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The Endocrine System Contributes to: control of growth, development, reproduction, behaviour, energy metabolism, and water balanceBy:Secreting hormones To controlOrgan and tissue functions

Endocrine SystemA system of ductless secretory organs (glands) located in various parts of the bodyIncludePinealAnterior/posterior pituitary Thyroid Parathyroid Thymus Adrenal Islets of Langerhans, Ovaries TestesMain functionSecrete hormones directly into the blood or extracellular fluid

Hypothalamus Is not a gland but a region of the brainPart of the nervous system Very important for function of endocrine system Produce neurohormones that stimulate or inhibit production of other hormones in the pituitary gland

Hormones of The HypothalamusThyrotropin-releasing hormone (TRH)Stimulates release of thyroid-stimulating hormone (TSH)Gonadotropin-releasing hormone (GnRH)Stimulates release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)Growth hormone-releasing hormone (GHRH)Stimulates release of growth hormone (GH)Corticotropin-releasing hormone (CRH)Release of adrenocorticotropic hormone (ACTH)SomatosinInhibits the release of growth hormone (GH)DopamineInhibits the release of prolactin

Hormones: Maintaining Homeostasis Chemical management system for the body Chemicals produced by cells in one part of the body that regulate the processes of cells in another part of the bodyChemical messengers act on cells from another part of the body Local regulators (paracrine)act on nearby cells Self regulators (autocrine) cells that produce chemicals to stimulate their own cellular processes

Tropic vs Non-Tropic HormonesTropic HormonesTarget endocrine glands Nontropic Hormones Target cells, tissues, and organs

Hormones Produced and secreted by cells, tissues and organs that compose the endocrine system (glands) directly into the blood or extracellular fluidHormones are circulated throughout the bodyOnly target cells will respond to specific hormones Hormones are broken down by enzymes in target cell, liver or kidneys where they are reused or excreted

Hormones Secreted in an inactive form prohormonesProhormones are converted by target cells or by enzymes in the blood to an active formAngiotensinogen angiotensin

Hormones Protein hormones Consist of AA (3 to 200 in length)Usually hydrophilic (water soluble)Diffuse well through bloodCannot pass through lipid bilayer Steroid hormones Derived from cholesterol Not water solubleUsually encased with protein (protein carrier) to travel through bloodPass easily through lipid bilayer

Hormone Mechanisms Water-Soluble Cannot pass membraneBind to receptor molecules in the cell membrane Signal is activatedSecondary messenger is activated (cAMP cyclic adenosine monophosphate) Change is caused inside cellActs in the cytosol or the nucleusRegulate protein production, ion channelsActivation of protein kinases GlucagonBreakdown of glycogen into glucose

Controlling Blood Glucose Levels Controlling Blood Glucose Levels

Hormone Mechanisms Lipid-Soluble Can pass membrane (lipid)Bind to receptors inside a cell (cytosol or nucleus)Turn on or off an action of a specific geneChanges amount of protein that is synthesized by cell Aldosterone Increase sodium absorption increases water retention increase blood pressure

Major Features of Hormone Mechanisms Only the cells that contain surface or internal receptors for the hormones respond to the hormones Once bound to their receptors, hormones produce a response by turning cellular processes on or off. They do this by altering the proteins that are functioning in or produced by the cellHormones are effective in very small concentrations because of the amplification that occurs in both the surface and internal receptor mechanismsThe response to a hormone differs among target organs and among species

Hormones: Negative Feedback MechanismsSecretion of hormones are regulated by negative feedback mechanisms Hormones inhibit other hormonesMultiple hormones can be secreted at a time

The Pituitary GlandThe Master GlandProduces hormones that control most of the other glands in the endocrine systemMade up of anterior lobe and posterior lobeLinks endocrine system to nervous system via portal vein (hypothalamus)Influenced by hypothalamus Releasing hormones/inhibiting hormones

2. portal vein4. anterior pituitary gland5. hypophyseal vein6. posterior pituitary gland8. pituitary stalk9. capillary network10. neurons11. neurosecretory cells12. hypothalamus Anterior Pituitary GlandMajor hormones secreted into the bloodstreamTropic Growth hormone (both)thyroid-stimulating hormoneadrenocorticotropic hormone follicle-stimulating hormone luteinizing hormoneNontropic ProlactinMelanocyte-stimulating hormone

Prolactin

Promote milk production in mammary glandsSuckling on nipple causes stimulus Regulated by dopamine Too much HyperprolactinaemiaToo littleHypoprolactinaemia Growth hormoneCell division, protein synthesis, bone growth Release of growth hormone stimulates release of IGF in liver (insulin growth factor) that stimulates these functions Conversion of glycogen to glucose, fats to fatty acids regulates levels in bloodStimulates cells to take up FA, AA and limits muscle cells to take up glucose

Growth hormone Underproduction DwarfismHeart disease, increased fatCauseGenetic, benign tumour on pituitary glandOverproduction Acromegaly body tissues get larger over timeGigantism excessive production of growth hormoneCauseBenign tumour on pituitary gland

Thyroid-stimulating hormone

Controls production of the thyroid hormones Overproduction HyperthyroidismCauseThyroid is producing too much thyroid hormone Underproduction Hypothyroidism Cause Thyroid if producing not enough thyroid hormone Adrenocorticotropic hormone

Controls production of cortisol, adrenaline, noradrenalineUnderproduction Cushings syndrome CauseSteroid medication, tumour of pituitary gland Overproduction Cushings disease Addisons disease (loss of function of cortex of adrenal gland)Cause Adenoma (non-cancerous tumour) in the pituitary glandAutoimmunity Follicle-stimulating hormone/luteinising hormone

Puberty development/function of the gonads (testes/ovaries)Sex steroid production Germ cell production (sperm/eggs)Underproduction Incomplete development at puberty Infertility Overproduction Turner syndrome (female is missing entire/parts of x chromosome)Kallmanns syndrome (failure to start/complete puberty) Cause Testicular/ovarian failure, Melanocyte-stimulating hormoneCauses darkening in humans by releasing melanin in the skin and hair and eyesSpecialized cells called melanocytes release melaninProtects from UV raysOverproduction Increase production of melanin CauseProlonged exposure to sun or skin tanningUnderproduction Lack of skin pigmentation Loss of natural protection from UV rays and sun Cause Damage to pituitary glands

Posterior pituitary glandStores and releases 2 major hormones into the bloodstreamAntidiuretic hormone (vasopressin)oxytocinThese hormones are produced by the hypothalamus and stored here

Antidiuretic Hormone (vasopressin)Causes distal convoluted tubule to become permeable to waterHelps maintain water balanceOverproduction Kidneys retain too much waterUnderproductionKidneys excrete too much water

Oxytocin

Contraction of the wombLactationOverproductionNot clear UnderproductionLinked to autism Thyroid glandLocated in the front of the throat and shaped like a bow tieSecretes Thyroxine (T)calcitonin

Thyroxine (T)Prohormone (inactive) Active form is triiodothyronineContains 4 iodine atomsRegulates bodys metabolic rate, heart and digestive function, muscle control, brain development, maintenance of bones Overproduction Thyrotoxicosis too much thyroxine in bloodstream recognized by goitreCausesHyperthyroidism Graves Disease UnderproductionHypothyroidism Causes Autoimmune diseases, poor iodine diet

CalcitoninReduces levels of Calcium (Ca) in the blood stream Opposes the action of parathyroid hormoneOverproductionNo apparent effect on body Underproduction No apparent effect on body

Parathyroid gland4 spherical glands (size of a pea) located on each side of the posterior surface of the thyroid glandSecretes Parathyroid hormone

Parathyroid hormoneStimulates enzymes in kidneys to convert vitamin D into calcitrol increasing absorption of Ca and phosphates from foodUnderproductionMuscle crampsOsteoporosisOverproductionKidney stones

Pineal glandLocated near the centre of the brain Secretesmelatonin Secretion of melatonin is controlled by circadian rhythm (biological processes that fluctuate on a 24 hour timetable)Helps to synchronize biological clock (jet lag, sleep disorders) Melatonin also produced in retina of the eyeOverproduction Reduced core body temperatureUnderproductionNo apparent effect on the body

Adrenal glandsConsist of two regionsAdrenal medullacontains highly modified neuro-secretory neurons2. Adrenal cortexcontains non-neural endocrine cells

Adrenal medullaSecretes Epinephrine, nor-epinephrineThese chemicals can act as hormones or neurotransmitters (transmit nerve signals to brain)Part of the fight or flight response

EpinephrineReleased when body encounters stressesIncrease heart rate glycogen and fat breakdownMajor blood vessels dilate (increase blood flow)Blood vessels in skin constrict (chills and sweating)Increase in blood pressure Reduces water lossDigestive system slowsUsed to counter anaphylaxis

Adrenal cortex Secretes Aldosterone, cortisol

GlucocorticoidsCortisol Helps raise blood glucose levels using three mechanismsStimulate synthesis of glucose from fats and proteinsReduce glucose uptake by the body cells except in the central nervous system Promote breakdown of fats and proteins into fatty acids and amino acids as alternative fuels

MineralocorticoidsAldosterone Increase amount of sodium /water reabsorption in bloodstreamIncrease amount of potassium removal in urineIncrease blood pressure Overproduction High blood pressure, low potassium, alkaline blood Causes Adrenal tumour Underproduction Addisons disease, low blood pressure

Regulating blood sugar Occurs automatically in our body Pancreas contain both exocrine and endocrine glandsExocrine secretes digestive enzymes into the small intestineEndocrineIslets of Langerhans - Secretes insulin (beta cells) and glucagon (alpha cells)

Insulin/GlucagonRegulate the ability of most tissues in the body to metabolize fuel substances (glucose, fats, proteins)

InsulinSecreted by beta cells Lower blood glucose levels by Acts on skeletal muscles, liver cells, adipose tissue (fat) to uptake glucoseIn the LiverLowers fatty acid levels promotes fatty acid uptake and storage in adipose tissueInhibits breakdown of fats into fatty acidsLowers amino acid levels Promotes protein synthesis Inhibits breakdown of proteins

GlucagonSecreted by alpha cells Increase blood glucose levels byStimulating breakdown of glycogen into glucoseStimulates breakdown of fats into fatty acids Stimulates breakdown of proteins into amino acids Stimulate cells to use amino acids and non-carbohydrates to synthesize glucose

Glucose levels throughout the day

Unstable levels of glucoseHyperglycemia (above 200mg/dL of blood)Blood glucose levels are too high (norm 115-200mg/dL)SymptomsFrequent urination, sugar in the urine, vision problems, fatigue, weight lossHypoglycemia (below 70mg/dL of blood)Blood glucose levels are too low(norm 70-115mg/dL)Symptoms Nervousness, cold sweats, hunger, headaches, weaknessDiabetesHigh glucose levels in the blood caused by problems with insulin productionSymptomsFrequent urination, increased thirst/appetite Classified into 3 different typesType 1Type 2Gestational

Type 1Also called juvenile diabetes or insulin-dependantBeta cells do not produce any insulinDaily administration of insulin is required usually by injection or pump

Type 2Reduced insulin production or the inability of insulin to bind to its receptors properly Developed in adulthood and is associated with obesity 90% of diabetics have this typeControlling diet and exercise helps restore normal levels of insulin production

Gestational Occurs in about 2 to 10% of pregnant womenHigh blood glucose levels develop during pregnancyUsually a temporary condition but does increase the risk of both mother and child developing later in life

Reproductive Hormones

Gonads (sex glands) Males testesFemales ovaries Sex hormones Androgens, estrogens, progestinsRegulate development of male and female reproductive systems, sexual characteristics, mating behaviour

Female Reproductive System Pair of ovaries Located in abdominal cavity Produce female gametes (ova, eggs)Produce estrogen and progesteroneFSH and LH from the pituitary gland stimulate the maturation of the follicles in the ovary and trigger ovulation

Estrogen EstradiolStimulates maturation of the sex organs at pubertyRelease of egg during ovulation Development of secondary sexual characteristics (breast development, body hair, widening of pelvis)Sex drive

Progestins Progesterone Secreted by the corpus luteum in the ovary Maintains uterus for implantation of a fertilized eggGrowth and development of an embryo

OogenesisProduction and release of eggs (ova) by the ovariesReleases oocytes - immature eggs that have undergone 1 meiotic divisionPolar body is associated with itDisintegrates quickly Females produce up to 1 millionOnly ~380 are ovulated before menopause

Ovulation Monthly release of one or a few developing oocytes into the oviductBurst of LH causes follicle to rupture Ova becomes ovumMoves through the oviduct (fallopian tubes) via cilia that line these tubesFertilization occurs here in the oviductundergoes second meiotic division only if penetrated by sperm cell producing a zygoteIf not fertilized egg will degenerate

Ovarian cycle Occurs from puberty to menopause Involves release of a mature egg approx every 28 daysCoordinated with the menstrual cycle (month)Prepares the uterus to implant the egg if fertilization occurs

Corpus luteum LH causes ruptured follicle to grow into an enlarged yellowish structureInitiates luteal phase prepares uterus to receive an eggIf egg is fertilized:Acts as an endocrine gland- secretes estrogens, progesterone and inhibinProgesterone inhibits GnRH FSH LHInhibin prevents secretion of FSHIf egg is not fertilizedCorpus luteum shrinks

Menstrual cycle Begins at day 0Results from the breakdown of the endometrium Releases blood and tissue breakdown products from the uterus to the outside through the vaginaDay 4 or 5 flow ceases and endometrium begins to grow againSame hormones that control ovarian cycle control this cycle

MenopauseHigh levels of sex hormones stopsLate 40s or early 50sMenstrual/Ovarian cycle stops Side effectsHot flashes, headaches, mood swingsTreated with HRT (hormone replacement therapy)

Male reproductive system TestesAffect the development of male secondary characteristics Secrete androgens (testosterone)Stimulates puberty, facial hair, vocal cords, sex driveSpermatogenesis production of spermRelease of testosterone in the body is controlled by LH which is controlled by GnRH

SpermatogenesisSperm development from spermatogoniaTakes about 9 to 10 weeks - spermatogonium to spermTestes produce about 130 million fertile sperm each day

SpermatogenesisLeydig cells - secrete testosterone Sertoli cells supply nutrients to spermatocytes and seal them off from bodys blood supply Coiled seminiferous tubules located in epididymis store mature spermVas deferens transport sperm upon ejaculation