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The Endocrine Glands & their HormonesPART I

The Endocrine Glands & their HormonesBasic principles in hormone actions:

Many effects of one hormone areantagonized by another hormone

This helps maintain HOMEOSTASIS

The Endocrine Glands & their HormonesPineal Gland-Main hormone secretedMELATONIN

-Role Melatonin

--Mammals : Regulate reproductive activity in response to environmental light cyclese.g. Some mammals mate in summer (lot of light), while others mate in winter (low light).

The Endocrine Glands & their Hormones

Thyroid Gland-Produces 3 main hormones-Triiodothyronine (T3)-Thyroxine (T4)Regulate body metabolism and areimportant in bone growth and maturationof the brain-Congenital lack of thyroid hormones:Cretinism.-CalcitoninActs by reducing calcium levels

The Endocrine Glands & their HormonesParathyroid Gland-Parathyroid HormoneRaises Blood Calcium

(antagonize Calcitonin)

This hormone acts on bone, kidneyand the gut

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The Endocrine Glands & their HormonesThymus Gland-Thymosin : Stimulates the production of Lymphocytes

-Thymostatin : Inhibits the production of Lymphocytes

Thymus : Important for the neonatalproduction of antibodies

Thymus : Gland being at the centerof endocrine, neural, and immunesystems

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The Endocrine Glands & their HormonesHeart-Granular cells in the heart musclesecrete Atrial Natriuretic Factor (ANF)

..ANF : Regulates blood pressure,blood volume, and excretionof water, sodium andpotassium

..ANF : Also a neuropeptide in the brain

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The Endocrine Glands & their HormonesGastrointestinal Hormones-The mucosa of the GI tract secretes a dozen PEPTIDE hormones3 most important:1. Secretin : Secreted in the small intestineStimulates the secretion ofpancreatic bicarbonate and hasother functions on digestion2. Gastrin: Secreted in the walls of stomachStimulate hydrochloric acid secretionstimulate pancreatic enzyme secretion3. Cholecystokinin : Secreted in the small intestineStimulate gall bladder contractionStimulate pancreatic enzyme secretion

The Endocrine Glands & their HormonesPancreasEndocrine cells in the pancreas secrete2 major types of hormones

1. Insulin : Secreted in response to increase in blood glucose levels ;So insulin LOWERS glucose levels byINCREASING glucose UPTAKE in cellswhere it is stored as glycogen.2. Glucagon : Increases blood glucoselevels by stimulating the conversionof glycogen to glucose in the liver.

A parte : Insulin & DiabetesInsulin & DiabetesDiabetes : Hyperglycemia, ie. Elevated Blood Sugar2 Types : The distinction is based uponwhether the blood sugar problem iscaused by insulin deficiency (Type 1)or insulin resistance (Type 2)Type 1- Insulin Deficiency : There is notenough insulin produced by the pancreasso the patient must inject insulin on a dailybasisType 2 - Insulin Resistance : There is plenty ofinsulin but the cells of the body are resistantto its action so, increase in blood sugarThis form is controlled by a strict diet

The Endocrine Glands & their HormonesAdrenal Glands2 parts : Medulla & Cortex

Adrenal Cortex : 3 categories of steroidhormones1. Mineralocorticoids2. Glucocorticoids3. Sex Steroids

Adrenal Medulla1. Adrenaline2. Noradrenaline

The Endocrine Glands & their HormonesAdrenal CortexIf there is a sodium deprivation,Aldosterone is secreted and actsto increase reabsorption ofsodium ions (NA+) in the kidneyssalivary glands, and sweat glands.Stress Hormone, converts storedproteins to carbohydrate during stress.Antiinflammatory andImmunosuppressive functions.AndrogenEstrogenInfluence sexual differentiationand bodily changes during puberty

The Endocrine Glands & their HormonesAdrenal MedullaAdrenaline : Released followingstress due to environmental extremes; Increases heartrate and blood glucose levelsso, increases the amount of workthe muscles can do (FLIGHT)Noradrenaline : As Adrenaline, act as a NTin the brainPeriphery; increase blood pressureand constrict blood vessels(noradrenaline, stress, and heart disease)

The Endocrine Glands & their HormonesGonads ; TestesThe male gonads : produces Androgens

Primary androgen = TESTOSTERONEOther androgen : Dihydrotestosterone Androstenedione

Testosterone : Important for masculinizationControl of sperm productionDevelopment of male sexualcharacteristicsActivation of sexual and aggressive behaviors

The Endocrine Glands & their HormonesGonads ; Ovaries2 major classes of hormonesESTROGENSPROGESTINS

Primary ESTROGEN : Estradiolothers :EstriolEstroneSynthetic estrogens : Birth control pillsEstrogens : -Development of sexualcharacteristics at puberty -Influence metabolic rate -Influence sexual and maternal behavior

The Endocrine Glands & their HormonesGonads ; OvariesPROGESTIN : Progesterone

-Stimulates breast and uterine enlargement at puberty & during menstrual cycle-Maintains pregnancy (inhibits menstrualcycle during pregnancy)

Other hormone released at the end ofpregnancy : RelaxinActs to prepare the birth canal.Estrogen and Progesterone act in synergy.

The Endocrine Glands & their HormonesPlacenta-Hormones secreted by the fertilized egg(Used in pregnancy tests)

Human Chorionic Gonadotropin (HCG)Act by keeping progesterone high at thebeginning of a pregnancy

Human Placental Lactogen (HPL)Stimulates the mammary glands to beginto secrete milk

PART IIThe Pituitary Gland & its HormoneAlso calledthe HYPOPHYSIS

The Pituitary Gland & its Hormone-Attached to the HYPOTHALAMUS

-Secretion of the pituitary hormones is regulated by hypothalamus

-HYPOTHALAMIC-PITUITARY connection

The Pituitary Gland & its HormoneANATOMY

-3 parts

--> Anterior Lobe-pars distalis

--> Intermediate Lobe-pars intermedia

--> Posterior Lobe-pars nervosa (neural cells)direct extensionof the hypothalamusADENOhypophysisNEUROhypophysis

The Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumNeurohypophysis-Neuroscretory Cells -Paraventricular nucleus (PVN) -Supraoptic nucleus (SON)

-Hormones secreted

-OXYTOCIN-VASOPRESSINPVNSONAXONS

The Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumNeurohypophysisPVNSONAXONSOXYTOCIN & VASOPRESSIN-Are really HYPOTHALAMIC hormones

-OXYTOCIN :

2 main functions

--> promotes uterine contractions --> stimulates milk ejection from mammary glands during lactation

-VASOPRESIN :

--> Antidiuretic hormone --> Raises blood pressure --> promotes water reabsorption by kidneys --> centrally : may promote memory

- Binding proteins for both oxytocin & vasopressin

--> NeurophysinsThe Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumNeurohypophysisPVNSONAXONS

The Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumAdenohypophysisAXONSADENOHYPOPHYSIS (ANTERIOR)

Mechanism for release of hormones

True endocrine gland because release hormone in the bloodstream(hypophysal portal system)

The Pituitary Gland & its HormoneMedian eminence1. Neurosecretory cells of the hypothalamus release their hormones at the median eminence

2. Hormones circulate in bloodstream

3. Carried to the adenohypophysis

4. Stimulates secretion of other hormones from the adenophysis

5. These hormones are then released in the bloodstream to reach their target cells.

The Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumAdenohypophysisAXONSAdenohypophysis : 6 hormones

1. Growth Hormone (GH) (also called somatotropin) tropic=stimulating effect

GH = promotes growth in almost all body cells

A lot of attention for degenerativedisease..-Alzheimer-Parkinson-Anti-Aging etc.


2. Adrenocorticotropic HormoneACTH

Role : Stimulates synthesis andrelease of glucocorticoidhormones

Hypothalamic-pituitary-adrenalaxis

1970s : Role of memory.little problems..


3. Thyroid Stimulating HormoneTSH

Role : Stimulates the synthesis andrelease of thyroxine (T4)and triiodochyronine (T3)from the thyroid.

The Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumAdenohypophysisAXONSAdenohypophysis : 6 hormones3 last hormones= .gonadotropic hormones

4. Follicle stimulating hormone (FSH)

Role : In both sexes, promotes thedevelopment of reproductivecells (gametes) and promotes secretion ofgonadal hormones

Males : stimulates sperm productionFemales : stimulates growth of primary follicle of ovary


5. Luteinizing hormone (LH)

Role :

Female : Stimulates ovulation and formation of progesterone- secreting cells

Males : Stimulates cells that secrete androgens (e.g. testosterone)


6. Prolactin (PRL)

Role : Initiates milk synthesis inmammary glands

Other functions related to growth & parental behavior

Interaction with serotonin also(important in depression)

The Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumAdenohypophysisAXONSNon traditional hormone from theadenohypophysis

--> beta-endorphin

Derivative from POMC

POMC : synthesized in the parsdistalis and pars intermedia

Broken down into ACTH, MSH &beta-endorphins by enzymes

The Pituitary Gland & its HormoneBeta-Endorphin : Role to play in --> Analgesia--> Learning and Memory--> Psychiatric diseases--> Feeding, Thermoregulation,--> Blood pressure--> also called the drug of the jogger..

The Pituitary Gland & its HormoneAttaches the hypothalamus to thepituitary. Also calledthe InfundibulumPars IntermediaAXONSPars Intermedia :

Not present in adult humans butpresent in fetal humans and mammals

Synthesize the hormone calledMelanocyte stimulating hormoneswhich acts in amphibian to changeskin color.

Our friend Watson :Sex & SunshineMSH..

http://www.psych.mcgill.ca/courses/342/h&b.htm

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