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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