Endocrine SystemIman AwanMeighan TutenMackenzie Weeks

Endocrine System• Includes hormones, hormone secreting glands, and the target

cells molecular receptors.• Responds to change with chemical signals in order to maintain

homeostasis, like the nervous system.• Largely composed of glands.• These glands secrete hormones which are carried through the

bloodstream.• The endocrine system is a slow, but prolonged response

Endocrine Glandsvs. Exocrine Glands• Endocrine Glands: Secrete products into the bloodstream to

deliver them throughout the body.• Exocrine Glands: Have ducts which they secrete their products

into. These ducts then take the products to the lumens of the other organs or outside the body.

Hormones• A means of communication between cells, body parts, and

individuals.• Affect the metabolism of cells with receptors to receive them.• Most hormones act at a distance between body parts and

travel in the bloodstream, for example, testosterone.

Action of Hormones• Effects of Horomones:-Can induce a target cell to increase its uptake of a particular

molecule like glucose, ions, or calcium.-Can bring alteration to the target cell’s structure. -Can influence cell metabolism

Action of Peptide Hormones

• In muscle cells, the reception of epinephrine leads to the breakdown of glycogen into glucose. This provides energy for ATP production.• Epinephrine never actually enters the cell, so is called the

first messenger.• Cyclic adenosine monophosphate (cAMP): The

immediate result of binding and contains one phosphate group attached to adenosine at two locations.• cAMP sets the metabolic machinery in motion, so it is

called the second messenger.• http://www.youtube.com/watch?v=-gUC7ZQTp34

Protein Hormones• More commonly known as Peptide Hormones• Made up of amino acids • Water soluble• Tend to be Globular (Ball like shape)• Can’t pass through membranes• Bind to receptors on the outside of cells, which trigger a

response on the inside

Examples• Antidiuretic Hormone(ADH)- “tells” the kidney to reabsorb

more water. ADH is made by the hypothalamus.• Angiotensin- makes the kidney reabsorb more NaCL and

water. Lowers blood pressure.• Aldosterone- absorbs Na+ and water. Produced by the Adrenal

gland, it increases blood pressure. • Glucagon- increases glucose levels in the blood, by hydrolyzing

in the liver. Is produced by the pancreas.

Examples Cont.• Insulin- decreases glucose levels in the blood, by storing

glucose and glycogen in the liver. Is also produced by the Pancreas.

• Calcitonin- produced by the thyroid, it decreases Ca+ levels in the blood by storing Ca+ in bone and allowing the kidney to urinate more Ca+ out.

• Adrenaline- produced by the adrenal glands. Acts as the fight or flight hormone.

Examples Cont. • PTH- parathyroid hormone, produced by the parathyroid. This

increases blood Ca+ levels by accessing stored Ca+ in bone and telling the kidney to reabsorb more Ca+ ions.

• Oxytocin-produced by the hypothalamus, released by the posterior pituitary. It causes uterine contractions during labor.

Steroid Hormones• Type of hormone that has the same complex of four carbon

rings, but each one has different side chains.• Produced by the cortex, the ovaries, and the testes.• Because they are lipids, they can enter the cell.• Once inside the cell, they can bind to a receptor, usually in the

nucleus.

Examples• Gonadotropin-releasing hormone(GnRH)- produced by the

hypothalamus. “Tells” the pituitary to make FSH & LH.• FSH- follicle stimulation hormone; aids in egg and sperm

development. Made by the pituitary and under control of GnRH levels.

• LH- luteinizing hormone. Tells the gonads to either release estrogen or testosterone.

Examples Cont.• Progesterone- is secreted by the corpus luteum and by the

placenta and is responsible for preparing the body for pregnancy and, if pregnancy occurs, maintaining it until birth by thickening the uterine lining.

• Estrogen-secreted by ovaries, develops eggs and is responsible for the secondary sexual characteristics in females.

• Testosterone-helps sperm develop; responsible for the secondary sexual characteristics in males.

http://www.youtube.com/watch?v=AhVRNbcaTIA

Cell Communication

• Cells communicate with each other through direct contact or chemical signaling.• Endocrine signals release hormones which travel

through the bloodstream towards receptors located in different parts of the body.• Thyroid hormones (from thyroid to the brain)• Insulin (from pancreas, bind to cells)• Testosterone• Estrogen• Human growth hormone

Signal Transduction Pathways

• Transduction- the act of transferring genetic material from one cell to another

Changes in Signal Transduction Pathways & Their Effects

• Faulty signal transduction pathways can lead to a number of diseases.• Cancer- altered signal transduction pathway which

works with a protein regulating cell growth• Diabetes- altered/ blocked transduction pathway

working with insulin producing cells and receptors• Heart disease- if signals initiating processes are not

received or not punctual, muscular rhythm may be affected• Autoimmune disease- signals are not communicated

or precise enough and the immune system overreacts to substances normally present in the body

The Biological Clock

• Organisms respond to their external environments. Timing and coordination of these physiological events are regulated.• The cycle of circadian rhythms, or the 24 hour

physiologic cycle, is present in all eukaryotes and takes place even without external cues• Circadian rhythms affect our entire bodies, but

disruptions can lead to hormone imbalance and reversed day/night cycles. Ex: night workers have higher levels of melatonin, “hormone of darkness”• Nocturnal/Diurnal- pineal gland releases melatonin, a

hormone that regulates sleep and wake cycles

Homeostasis & the Endocrine System

• Homeostasis involves maintaining the internal environment between limits- deficiencies and overproduction

• Maintaining blood pH, body temperature and water balance, concentration of carbon dioxide, concentration of blood glucose by use of negative feedback mechanisms

Homeostasis & the Endocrine System

• Organisms use negative feedback mechanisms to maintain their internal environments (blood & tissue fluid) and respond to the external environmental • Negative feedback mechanisms: glands within the

endocrine system that stimulate the release of a hormone from another gland are eventually shut off to prevent hormone imabalance and hormone excess. Ex: A triggers B, B triggers C, C triggers A to shut off• Graves disease- a disease in which there is an

overproduction of thyroid hormones• Diabetes Mellitus- decreased insulin

Body Temperature• The hypothalamus responds to signals from temperature

receptors and releases temperature-decreasing or temperature-increasing procedures until body temperature is controlled.

• Vasodilation- small blood vessels, or arterioles, in the skin open to allow blood to flow freely near the surface of the skin. This allows some of the heat in the blood to be transferred to the external environment as long as the external temperature is lower than that of the blood (98.6° F) ; pink coloration.

• The primary form of cooling in humans is the use of sweat glands. Eccrine sweat glands are small, tubular structures of the skin that secrete sweat; apocrine sweat glands are simply much larger and located in the armpits.

• Shivering- muscle groups around vital organs begin to shake in order to create warmth by expending energy. Primary motor center (hypothalamus) is activated by cold signals from the nervous system and responds.

Blood Glucose Concentration• The concentration of sugar in the blood- either extreme can

be harmful.• After eating, carbohydrates and other sugars are broken down

into glucose- the simple sugar that provides the body with energy.

• Insulin proteins (secreted by islet cells in the pancreas) bind to cells which then activate receptors. These receptors absorb glucose from the blood stream into the cell for energy.

• Glucagon proteins stimulate the breakdown of glycogen in the liver into glucose; when blood sugars begin to fall, glucagon is released to counter the effects.

• Alpha and Beta cells are located in the islets of Langerhans in the pancreas.

• Alpha cells produce glucagon; about 15-20% of cells.

• Beta cells make and release insulin; about 65-80% of cells.

http://www.google.com/url?sa=i&rct=j&q=pancreas+and+insulin&source=images&cd=&cad=rja&docid=lSUogTiySmLOdM&tbnid=uWVIILoXVawf_M:&ved=0CAUQjRw&url=http://www.gopetsamerica.com/anatomy/pancreas.aspx&ei=FENbUb7RD8Ge2AXFu4DYAg&bvm=bv.44697112,d.aWc&psig=AFQjCNGp2dTAp1EQgjNIDYM3ohUJ8MYIZg&ust=1365021227333241

Diabetes• More than 18.2 million people in the world have diabetes;

that’s 6.3% of the population.• A chronic condition that can be fatal if not properly attended

to.• What is diabetes?• Diabetes is a disease in which the pancreas does not produce

insulin or the body does not use insulin properly.• Insulin is needed to convert sugars and starches into energy that

the body can use.• Symptoms include: excessive thirst/urination, lethargy, sudden

weight loss, fruity-sweet breath, sugar in urine• 3 types: Gestational diabetes (insulin resistance during

pregnancy, caused by excessive hormone production or inability to produce additional insulin ), Type 1 (T1D), and Type 2 (T2D

Type 1 Type 2• Adolescent onset• Pancreas stops making

insulin • Insulin dependent• Generally genetic/

environmental triggers• Treated by monitoring

blood glucose (concentration of sugar in blood) and insulin injections (pen or vial)

• Adult onset (45+)• Body can’t use insulin

effectively • Non insulin dependent• Generally a result of eating

habits (cells don’t absorb sugar properly)

• Treated by exercise, diet changes, and/or insulin injections

• Increasing in today’s population- could be a result of individuals consuming a very different diet to that of their ancestors

Effects of Diabetes• Long term side effects of excess sugars in the blood for long

periods of time can eventually damage the eyes, heart, blood vessels, kidneys, and nerves.

• FDA approved a new drug that costs about $8.77 per tablet; this releases blood sugars through excretion of urine

• Costs- one short-term insulin pen costs around $70 (2-3 weeks)one long-term insulin pen costs around $161(2 weeks) blood glucose testing strips cost about $1 a piece ( min 5-6 test strips/day)in addition, doctors visits are required once every 3 months

Genetics & The Endocrine System

• The inheritance pattern of some traits cannot be explained by Mendelian genetics.• Traits are sex-limited, and expression depends on the

individual• Milk production in female mammals• Pattern baldness in males

• Sex-limited traits can be associated with gender-specific hormones- these limit secretions, scents, growth, etc.• Increased testosterone in males• Increased estrogen in females

Hypothalamus• Hypothalamus: regulates he internal environment through the

autonomic nervous system.• Helps regulate heartbeat, body temperature, water balance• Controls sections of pituitary gland which is a small 1 cm

gland that is connected to hypothalamus by stalklike structure

Pituitary Gland• Posterior Pituitary

• neurons in the hypothalamus produce hormones called antidiuretic hormones, along with oxytocin

• these hormones pass through axons in posterior pituitary gland then being stored in axon endings

• Neurons in hypothalamus are sensitive to water salt balance in blood and when it is too high, ADH is released from posterior pituitary gland. When it reaches the kidneys ADH makes water become absorbed and as the blood is diluted, ADH is no longer released as it is no longer needed. This is called negative feedback where effect of hormone acts to shut down the release of another, helping to maintain homeostasis

• Not producing ADH leads to diabetes insipidus where a lot of urine is produced with loss of ions from blood. ADH being released is inhibited by consumption of alcohol explaining why people urinate a lot when they drink alcohol.

• Oxytocin is the hormone that causes uterine contractions during childbirth and milk letdown when a baby is nursing. The more the uterus contracts, more nerve impulses reach the hypothalamus and cause oxytocin to be released. • the release of oxytocin is controlled by positive feedback where the stimulus keeps making an effect occur

that increases intensity. • Can also play a role in propulsion of semen through reproductive tract in males which can affect emotions

and sexual satisfaction

Pituitary Gland

• Anterior Pituitary• Considered a portal system consisting of 2

capillary systems connected by a vein• Lies between hypothalamus and anterior pituitary• Hypothalamus controls it by producing

hypothalamic releasing hormones, which stimulates the anterior pituitary gland to secrete thyroid stimulating hormone and hypothalamic inhibiting hormones, which prevent it from secreting prolactin.

• •

Anterior Pituitary Hormones

• Affecting other glands• Gonadotrophic hormones stimulate gonads (testes,

ovaries) production of gametes and sex hormones• Adrenocorticotrophic hormones stimulate adrenal

cortex leading to production of glucocorticoid• Thyroid stimulating hormones stimulate thyroid to

produce thyroxine and triiodothyronine• All involved in 3 tier system and blood level of

last hormone exerts negative feedback controls over first 2 hormones

•

Anterior Pituitary Hormones

• Not affecting other glands• Prolactin is produced but only after childbirth and causes the

mammary glands in breasts to develop milk to nurse babies. It also plays a role in carb and fat metabolism

• Growth hormone (aka somatotrophic hormone) helps with skeletal and muscle growth. It stimulates the rate amino acids enter cells and how quickly protein synthesis occurs. Also promotes fat metabolism

• Melanocyte stimulating hormones cause skin color changes in fish, amphibians, reptiles which have melanophores, special skin cells that help produce color variations. Low concentration in humans

Anterior Pituitary Hormones

• Effect of Growth Hormone• Made by anterior pituitary gland after being stimulated by releasing

hormone from hypothalamus • It is released the most during childhood when the body is growing

the most• If it too little is produced it can lead to pituitary dwarfism where

people have normal proportions but a small structure• Characterized by low blood sugar because GH is responsible for opposing

effect of insulin but since they lack this is, it doesn’t occur as often• Too much can cause someone to be a giant and they have poor

health because too much GH cancels out the effects of insulin, leading to diabetes mellitus

• If overproduced in adults, acromegaly can occur when is when areas such as the chin, nose and eyebrow ridges become large

Thyroid Gland

• Located in the neck, attached to trachea just below larynx

• Largest gland, weighing 20g• Red with 2 lobes connected by

slender isthmus• It is composed of large number

of follicles each with a small spherical structure made of thyroid cells filled with thyroid hormones, triiodothyronine and thyroxine

Thyroid• To produce the hormones, it needs iodine• Without iodine in the diet, the thyroid is unable to produce its

hormones • In response to stimulation by anterior pituitary gland, the

thyroid can become enlarged resulting in simple gioter.• The hormones don’t target a specific organ, but stimulate all

the cells in the body to help it metabolize faster so more glucose is broken down and more energy is used.

Thyroid• If development doesn’t occur properly, congenital

hypothyroidism occurs where are people are short and stocky and don’t develop as well as others• Thyroid hormone treatment is used, but if not treated within first

2 months of life, it can lead to mental retardation• This can occur in adults and is called myxedema, characterized by

lethargy, weight gain, loss of hair, slow pulse, thick/puffy skin• Hyperthyroidism or Graves Disease is when the thyroid gland

is overactive andexophthalmic gioter is formed, causing eyes to stick out because of swelling of muscles in eyes and edema in eye socket• Leads to insomnia, nervousness• Can also be caused by thyroid tumor

Thyroid• Calcium• Used for nervous conduction, muscle contraction, blood clotting • Blood calcium levels are regulated by calcitonin, secreted when

blood hormone levels rise• A low level of calcium blood level causes parathyroid hormones

to be secreted

Parathyroid Glands• 4 of them• They cause blood phosphate levels to decrease and blood

calcium level to increase when it is low• Promotes activity of osteoclasts, release of calcium from bones,

reabsorption by kidneys so it isn’t secreted• Activates vitamin d which leads to calcium being absorbed form

intestine• Insufficient amounts can lead to Tetany: body shaking from

muscle contraction because of increased excitability of nerves

Antagonistic Hormones• Calcitonin and PTH are this because they do opposite things

but work to regulate calcium levels in blood• Both are released when blood calcium levels are low

Adrenal Glands• On top of kidneys consisting of adrenal medulla and adrenal cortex• Hypothalamus controls secretion ACTH which stimulates adrenal

cortex to secrete glucocorticoids.• Stimulated by hypothalamus when people are under stress• Adrenal medulla produces epinephrine and norepinephrine which

are responsible for how the body reacts in emergency situations• Accelerates breakdown of glucose forming ATP, mobilizing glycogen

and increasing cardiac rate• Short term

• Adrenal cortex produces mineralocorticoids, regulating salt and water balance and glucocorticoids regulating carb, protein and fat metabolism leading to increase in blood glucose levels• Also produces small amount of sex hormones for males and females

Adrenal Glands• Glucocorticoids• Cortisol: raises blood glucose levels by promoting breakdown of muscle

proteins to amino acids, taken up by liver, turning amino acids into glucose. Also promotes metabolism of fatty acids rather than carbs• Can be administered in form of cortisone to help with inflammation and arthritis

• Mineralocorticoids• Aldosterone: targets kidneys promoting renal absorption of sodium and ran

excretion of potassium• Not controlled by anterior pituitary• When blood sodium levels low, renin secreted by kidneys, converting plasma

protein angiotensinogen to angiotensin 1, then to angiotensin 2, stimulating adrenal cortex to release aldosterone• Called renin-angiotensin-aldosterone system: raises blood pressure by

angiotensin 2 constricting arterioles and aldosterone causing kidneys to reabsorb sodium.

• Antagonistic hormone: atrial natriuretic hormone which inhibits secretion of aldosterone from adrenal cortex. causes excretion of sodium, natriuresis

Adrenal Cortex• Diseases caused by malfunctioning• Addison: excessive ACTH causes bronzing of skin because of

buildup of melanin• Weightloss, hypertension

• Cushing Syndrome: level of adrenal cortex is high and excess cortisol builds up in tendency towards diabetes.• Trunk obese, excess aldosterone and reabsorption of sodium leading

to basic blood pH.

Testes and Ovaries• Testes: in scrotum, produce androgens (male sex hormones)• Ovaries: pelvic cavity, produce estrogen and progesterone

(female sex hormones)• Anterior pituitary gland release gonadotrophic hormones,

controlling secretions of testes and ovaries.• Testorene growth of male reproductive parts, hair, enlarges

larynx and vocal cords, make up anabolic steroids, stimulates sweat and oil glands, baldness

• Estrogen and progesterone growth of female reproductive parts, egg maturation, more fat accumulation, breast development and uterine cycle, large pelvic cavity

Pineal Gland• Located in brain, produces melatonin at night• Relates to our circadian rhythms• Regulates sexual development as well

Thymus Gland• Lobular gland, beneath sternum, largest, most active size

during childhood.• As we age, it becomes smaller and fatty• Lymphocytes from bone marrow go through this and form T

lymphocytes • Lines by epiphelial cells that secrete thymosins• Hormones primarily work only here, but could be possibly

used to help people with AIDS and cancer

• Leptin: secreted by adipose tissue and has role in feedback connection of appetite. Binds to neurons in CNS and can make people feel satiation and suppress appetite

• Erythropoietin: produced by kidneys in response to low oxygen levels, stimulates production of red blood cells and it can cause bone marrow to produce red blood cells at 30 million a second. • Can help with anemia, cancer, aids• Blood can become thicker, blood pressure can elevate

• Prostaglandins: local hormones that are produced within cells from arachidonate, a fatty acid. Can cause muscle to contract when women are menstrating.• Can reduce gastric secretion, treat ulcers, lower blood pressure,

inhibit platelet aggregation and prevent thrombosis