Download - The Endocrine Glands & their Hormones PART I. The Endocrine Glands & their Hormones Basic principles in hormone actions: Many effects of one hormone are

The Endocrine Glands & their Hormones

PART I


Basic principles in hormone actions:

Many effects of one hormone areantagonized by another hormone

This helps maintain HOMEOSTASIS


Pineal 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).


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.-Calcitonin

Acts by reducing calcium levels


Parathyroid Gland

-Parathyroid Hormone

Raises Blood Calcium

(antagonize Calcitonin)

This hormone acts on bone, kidneyand the gut


Thymus 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


Heart

-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


Gastrointestinal Hormones

-The mucosa of the GI tract secretes a dozen PEPTIDE hormones3 most important:1. Secretin : Secreted in the small intestine

Stimulates the secretion ofpancreatic bicarbonate and hasother functions on digestion

2. Gastrin: Secreted in the walls of stomachStimulate hydrochloric acid secretionstimulate pancreatic enzyme secretion

3. Cholecystokinin : Secreted in the small intestineStimulate gall bladder contractionStimulate pancreatic enzyme secretion


Pancreas

Endocrine 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 & Diabetes

Insulin & Diabetes

Diabetes : Hyperglycemia, ie. Elevated Blood Sugar

2 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 dailybasis

Type 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


Adrenal Glands

2 parts : Medulla & Cortex

Adrenal Cortex : 3 categories of steroidhormones

1. Mineralocorticoids2. Glucocorticoids3. Sex Steroids

Adrenal Medulla1. Adrenaline2. Noradrenaline


Adrenal Cortex

If 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.

Androgen

Estrogen

Influence sexual differentiationand bodily changes during puberty


Adrenal Medulla

Adrenaline : 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…)


Gonads ; Testes

The 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


Gonads ; Ovaries

2 major classes of hormonesESTROGENSPROGESTINS

Primary ESTROGEN : Estradiolothers : Estriol

EstroneSynthetic estrogens : Birth control pillsEstrogens : -Development of sexual

characteristics at puberty -Influence metabolic rate -Influence sexual and maternal behavior


Gonads ; Ovaries

PROGESTIN : 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.


Placenta

-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 II

The Pituitary Gland & its Hormone

Also calledthe HYPOPHYSIS


-Attached to the HYPOTHALAMUS

-Secretion of the pituitary hormones is regulated by hypothalamus

-HYPOTHALAMIC-PITUITARY connection


ANATOMY

-3 parts

--> Anterior Lobe-pars distalis

--> Intermediate Lobe-pars intermedia

--> Posterior Lobe-pars nervosa (“neural” cells)direct extensionof the hypothalamus

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Attaches the hypothalamus to thepituitary. Also calledthe Infundibulum

Neurohypophysis

-Neuroscretory Cells -Paraventricular nucleus (PVN) -Supraoptic nucleus (SON)

-Hormones secreted

-OXYTOCIN-VASOPRESSIN

PVN SON

AXONS



Neurohypophysis

PVN SON

AXONS

OXYTOCIN & 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

--> Neurophysins



Neurohypophysis

PVN SON

AXONS



Adenohypophysis

AXONS

ADENOHYPOPHYSIS (ANTERIOR)

Mechanism for release of hormones

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


Median eminence

1. 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.



Adenohypophysis

AXONS

Adenohypophysis : 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.



Adenohypophysis

AXONS


2. Adrenocorticotropic HormoneACTH

Role : Stimulates synthesis andrelease of glucocorticoidhormones

‘Hypothalamic-pituitary-adrenalaxis’

1970’s : Role of memory….little problems…..



Adenohypophysis

AXONS


3. Thyroid Stimulating HormoneTSH

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



Adenohypophysis

AXONS

Adenohypophysis : 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



Adenohypophysis

AXONS


5. Luteinizing hormone (LH)

Role :

Female : Stimulates ovulation and formation of progesterone- secreting cells

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



Adenohypophysis

AXONS


6. Prolactin (PRL)

Role : Initiates milk synthesis inmammary glands

Other functions related to growth & parental behavior

Interaction with serotonin also(important in depression)



Adenohypophysis

AXONS

Non 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


Beta-Endorphin : Role to play in --> Analgesia--> Learning and Memory--> Psychiatric diseases--> Feeding, Thermoregulation,--> Blood pressure--> also called the ‘drug of the jogger’…..



Pars Intermedia

AXONS

Pars 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 & Sunshine

MSH…..

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



Download - The Endocrine Glands & their Hormones PART I. The Endocrine Glands & their Hormones Basic principles in hormone actions: Many effects of one hormone are

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