol and walk from bars back to their apartments. Why is this dangerous in the winter? Think about ADH!

HYPO-ADH If the SON is damaged lowering the

secretion of ADH…What will happen?

Pathology called Diabetes InsipidusFrequent urination; kidneys don’t reabsorb

waterExcessive, continual drinkingContinual thirstNot necessarily life threatening unless don’t

drink enough water

OXYTOCIN HORMONE Peptide hormone Synthesized in the hypothalamus,

released by the Post. Pituitary when stimulated by the paraventricular nucleus (PVN)

Hormone involved in + feedback Made in significant amounts in childbirth

and nursing women

OXYTOCIN FUNCTION Stimulates uterine contractions in

childbirth & “milk letdown reflex” in nursing mothers

Nursing mothers often get cramps while nursing after childbirth due to high levels of oxytocin released

Synthetic oxytocin drugs are used to induce labor by mimicing oxytocin (Pitocin)

“Mother/Father Love hormone” or “Bonding hormone”

OXYTOCIN TREATMENTS… For relationships?

Boyfriend blues?... Oxytocin is not the cure Women with less oxytocin receptors in their

brain show not as many affectionate behaviors toward significant other

For anorexia Anti-anxiety drug possibility; help fight food

fixations For autism

Helpful in boosting emotional recognition Still in the research phase http://www.scientificamerican.com/article/be-m

ine-forever-oxytocin/

OXYTOCIN PATHWAY

ANTERIOR PITUITARY Glandular tissue, purely endocrine

function

Makes many peptide hormones:

Growth Hormone (GH) Prolactin (PRL) Follicle Stimulating Hormone (FSH) Luteinizing Hormone (LH) Adrenocorticotropic Hormone (ACTH) Thyroid Stimulating Hormone (TSH)

LH & FSH Function in reproductive endocrinology

FSH (follicle stimulating hormone)- stimulates follicle development in female ovaries & stimulates sperm production in males

LH (luteinizing hormone)- triggers ovulation in female ovary monthly & stimulates testosterone production in males

LH & FSH- COMPLICATED PATHWAY

HYPOSECRETION OF FSH/LH Infertility of males and females Some fertility treatments increase levels

of FSH or LH Multiple births due to increase in these

gonadotropic hormones causing multiple ovulations a month

GROWTH HORMONE (GH) Hormone that controls metabolism,

building up muscles and uses glycogen & fats for energy

Anabolic function Plays role in bone and skeletal muscle

formation

PATHOLOGIES Hypo-GH

What does this mean?Pituitary Dwarfism is hypo-GH in childhood

4 feet tall, proportional body

Hyper-GHWhat does this mean?Gigantism is hyper-GH in childhood

8-9 feet tall, proportional body Acromegaly is hyper-GH after long bone

growth has ended in adulthood; facial bones continue to grow; non-proportional growth

GH PATHOLOGIES Gigantism Acromegaly Dwarfism

PROLACTIN (PRL) Stimulates and maintains milk

production in mother’s breasts after childbirth

Inhibited by dopamine (high levels of dopamine = no milk production)

Prolactinomas- increase milk production; can occur in males too

THYROID STIMULATING HORMONE (TSH) Influences the activity of the thyroid

gland by stimulating the release of T3/T4 (thyroid hormones)

ADRENOCORTICOTROPIC HORMONE (ACTH) Regulates the endocrine activity of the

adrenal cortex

THE THYROID GLAND

And the Parathyroid Glands

OBJECTIVES Describe the structure and function of

the thyroid gland Describe the function of the T3/T4

thyroid hormones Describe the function of the C cell’s

Calcitonin hormone Explain the function of the parathyroid

gland and secreted parathyroid hormone

Recognize thyroid and parathyroid hormone pathologies

THYROID GLAND Located at the base of the throat below

the Adam’s apple around the esophagus Sticky colloid-filled follicles where

thyroid hormone is made C (parafollicular) cells is where

calcitonin is made

THYROID HORMONES T4

Thyroxine has 4 Iodines (the major form) T3

Triiodothryonine has 3 Iodines Both T3 and T4 have similar functions T3 is five times stronger than T4

Thyroid collects iodine in order to make T3/T4 hormonesWhere do you get iodine?

THYROID HORMONES (T3/T4) Function in cellular metabolism

Controls the rate at which glucose is used for body heat and chemical energy

If a lot of thyroid hormones are made, metabolism will increase

Basal metabolic rate (BMR)Determines how many calories the body

must consume at rest in order to maintain life

Every cell in the body is a target for T3/T4 (the thyroid hormones)

THYROID HORMONE PATHWAY Draw it out

Anterior pituitary releases TSHTSH goes to ThyroidThyroid releases T3/T4

How do they feedback?

HYPERTHYROIDISM Hyperthyroid:

Goiter forms due to overactive thyroid

Swelling of eye socket tissue bulging eyes

Irritable, hyperactive, insomnia, high body temp., ravenous

Grave’s Disease (autoimmune disorder) can be a cause of hyperthyroid

HYPOTHYROIDISM Too little T3/T4:

Possible cause is Iodine deficiencyCommon before “iodized” salt Goiter due to constant TSH in thyroidWeight gain, lowered body temp., lethargy,

slower pulse

CALCITONIN (CT) Protein hormone Made in the C cells in the connective

tissue between the thyroid follicles

Decreases blood calcium levels by putting calcium deposits in bones

If blood calcium levels increase, CT is released to lower them again

PARATHYROID GLANDS & PTH 4 tiny yellow glandular tissue masses on

outside of the thyroid gland Secretes parathyroid hormone (PTH), a

protein hormone, which is another regulator of blood calcium levels

PTH PTH works antagonistically with CT…

what does this mean? Functions in raising calcium levels in the

blood if they drop below a certain level by causing osteoclasts in bone to break down bone matrix to release calcium

PTH also stimulates kidneys and intestines to absorb more calcium from food

CT AND PTH PATHWAY

PTH AND CT PATHOLOGIES Severe hyperparathyroidism- breakdown of

bone matrix, increased osteoporosis, and broken brittle bones

Severe hypothyroidism results in death due to low Ca2+ levels Nervous system failure; uncontrollable spasms

(tetany) Can actually remove parts of PTH tumors and

place remaining healthy parathyroid gland on the skin and it will function normally!

Low CT in elderly adults (possible link to osteoporosis) Take salmon calcitonin supplements

THE ADRENAL GLANDS

Consisting of the Adrenal Cortex and Adrenal Medulla

ADRENAL GLANDS Located on top of the

kidneys Adrenal cortex- outer

portion of adrenals that is purely glandularMakes steroid endocrine

hormones Adrenal medulla- inner

region consisting of neuroendocrine tissueMakes neurotransmitters

epinephrine and norepinephrine

ADRENAL CORTEX Makes 3 main groups of steroid

hormones called corticosteroidsMineralocorticoidsGlucocorticoidsSex steroids

Cannot survive without adrenal cortex

MINERALOCORTICOIDS ALDOSTERONE Functions in regulating salt concentration

in the blood (Na+ and K+) Higher aldosterone leads to increased

absorption of Na+ into blood and release of K+ into urine

What organ do you think this hormone targets? Kidneys- selectively absorb ions or allow

them to be flushed out in urine Help regulate water and electrolyte

balance in blood

HYPERALDOSTERONE Hyperaldosterone- water & Na+

retentionAbnormally high amount of water and

sodium in blood leads to HIGH blood volume and HIGH blood pressure

Heart has to work harder!Usually due to a tumor; must be removed

HYPOALDOSTERONE Addison’s Disease-

hypoaldosterone Sodium and water are lost,

electrolyte imbalance, weakened muscles, tiredness, bronze skin

Low blood glucose, dehydration, low blood pressure

Can lead to deficiency in glucocorticoids (cortisol)

Lethal within days without treatment of adolsterone and cortisol hormone replacement shots

Excess unused ACTH leads to

buildup of melanin

GLUCOCORTICOIDS CORTISOL, sometimes called the stress

hormone

Produced in the middle adrenal cortex Without cortisol, a person will not survive

Raises blood glucose levelsLiver breaks down excess amino acids to

glucosePromotes fatty acid breakdown (rather than

glucose break down) for metabolism

CORTISOL Suppresses immune system by

counteracting inflammatory responseHydrocortisone Cream- reduce swelling &

itchingSteroid injections for extreme cases of

swelling/immune responses Poison ivy, eczema, swollen/bulged disks in

back, etc.

Organ transplant patients receive high doses of cortisol-like steroids (dexamethasone) to prevent immune response against foreign organ

HYPERCORTISOL Cushing’s Disease- HYPERcortisol

disorderMore likely to develop Diabetes due to high

blood glucoseHigh blood pressure (due to high blood

glucose)Fat deposits at waist, buffalo hump, moon

faceHigher susceptibility to infectionNormally accompanied by an excess in

adolsterone as well Swelling

HYPOCORTISOL Extreme Addison’s disease is also linked

to low cortisolUsually when low in adolesterone, low in

cortisol too Hypoglycemia (low blood glucose levels) Inability to deal with stress

SEX HORMONES Both male and female sex hormones

produced by innermost adrenal cortex Sometimes called sex steroids Androgens- male sex hormones are

produced in both males and females but at a higher level in males

Estrogens- female sex hormones produced in both sexes but higher quantity in females

ADRENAL MEDULLA Secretes epinephrine and

norepinephrineWork together to do the same job

Increase heart rate, breathing rate, blood glucose level, elevate blood pressure, and decrease digestion

Sympathetic nervous system stimulates adrenal medulla

Fight or flight

OVARIES AND TESTES

The Sex Hormones

SEX HORMONES Most of the androgens, like

testosterone, is produced by the testes in males

Most of the estrogen and progesterone is produced by the ovaries in females

TESTOSTERONE Made in the testes

Increase primary and secondary sex characteristics

Testosterone plays role in building muscleAnabolic steroids

If females overproduce androgens in adrenals or can’t convert testosterone to estrogen, can show characteristics of malenessMasculinization regardless of the sex

ESTROGENS & PROGESTONE Made in the ovaries 3 types

Normal estrogen, 1 in pregnancy, 1 in menopause

Primary and secondary sex characteristics in females

Necessary for egg development

Progesterone is necessary for ovulation

PROGESTERONE Synthetic progesterone called progestin

in birth control pills Taken daily with makes the body think

that it is pregnant thus ovulation ceasesNear the end of monthly cycle, if egg is not

fertilized and implanted in uterus, progesterone levels lower and the cycle starts again

If levels do not decrease, the cycle will not start again

MALE CONTRACEPTIVE? Male birth control by regulating

hormonesBlock FSH receptors?Block FSH secretion?

Possibly interfere with inhibin Another male hormone involved in sperm

development

PANCREASA review from semester 1

PANCREAS Exocrine- releases

digestive enzymes Endocrine- releases

hormones

Posterior to stomach and attached to first section of small intestine (duodenum)

PANCREAS Pancreatic islets- (Islets of Langerhans)

endocrine portion of the pancreas that consists of two types of cells closely associated with blood vesselsAlpha cells

Secrete glucagonBeta cells

Secrete insulin

GLUCAGON Stimulates liver to break down glycogen

into glucose to raise blood sugarEpinephrine can also do this (not as

efficiently) Low blood glucose triggers the release

of glucagon

Glucagon prevents hypoglycemia between meals and during exercise

INSULIN Stimulates the liver to MAKE glycogen

from glucose and to uptake glucose from the blood stream into cells

Lowers blood glucose levels Prevents hyperglycemia High blood glucose levels trigger the

release of insulin

Glucagon antagonist

DIABETES MELLITUS Lack of insulin or the inability of cells to

recognize it Insulin deficiency disrupts carbohydrate,

protein, and fat metabolism Symptoms- hyperglycemia leading to

kidneys excreting sugar in the urine; sweet breath; polydipsia (extreme thirst); weight loss; hunger increase; ketoacidosis (low blood pH)

TYPE 1 DIABETES MELLITUS Usually before the age of 20 and is

autoimmune where the immune system attacks the beta cells of pancreas (so they cannot make insulin)

Insulin dependent- shots/pumps are required

Islet replacements can be placed in liverProcedure is risky and rarely successful;

thus hormone replacement is the best choice for treatment

TYPE 2 DIABETES MELLITUS Beta cells produce insulin but the body

cells lose the ability to recognize it 85-90% of people with diabetes have

Type 2 Usually correlated with overweight

people over the age of 40 Treatment: diet, exercise, oral drugs to

control glucose levels, possible insulin shots